when does genetic recombination occur (select all that apply.)
DNA


chromosomal crossover which occurs during sexual reproduction, when genetic recombination occurs. Chromosomal crossover is when two DNA helices break, swap a section and then rejoin. Recombination allows chromosomes to exchange genetic information and produces new combinations of genes, which increases the efficiency of natural selection and can be important in the rapid evolution of new proteins. Genetic recombination can also be involved in DNA repair, particularly in the cell's response to double-strand breaks. The most common form of chromosomal crossover is homologous recombination, where the two chromosomes involved
8040244
Genetically modified food


defined as organisms (i.e. plants, animals or microorganisms) in which the genetic material (DNA) has been altered in a way that does not occur naturally by mating and/or natural recombination. The technology is often called 'modern biotechnology' or 'gene technology', sometimes also 'recombinant DNA technology' or 'genetic engineering'. ... Foods produced from or using GM organisms are often referred to as GM foods." Human-directed genetic manipulation of food began with the domestication of plants and animals through artificial selection at
2963168
Natural selection


on the strength of the natural selection, which is a function of how unfavourable the mutation proves to be. Genetic linkage occurs when the loci of two alleles are in close proximity on a chromosome. During the formation of gametes, recombination reshuffles the alleles. The chance that such a reshuffle occurs between two alleles is inversely related to the distance between them. Selective sweeps occur when an allele becomes more common in a population as a result of positive selection. As the prevalence of one allele increases, closely linked alleles can also
1233561
Somatic recombination


Somatic recombination, as opposed to the genetic recombination that occurs in meiosis, is an alteration of the DNA of a somatic cell that is inherited by its daughter cells. The term is usually reserved for large-scale alterations of DNA such as chromosomal translocations and deletions and not applied to point mutations. Somatic recombination occurs physiologically in the assembly of the B cell receptor and T-cell receptor genes (V(D)J recombination), as well as in the class switching of immunoglobulins. Somatic recombination is also important in the process of carcinogenesis
10737686
Genetics of social behavior


have been derived by comparing quality of genomic processes. Also applying to "A. mellifera"; by looking at the degree of genetic linkage and chromosomal recombination rates, light may be shed on the consequence of group selection on a eusocial insect colony. Within the Order Hymenoptera, primitively and highly eusocial species tend to have greater gene linkage and significantly higher more DNA recombination events than non-social species. This trend continues within groups of eusocial species, highly eusocial species have highly recombinant genomes. While contested, recombination activity might originate
15189325
Evolution


Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes that are passed on from parent to offspring during reproduction. Different characteristics tend to exist within any given population as a result of mutation, genetic recombination and other sources of genetic variation. Evolution occurs when evolutionary processes such as natural selection (including sexual selection) and genetic drift act on this variation, resulting in certain characteristics becoming more common or rare within a population. It is this process of evolution that has given
9155790
Penicillium


pathogen, was also previously assumed to reproduce exclusively by asexual means. This assumption was largely based on the highly clonal population structure of this species. However, recent work has revealed that the genes required for meiosis are present in "P. marneffei". This and other evidence indicated that mating and genetic recombination does occur in this species. It was concluded that "P. marneffei" is sexually reproducing, but recombination is most likely to occur across spatially and genetically limited distances in natural populations resulting in a highly clonal population structure.
2141982
Homologous chromosome


until anaphase. Genetic crossing-over, a type of recombination, occurs during the pachytene stage of prophase I. In addition, another type of recombination referred to as synthesis-dependent strand annealing (SDSA) frequently occurs. SDSA recombination involves information exchange between paired homologous chromatids, but not physical exchange. SDSA recombination does not cause crossing-over. In the process of crossing-over, genes are exchanged by the breaking and union of homologous portions of the chromosomes’ lengths. Structures called chiasmata are the site of the exchange
12126232
Selective sweep


placed into three main categories: Sweeps do not occur when selection simultaneously causes very small shifts in allele frequencies at many loci each with standing variation (polygenic adaptation). Whether or not a selective sweep has occurred can be investigated in various ways. One method is to measure linkage disequilibrium, i.e., whether a given haplotype is overrepresented in the population. Under neutral evolution, genetic recombination will result in the reshuffling of the different alleles within a haplotype, and no single haplotype will dominate the population. However, during a selective
10093026
Genetic hitchhiking


it before the hitchhiking neutral or deleterious allele becomes fixed or goes extinct. The closer a hitchhiking polymorphism is to the gene under selection, the less opportunity there is for recombination to occur. This leads to a reduction in genetic variation near a selective sweep that is greater closer to the selected site. This pattern is useful for using population data to detect selective sweeps, and hence to detect which genes have been under very recent selection. Both genetic drift and genetic draft are random evolutionary processes, i.e. they act stochastically and in
11129906
Genetic linkage


, it didn’t perform that well when applied to more common disorders such as heart disease or different forms of cancer. An explanation for this is that the genetic mechanisms affecting common disorders are different from those causing rare disorders. Recombination frequency is a measure of genetic linkage and is used in the creation of a genetic linkage map. Recombination frequency ("θ") is the frequency with which a single chromosomal crossover will take place between two genes during meiosis. A centimorgan (cM) is a unit that describes a recombination
892023
Genetic recombination


under genetic recombination. Genetic recombination and recombinational DNA repair also occurs in bacteria and archaea, which use asexual reproduction. Recombination can be artificially induced in laboratory ("in vitro") settings, producing recombinant DNA for purposes including vaccine development. V(D)J recombination in organisms with an adaptive immune system is a type of site-specific genetic recombination that helps immune cells rapidly diversify to recognize and adapt to new pathogens. During meiosis, synapsis (the pairing of homologous chromosomes) ordinarily precedes genetic recombination. Genetic recombination is catalyzed by many
331659
Gene expression programming


But the replication of strings is trivial in artificial evolutionary systems, where only an instruction to copy strings is required to pass all the information in the genome from generation to generation. The replication of the selected programs is a fundamental piece of all artificial evolutionary systems, but for evolution to occur it needs to be implemented not with the usual precision of a copy instruction, but rather with a few errors thrown in. Indeed, genetic diversity is created with genetic operators such as mutation, recombination, transposition, inversion, and many
6092416
Alveolar rhabdomyosarcoma


. In children and adolescents ARMS accounts for about 1 percent of all malignancies, has an incidence rate of 1 per million, and most cases occur sporadically with no genetic predisposition. PAX3-FOXO1 is now known to drive cancer-promoting gene expression programs through creation of distant genetic elements called super enhancers. There is no genetic predisposition for developing ARMS, but there are a few genetic recombination events that occurs to cause the fusion protein to be synthesized. In order to have the PAX3-FOXO1 fusion there needs to be a recombination event that translocates
21507839
Selection methods in plant breeding based on mode of reproduction


evaluation the remnant seed of selected full-sib families is used to recombine the best families. Asexual reproduction covers all those modes of multiplication of plants where normal gamete formation and fertilization does not take place making these distinctly different from normal seed production crops. In the absence of sexual reproduction, the genetic composition of plant material being multiplied remains essentially the same as its source plant. Clones of mother plants can be made with the exact genetic composition of the mother plant. Superior plants are selected and propagated vegetatively; the vegetative propagated
2863640
Origin and function of meiosis


numerous gene products. A key similarity between prokaryotic sex and eukaryotic sex is that DNA originating from two different individuals (parents) join up so that homologous sequences are aligned with each other, and this is followed by exchange of genetic information (a process called genetic recombination). After the new recombinant chromosome is formed it is passed on to progeny. When genetic recombination occurs between DNA molecules originating from different parents, the recombination process is catalyzed in prokaryotes and eukaryotes by enzymes that have similar functions and that are evolutionarily related.
9480488
Background selection


studies of genetic diversity. For instance, the observation that genetic diversity is weakly correlated with population size, or not correlated at all, is called the "paradox of variation". Under the theory of background selection, the paradox is resolved, because neutral variation is predicted to be purged in conjunction with deleterious mutations. Background selection also contributes to a selective explanation of the positive correlation between recombination and polymorphism across populations. In areas of high recombination, neutral loci are more likely to ‘escape' the effects of nearby selection
21162355
Neurospora crassa


from gene conversion studies and studies of the reaction capabilities of DNA. Current understanding of the molecular mechanism of recombination is discussed in the Wikipedia articles Gene conversion and Genetic recombination. An understanding of recombination is relevant to several fundamental biologic problems, such the role of recombination and recombinational repair in cancer (see BRCA1) and the adaptive function of meiosis (see Meiosis). That mating in "N. crassa" can only occur between strains of different mating type suggests that some degree of outcrossing is favored by natural selection. In haploid
15616976
Pseudoautosomal region


necessary for the normal progression of male meiosis. Thus, those cells in which X-Y recombination does not occur will fail to complete meiosis. Structural and/or genetic dissimilarity (due to hybridization or mutation) between the pseudoautosomal regions of the X and Y chromosomes can disrupt pairing and recombination, and consequently cause male infertility. The SHOX gene in the PAR1 region is the gene most commonly associated with and well understood with regards to disorders in humans, but all pseudoautosomal genes escape X-inactivation and are therefore candidates for having gene
22120020
Synapsis


such a mechanism could operate. A further consequence of recombinant synapsis is to increase genetic variability within the offspring. Repeated recombination also has the general effect of allowing genes to move independently of each other through the generations, allowing for the independent concentration of beneficial genes and the purging of the detrimental. Following synapsis, a type of recombination referred to as synthesis dependent strand annealing (SDSA) occurs frequently. SDSA recombination involves information exchange between paired non-sister homologous chromatids, but not physical exchange. SDSA recombination does not cause crossing
14002021
Interlocus contest evolution


Interlocus contest evolution (ICE) is a process of intergenomic conflict by which different loci within a single genome antagonistically coevolve. ICE supposes that the Red Queen process, which is characterized by a never-ending antagonistic evolutionary arms race, does not only apply to species but also to genes within the genome of a species. Because sexual recombination allows different gene loci to evolve semi-autonomously, genes have the potential to coevolve antagonistically. ICE occurs when "an allelic substitution at one locus selects for a new allele at the interacting
19508058
Genetic recombination


of meiosis that focus exclusively on crossing-over are inadequate to explain the majority of recombination events. Achiasmy is the phenomenon where autosomal recombination is completely absent in one sex of a species. Achiasmatic chromosomal segregation is well documented in male "Drosophila melanogaster". Heterochiasmy occurs when recombination rates differ between the sexes of a species. This sexual dimorphic pattern in recombination rate has been observed in many species. In mammals, females most often have higher rates of recombination. The "Haldane-Huxley rule" states that achiasmy usually occurs
331675
Mitotic recombination


Mitotic recombination is a type of genetic recombination that may occur in somatic cells during their preparation for mitosis in both sexual and asexual organisms. In asexual organisms, the study of mitotic recombination is one way to understand genetic linkage because it is the only source of recombination within an individual. Additionally, mitotic recombination can result in the expression of recessive genes in an otherwise heterozygous individual. This expression has important implications for the study of tumorigenesis and lethal recessive genes. Mitotic homologous recombination occurs mainly between sister chromatids subsequent to replication (but
20565510
Ectopic recombination


higher copy numbers of transposable elements and the longer lengths of those elements. Since ectopic recombination is generally deleterious, anything that increases its odds of occurring is selected against, including the aforementioned higher copy numbers and longer lengths. This model, however, can only be applied to single families of transposable elements in the genome, as the probability of ectopic recombination occurring in one TE family is independent of it occurring in another. It follows that transposable elements that are shorter, transpose themselves less often, and have mutation rates high enough
4528441
Hill–Robertson effect


In population genetics, the Hill–Robertson effect, or Hill–Robertson interference, is a phenomenon first identified by Bill Hill and Alan Robertson in 1966. It provides an explanation as to why there may be an evolutionary advantage through genetic recombination. In a population of finite size which is subject to natural selection, varying extents of linkage disequilibria will occur. These can be caused by genetic drift or by mutation, and they will tend to slow down the process of evolution by natural selection. This is most easily seen by
4160944
Illegitimate recombination


removal of a continuous segment of genetic code. However this form of mutation occurs infrequently among mutants of natural origin rather than those that have been induced. Illegitimate recombination can also occur due to the transduction of genetic material from a bacteriophage. In this case a bacteriophage will insert its genetic material into a bacteria in order to have it inserted into the bacterial genome at a point regardless of genetic homology. Another form of illegitimate recombination in prokaryotes is that of a duplication mutations of a genome. In this case a portion of the
7928985
Natural selection


Arms races are not necessarily induced by man; a well-documented example involves the spread of a gene in the butterfly "Hypolimnas bolina" suppressing male-killing activity by "Wolbachia" bacteria parasites on the island of Samoa, where the spread of the gene is known to have occurred over a period of just five years A prerequisite for natural selection to result in adaptive evolution, novel traits and speciation is the presence of heritable genetic variation that results in fitness differences. Genetic variation is the result of mutations, genetic recombinations
1233548
Sex determination in Silene


some notable examples that possess them, other than "Silene", are "Rumex, Humulus, and Cannabis". All species of "Silene" that are diploid possess the same number of chromosomes (n=12); males possess sex-determining Y chromosomes that are much larger than the X chromosomes. Recombination generally occurs only when two X chromosomes (XX) pair during female meiosis. Contrastingly, recombination is suppressed across most of the Y chromosomes during pairing in male meiosis (XY). When recombination does occur in XY
13078097
Genetic recombination


to artificial and deliberate recombination of disparate pieces of DNA, often from different organisms, creating what is called recombinant DNA. A prime example of such a use of genetic recombination is gene targeting, which can be used to add, delete or otherwise change an organism's genes. This technique is important to biomedical researchers as it allows them to study the effects of specific genes. Techniques based on genetic recombination are also applied in protein engineering to develop new proteins of biological interest. During both mitosis and meiosis, DNA damages caused
331667
Modified starch


been created by traditional cross-breeding rather than gene splicing. In Europe the term "Genetically Modified Organism" is used solely where "the genetic material has been altered in a way that does not occur naturally through fertilisation and/or natural recombination". The modification in "genetically modified" refers to the genetic engineering of the plant DNA, whereas in the term "Modified Starch" seen on mandatory ingredient labels it refers to the later processing or treatment of the starch or starch granules. Genetically modified starch is of interest in the
2371135
Endoreduplication


produced subsequent to the two meiotic divisions have the same ploidy as the somatic cells of the adult female salamander. Synapsis and recombination during meiotic prophase I in these unisexual females is thought to ordinarily occur between identical sister chromosomes and occasionally between homologous chromosomes. Thus little, if any, genetic variation is produced. Recombination between homeologous chromosomes occurs rarely, if at all. Since production of genetic variation is weak, at best, it is unlikely to provide a benefit sufficient to account for the maintenance of meiosis for millions of years.
19664178
Heterothallism


arise when strains of opposite mating type were cultured together under appropriate conditions. Sexuality generates diversity in the aflatoxin gene cluster in "A. flavus", suggesting that production of genetic variation may contribute to the maintenance of heterothallism in this species. Henk et al. showed that the genes required for meiosis are present in P. marneffei, and that mating and genetic recombination occur in this species. Henk et al. concluded that "P. marneffei" is sexually reproducing, but recombination in natural populations is most likely to occur across spatially and
7666421
Cre-Lox recombination


to manipulate a variety of genetically modified organisms to control gene expression, delete undesired DNA sequences and modify chromosome architecture. The Cre protein is a site-specific DNA recombinase that can catalyse the recombination of DNA between specific sites in a DNA molecule. These sites, known as "loxP" sequences, contain specific binding sites for Cre that surround a directional core sequence where recombination can occur. When cells that have "loxP" sites in their genome express Cre, a recombination event can occur between the "loxP" sites.
8348048
HIV


form DNA. During reverse transcription, the nascent DNA can switch multiple times between the two copies of the viral RNA. This form of recombination is known as copy-choice. Recombination events may occur throughout the genome. Anywhere from two to 20 recombination events per genome may occur at each replication cycle, and these events can rapidly shuffle the genetic information that is transmitted from parental to progeny genomes. Viral recombination produces genetic variation that likely contributes to the evolution of resistance to anti-retroviral therapy. Recombination may also contribute,
14367568
Synaptonemal complex


The synaptonemal complex (SC) is a protein structure that forms between homologous chromosomes (two pairs of sister chromatids) during meiosis and is thought to mediate chromosome pairing, synapsis, and recombination. It is now evident that the synaptonemal complex is not required for genetic recombination in some organisms. For instance, in protozoan ciliates such as "Tetrahymena thermophila" and "Paramecium tetraurelia" genetic crossover does not appear to require synaptonemal complex formation. Research has shown that not only does the SC form after genetic recombination but mutant yeast cells
9367862
Genetically modified organism


A genetically modified organism (GMO) is any organism whose genetic material has been altered using genetic engineering techniques. The exact definition of a genetically modified organism and what constitutes genetic engineering varies, with the most common being an organism altered in a way that "does not occur naturally by mating and/or natural recombination". A wide variety of organisms have been genetically modified (GM), from animals to plants and microorganisms. Genes have been transferred within the same species, across species (creating transgenic organisms) and even across kingdoms
12021472
Chromosomal crossover


Chromosomal crossover (or crossing over) is the exchange of genetic material between two homologous chromosomes non-sister chromatids that results in recombinant chromosomes during sexual reproduction. It is one of the final phases of genetic recombination, which occurs in the "pachytene" stage of prophase I of meiosis during a process called synapsis. Synapsis begins before the synaptonemal complex develops and is not completed until near the end of prophase I. Crossover usually occurs when matching regions on matching chromosomes break and then reconnect to the other chromosome. Crossing over was described
16952923
Prophase


at the completion of synapsis. Chromatin has condensed enough that chromosomes can now be resolved in microscopy. Structures called recombination nodules form on the synaptonemal complex of bivalents. These recombination nodules facilitate genetic exchange between the non-sister chromatids of the synaptonemal complex in an event known as crossing-over or genetic recombination. Multiple recombination events can occur on each bivalent. In humans, an average of 2-3 events occur on each chromosome. In the fourth phase of prophase I, diplotene (from the Greek for “twofold”
15175170
Genetic recombination


During meiosis in eukaryotes, genetic recombination involves the pairing of homologous chromosomes. This may be followed by information transfer between the chromosomes. The information transfer may occur without physical exchange (a section of genetic material is copied from one chromosome to another, without the donating chromosome being changed) (see SDSA pathway in Figure); or by the breaking and rejoining of DNA strands, which forms new molecules of DNA (see DHJ pathway in Figure). Recombination may also occur during mitosis in eukaryotes where it ordinarily involves the two
331657
Neurospora crassa


other fungi (reviewed by Whitehouse), led to an extensive characterization of gene conversion. It became clear from this work that gene conversion events arise when a molecular recombination event happens to occur near the genetic markers under study (e.g. "pan-2" mutations in the above example). Thus studies of gene conversion allowed insight into the details of the molecular mechanism of recombination. Over the decades since the original observations of Mary Mitchell in 1955, a sequence of molecular models of recombination have been proposed based on both emerging genetic data
15616975
History of botany


material that occurs in the germ cells. In the 1920s and 1930s population genetics combined the theory of evolution with Mendelian genetics to produce the modern synthesis. By the mid-1960s the molecular basis of metabolism and reproduction was firmly established through the new discipline of molecular biology. Genetic engineering, the insertion of genes into a host cell for cloning, began in the 1970s with the invention of recombinant DNA techniques and its commercial applications applied to agricultural crops followed in the 1990s. There was now the potential to identify organisms by molecular "fingerprinting
4455557
FLP-FRT recombination


) was transfected into mammalian cell culture, and recombination in mammalian cells was confirmed. This variant of FLP only has 4 amino acid substitutions: P2S, L33S, Y108N, and S294P. Genetic mosaicism occurs within an organism when similar cell types express different phenotypes due to dissimilar genotypes at specific loci. Simply put, this occurs when one organism contains different genotypes, which is usually rare in nature. However, this can be easily (and problematically) produced using FLP-FRT recombination. If two different FRT sites are present within
18087322
Genetic recombination


In eukaryotes, recombination during meiosis is facilitated by chromosomal crossover. The crossover process leads to offspring having different combinations of genes from those of their parents, and can occasionally produce new chimeric alleles. The shuffling of genes brought about by genetic recombination produces increased genetic variation. It also allows sexually reproducing organisms to avoid Muller's ratchet, in which the genomes of an asexual population accumulate genetic deletions in an irreversible manner. Chromosomal crossover involves recombination between the paired chromosomes inherited from each of one's parents, generally occurring during meiosis.
331661
Genome evolution


shuffling is a mechanism by which new genes are created. This can occur when two or more exons from different genes are combined together or when exons are duplicated. Exon shuffling results in new genes by altering the current intron-exon structure. This can occur by any of the following processes: transposon mediated shuffling, sexual recombination or non-homologous recombination (also called illegitimate recombination). Exon shuffling may introduce new genes into the genome that can be either selected against and deleted or selectively favored and conserved. Many species exhibit
12490477
Tag SNP


from different chromosomes can jointly confer an evolutionarily selected phenotype or can affect the viability of potential offspring. In families LD is highest because of the lowest numbers of recombination events (fewest meiosis events). This is especially true between inbred lines. In populations LD exists because of selection, physical closeness of the genes that causes low recombination rates or due to recent crossing or migration. On a population level, processes that influence linkage disequilibrium include genetic linkage, epistatic natural selection, rate of recombination, mutation, genetic drift, random
17559843
Ectopic recombination


recombination is roughly on par with that of allelic (or traditional) recombination. If the alleles at two loci are heterozygous, then ectopic recombination is relatively likely to occur, whereas if the alleles are homozygous, they will almost certainly undergo allelic recombination. Ectopic recombination does not require loci involved to be close to one another; it can occur between loci that are widely separated on a single chromosome, and has even been known to occur across chromosomes. Neither does it require high levels of homology between sequences—the lower limit
4528439
Chromosomal crossover


, it is theoretically possible to have any combination of parental alleles in an offspring, and the fact that two alleles appear together in one offspring does not have any influence on the statistical probability that another offspring will have the same combination. This principle of "independent assortment" of genes is fundamental to genetic inheritance. However, the frequency of recombination is actually not the same for all gene combinations. This leads to the notion of "genetic distance", which is a measure of recombination frequency averaged over a (suitably large
16952938
Molecular evolution


The formation of novel genes from scratch typically can not occur within genomic regions of high gene density. The essential events for de novo formation of genes is recombination/mutation which includes insertions, deletions, and inversions. These events are tolerated if the consequence of these genetic events does not interfere in cellular activities. Most genomes comprise prophages wherein genetic modifications do not, in general, affect the host genome propagation. Hence, there is higher probability of genetic modifications, in regions such as prophages, which is proportional to the probability
10090486
Genetic recombination


. Gene conversion events can be distinguished as deviations in an individual meiosis from the normal 2:2 segregation pattern (e.g. a 3:1 pattern). Recombination can occur between DNA sequences that contain no sequence homology. This can cause chromosomal translocations, sometimes leading to cancer. B cells of the immune system perform genetic recombination, called immunoglobulin class switching. It is a biological mechanism that changes an antibody from one class to another, for example, from an isotype called IgM to an isotype called IgG. In genetic engineering, recombination can also refer
331666
Fitness proportionate selection


Fitness proportionate selection, also known as roulette wheel selection, is a genetic operator used in genetic algorithms for selecting potentially useful solutions for recombination. In fitness proportionate selection, as in all selection methods, the fitness function assigns a fitness to possible solutions or chromosomes. This fitness level is used to associate a probability of selection with each individual chromosome. If formula_1 is the fitness of individual formula_2 in the population, its probability of being selected is where formula_4 is the number of individuals in the population. This could be imagined similar
7804541
Non-allelic homologous recombination


Non-allelic homologous recombination (NAHR) is a form of homologous recombination that occurs between two lengths of DNA that have high sequence similarity, but are not alleles. It usually occurs between sequences of DNA that have been previously duplicated through evolution, and therefore have low copy repeats (LCRs). These repeat elements typically range from 10–300 kb in length and share 95-97% sequence identity. During meiosis or mitosis, LCRs can misalign and subsequent crossing-over can result in genetic rearrangement. When non-allelic homologous
6553607
Barbara McClintock


and Creighton proved the link between chromosomal crossover during meiosis and the recombination of genetic traits. They observed how the recombination of chromosomes seen under a microscope correlated with new traits. Until this point, it had only been hypothesized that genetic recombination could occur during meiosis, although it had not been shown genetically. McClintock published the first genetic map for maize in 1931, showing the order of three genes on maize chromosome 9. This information provided necessary data for the crossing-over study she published with Creighton; they also showed that
10524479
Genetically modified mouse


Smithies and Mario Capecchi, involves modifying embryonic stem cells with a DNA construct containing DNA sequences homologous to the target gene. Embryonic stem cells that recombine with the genomic DNA are selected for and they are then injected into the mice blastocysts. This method is used to manipulate a single gene, in most cases "knocking out" the target gene, although increasingly more subtle and complex genetic manipulation can occur (e.g. humanisation of a specific protein, or only changing single nucleotides). Genetically modified mice are used extensively in research as
4648795
Genetic operator


. By recombining portions of good solutions, the genetic algorithm is more likely to create a better solution. As with selection, there are a number of different methods for combining the parent solutions, including the "edge recombination operator" (ERO) and the 'cut and splice crossover' and 'uniform crossover' methods. The crossover method is often chosen to closely match the chromosome's representation of the solution; this may become particularly important when variables are grouped together as building blocks, which might be disrupted by a non
7804575
Genetically modified organism


breeding or artificial selection (as contrasted with natural selection). The process of selective breeding, in which organisms with desired traits (and thus with the desired genes) are used to breed the next generation and organisms lacking the trait are not bred, is a precursor to the modern concept of genetic modification. Various advancements in genetics allowed humans to directly alter the DNA and therefore genes of organisms. In 1972 Paul Berg created the first recombinant DNA molecule when he combined DNA from a monkey virus with that of the lambda virus
12021490
Human genetic variation


show that each human has on average 60 new mutations compared to their parents. Causes of differences between individuals include independent assortment, the exchange of genes (crossing over and recombination) during reproduction (through meiosis) and various mutational events. There are at least three reasons why genetic variation exists between populations. Natural selection may confer an adaptive advantage to individuals in a specific environment if an allele provides a competitive advantage. Alleles under selection are likely to occur only in those geographic regions where they confer an advantage. A second important
8820597
Founder effect


its mutation has the potential to express the founder effect, for instance a goat or a human. Founder mutations originate in long stretches of DNA on a single chromosome; indeed, the original haplotype is the whole chromosome. As the generations progress, the proportion of the haplotype that is common to all carriers of the mutation is shortened (due to genetic recombination). This shortening allows scientists to roughly estimate the age of the mutation. The founder effect is a special case of genetic drift, occurring when a small group in
13255954
Genetic load


's ratchet, and occurs in the absence of beneficial mutations, when after the most-fit genotype has been lost, it cannot be regained by genetic recombination. Deterministic accumulation of mutation load occurs in asexuals when the deleterious mutation rate exceeds one per replication. Sexually reproducing species are expected to have lower genetic loads. This is one hypothesis for the evolutionary advantage of sexual reproduction. Purging of deleterious mutations in sexual populations is facilitated by synergistic epistasis among deleterious mutations. High load can lead to a small population size, which
8742013
Centimorgan


odd number of chromosomal crossovers between the two markers, the distance in centimorgans does not correspond exactly to the probability of genetic recombination. Assuming Haldane's map function, in which the number of chromosomal crossovers is distributed according to a Poisson distribution, a genetic distance of "d" centimorgans will lead to an odd number of chromosomal crossovers, and hence a detectable genetic recombination, with probability where sinh is the hyperbolic sine function. The probability of recombination is approximately "d"/100 for small values of "d" and approaches 50%
8610312
Inbreeding depression


recessive individual is likely to eliminate itself, naturally limiting the expression of its phenotype. Third, recessive deleterious alleles will be "masked" by heterozygosity, and so in a dominant-recessive trait, heterozygotes will not be selected against. When recessive deleterious alleles occur in the heterozygous state, where their potentially deleterious expression is masked by the corresponding wild-type allele, this masking phenomenon is referred to as complementation (see complementation (genetics)). In general, sexual reproduction in eukaryotes has two fundamental aspects: recombination during
6204630
Natural selection


variation. As a result, the genetic variation at those sites is higher than at sites where variation does influence fitness. However, after a period with no new mutations, the genetic variation at these sites is eliminated due to genetic drift. Natural selection reduces genetic variation by eliminating maladapted individuals, and consequently the mutations that caused the maladaptation. At the same time, new mutations occur, resulting in a mutation–selection balance. The exact outcome of the two processes depends both on the rate at which new mutations occur and
1233560
Heteroplasmy


in cells, and may depend on tissue type, age, and genetic distance. Selective differences between naturally occurring mtDNA types may pose challenges for gene therapies. In mitochondrial DNA, there is evidence for potent germline purifying selection, as well as purifying selection during embryogenesis. Additionally, there is a dose-dependent decrease in reproduction ability for females that have mutations in mitochondrial DNA. This demonstrates another selection mechanism to prevent the evolutionary preservation of harmful mutations. It is very rare for organelle genes from different lineages to recombine. These
21229167
DMC1 (gene)


and protein were discovered in the budding yeast S. cerevisiae by Douglas Bishop when he was a postdoctoral fellow in the laboratory of Nancy Kleckner at Harvard University. The protein encoded by this gene is essential for meiotic homologous recombination. Genetic recombination in meiosis plays an important role in generating diversity of genetic information and facilitates the reductional segregation of chromosomes that must occur for formation of gametes during sexual reproduction. Like other members of the Rad51/RecA family, Dmc1 stabilizes strand exchange intermediates (Rad1/RecA-stretched DNA, or RS-
378001
Site-specific recombination


pathogenesis, and movement of mobile genetic elements (Nash 1996). For the same reasons, they present a potential basis for the development of genetic engineering tools. Recombination sites are typically between 30 and 200 nucleotides in length and consist of two motifs with a partial inverted-repeat symmetry, to which the recombinase binds, and which flank a central crossover sequence at which the recombination takes place. The pairs of sites between which the recombination occurs are usually identical, but there are exceptions (e.g. attP and attB of λ integrase
14345306
Chromosome segregation


process of alignment of paired homologous chromosomes is called synapsis (see Synapsis). During synapsis, genetic recombination usually occurs. Some of the recombination events occur by crossing over (involving physical exchange between two chromatids), but most recombination events involve information exchange but not physical exchange between two chromatids (see Synthesis-dependent strand annealing (SDSA)). Following recombination, chromosome segregation occurs as indicated by the stages metaphase I and anaphase I in the meiosis diagram. Different pairs of chromosomes segregate independently of each other, a process
17429897
RecLOH


RecLOH is a term in genetics that is an abbreviation for "Recombinant Loss of Heterozygosity". This is a type of mutation which occurs with DNA by recombination. From a pair of equivalent ("homologous"), but slightly different (heterozygous) genes, a pair of identical genes results. In this case there is a non-reciprocal exchange of genetic code between the chromosomes, in contrast to chromosomal crossover, because genetic information is lost. In genetic genealogy, the term is used particularly concerning similar seeming events in
3228518
Agelena consociata


A. consociata and is only successful when many individuals participate. When only a few individuals attempt to disperse, they are frequently subjects of predation. While voluntary dispersion may not often occur, animal dispersion occasionally does, as dispersion over large distances is likely to be passive transport by bats or other vertebrates. Passive animal dispersion may occur often enough that selection has not favored active dispersion. Limited dispersion, however, can be consequential. The spider could be more susceptible to a single parasite or a natural disaster since they are all genetically
19832253
Utricularia gibba


to have occurred via both numerous microdeletions and some large-scale recombinant deletions. It is hypothesized that a "sloppy" recombination process has caused unused material to be deleted over time. The presence of numerous GC-rich sequences throughout the nuclear genome of "U. gibba" is considered to have created a molecular mechanistic bias in favor of deletions, but this does not preclude the presence of a selection pressure to preserve such deletions. Selection pressures in favor of conserving energy or conserving phosphorus have been suggested to be operative in the
16867128
Holland's schema theorem


a string belonging to the schema formula_5 will be created "from scratch" by mutation of a single string (or recombination of two strings) that did "not" belong to formula_5 in the previous generation. The schema theorem holds under the assumption of a genetic algorithm that maintains an infinitely large population, but does not always carry over to (finite) practice: due to sampling error in the initial population, genetic algorithms may converge on schemata that have no selective advantage. This happens in particular in multimodal optimization, where
5617536
Virus


". Genetic recombination is the process by which a strand of DNA is broken and then joined to the end of a different DNA molecule. This can occur when viruses infect cells simultaneously and studies of viral evolution have shown that recombination has been rampant in the species studied. Recombination is common to both RNA and DNA viruses. Viral populations do not grow through cell division, because they are acellular. Instead, they use the machinery and metabolism of a host cell to produce multiple copies of themselves, and they "assemble"
5611923
Homologous recombination


Homologous recombination is a type of genetic recombination in which nucleotide sequences are exchanged between two similar or identical molecules of DNA. It is most widely used by cells to accurately repair harmful breaks that occur on both strands of DNA, known as double-strand breaks (DSB). Homologous recombination also produces new combinations of DNA sequences during meiosis, the process by which eukaryotes make gamete cells, like sperm and egg cells in animals. These new combinations of DNA represent genetic variation in offspring, which in turn enables populations to adapt
10077888
Drosophila neotestacea


duplication of an importin gene, a type of nuclear transport protein. Often, selfish X chromosomes suppress genetic recombination during meiosis. This process maintains the gene clusters that promote X chromosome drive, but also can lead to an accumulation of deleterious mutations via a process known as Muller's ratchet. The "D. neotestacea" selfish X suppresses recombination in lab settings, but occasional recombination occurs in the wild evidenced by recombinant genetic regions in wild-caught flies. Other Testacea species harbour selfish X chromosomes, raising the question of whether X
21750494
Inbreeding


alleles most likely occurs through Muller's ratchet, when an asexual population's genome accumulates deleterious mutations that are irreversible. Despite all its disadvantages, inbreeding can also have a variety of advantages, such as reducing the recombination load, and allowing the expression of recessive advantageous phenotypes. It has been proposed that under circumstances when the advantages of inbreeding outweigh the disadvantages, preferential breeding within small groups could be promoted, potentially leading to speciation. Autosomal recessive disorders occur in individuals who have two copies of an allele for a particular recessive genetic
10212957
V(D)J recombination


V(D)J recombination is the unique mechanism of genetic recombination that occurs only in developing lymphocytes during the early stages of T and B cell maturation. It involves somatic recombination, and results in the highly diverse repertoire of antibodies/immunoglobulins (Igs) and T cell receptors (TCRs) found on B cells and T cells, respectively. The process is a defining feature of the adaptive immune system. V(D)J recombination occurs in the primary lymphoid organs (bone marrow for B cells and thymus for T cells) and in a nearly random fashion
4143025
HIV superinfection


HIV virions each contain a double-stranded RNA genome. When superinfection occurs, cells contain 2 different HIV strains. These can exchange genetic material such that an RNA strand from each strain is contained in a single virion. As this progeny virion infects new cells, the RNA template transcribed by viral reverse transcriptase changes, resulting in a reverse transcript with genetic material from both parental viruses. Recombination results in a rapid increase in HIV viral diversity, causing quicker adaptations to host immune response and resistance to ART. Recombination tends to produce
2454243
Protein engineering


directed evolution, random mutagenesis, e.g. by error-prone PCR or sequence saturation mutagenesis, is applied to a protein, and a selection regime is used to select variants having desired traits. Further rounds of mutation and selection are then applied. This method mimics natural evolution and, in general, produces superior results to rational design. An added process, termed DNA shuffling, mixes and matches pieces of successful variants to produce better results. Such processes mimic the recombination that occurs naturally during sexual reproduction. Advantages of directed evolution are
2963227
Mosaic (genetics)


the exchange takes place. A phenotypic character called "twin spot" seen in "Drosophila" is a result of mitotic recombination. However, it also depends on the allelic status of the genes undergoing recombination. Twin spot occurs only if the heterozygous genes are linked in repulsion, i.e. the trans phase. The recombination needs to occur between the centromeres of the adjacent gene. This gives an appearance of yellow patches on the wild-type background in "Drosophila". another example of mitotic recombination is the Bloom's syndrome,
19616990
Artificial intelligence


the guesses) and then allow them to mutate and recombine, selecting only the fittest to survive each generation (refining the guesses). Classic evolutionary algorithms include genetic algorithms, gene expression programming, and genetic programming. Alternatively, distributed search processes can coordinate via swarm intelligence algorithms. Two popular swarm algorithms used in search are particle swarm optimization (inspired by bird flocking) and ant colony optimization (inspired by ant trails). Logic is used for knowledge representation and problem solving, but it can be applied to other problems as
543639
Genetic recombination


risk of cancer (see DNA repair-deficiency disorder). In bacteria, transformation is a process of gene transfer that ordinarily occurs between individual cells of the same bacterial species. Transformation involves integration of donor DNA into the recipient chromosome by recombination. This process appears to be an adaptation for repairing DNA damages in the recipient chromosome by HRR. Transformation may provide a benefit to pathogenic bacteria by allowing repair of DNA damage, particularly damages that occur in the inflammatory, oxidizing environment associated with infection of a host. When two or
331669
Washington Initiative 522 (2012)


taxonomic family, in a way that does not occur by natural multiplication or natural recombination." Section three requires that "any food offered for retail sale" be labeled "clearly and conspicuously" if it contains genetically-engineered ingredients, with certain exceptions. Exemptions consistent with current federal regulations include prepared foods such as those coming from a restaurant, meat from animals fed genetically engineered feeds, alcoholic beverages and foods processed with GE enzymes. For non-exempt foods, it would require "on the front of the package"
12323994
Evolution of sexual reproduction


alone does not account for the ubiquity of sex. Otto and Gerstein further stated that “it seems doubtful to us that strong selection per gene is sufficiently commonplace for the Red Queen hypothesis to explain the ubiquity of sex.” Parker reviewed numerous genetic studies on plant disease resistance and failed to uncover a single example consistent with the assumptions of the Red Queen hypothesis. As discussed in the earlier part of this article, sexual reproduction is conventionally explained as an adaptation for producing genetic variation through allelic recombination. As acknowledged above, however
7898849
Genetic engineering


introduced directly into the host organism or into a cell that is then fused or hybridised with the host. This relies on recombinant nucleic acid techniques to form new combinations of heritable genetic material followed by the incorporation of that material either indirectly through a vector system or directly through micro-injection, macro-injection or micro-encapsulation. Genetic engineering does not normally include traditional breeding, in vitro fertilisation, induction of polyploidy, mutagenesis and cell fusion techniques that do not use recombinant nucleic acids or a genetically modified organism in the process
12021917
Lamarckism


. The hologenome can vary like any other genome by mutation, sexual recombination, and chromosome rearrangement, but in addition it can vary when populations of microorganisms increase or decrease (resembling Lamarckian use and disuse), and when it gains new kinds of microorganism (resembling Lamarckian inheritance of acquired characteristics). These changes are then passed on to offspring. The mechanism is largely uncontroversial, and natural selection does sometimes occur at whole system (hologenome) level, but it is not clear that this is always the case. The Baldwin
15893831
Homologous chromosome


it takes more time for the chromatin to replicate and for the homologous chromosomes to be properly oriented and segregated by the processes of pairing and synapsis in meiosis I. During meiosis, genetic recombination (by random segregation) and crossing over produces daughter cells that each contain different combinations of maternally and paternally coded genes. This recombination of genes allows for the introduction of new allele pairings and genetic variation. Genetic variation among organisms helps make a population more stable by providing a wider range of genetic traits for natural selection to act on. In
12126230
Optimal foraging theory


such as the ones cited in the examples above, provide quantitative support for optimal foraging theory and demonstrate its usefulness, the model has received criticism regarding its validity and limitations. First, optimal foraging theory relies on the assumption that natural selection will optimize foraging strategies of organisms. However, natural selection is not an all-powerful force that produces perfect designs, but rather a passive process of selection for genetically-based traits that increase organisms' reproductive success. Given that genetics involves interactions between loci, recombination, and other complexities
9006000
Linkage disequilibrium


In population genetics, linkage disequilibrium is the non-random association of alleles at different loci in a given population. Loci are said to be in linkage disequilibrium when the frequency of association of their different alleles is higher or lower than what would be expected if the loci were independent and associated randomly. Linkage disequilibrium is influenced by many factors, including selection, the rate of genetic recombination, mutation rate, genetic drift, the system of mating, population structure, and genetic linkage. As a result, the pattern of linkage
11107846
Antigenic variation


as their RNA counterparts. Antigenic variation within viruses can be categories into 6 different categories called antigenic drift, shift, rift lift, sift, and gift Antigenic rift: Recombination of viral gene. This again occurs when there are again two viral cells that infect the same host cell. In this instance through the viruses recombine with pieces of each gene creating a new gene instead of simply switching out genes. Recombination has been extensively studied in avian influenza strains as to how the genetics of H5N1 have changed over time. Antigenic drift
15041811
Cernunnos deficiency


homologous end-joining factor 1" gene. NHEJ1 encodes a protein which helps repair of breaks in double-stranded DNA. It might additionally act as a connection between XRCC4 and other NHEJ factors(at DNA ends) When a mutation occurs in NHEJ1, then one sees that nucleotide deletions cause "V(D)J recombination", signal joints, to be affected. V(D)J recombination is a genetic recombination that happens in early stages of B and T cell maturation. The diagnosis of Cernunnos deficiency will find the following in an affected individual via clinical features
6406578
Adaptive mutation


for several days. The degree to which revertants were observed in yeast was not as high as with bacteria. Other scientists have conducted similar experiments, such as Hall who tested histidine revertants, or Steele & Jinks-Robertson who tested lysine. These experiments demonstrate how recombination and DNA replication are necessary for adaptive mutation. However, in lysine-tested cells, recombination continued to occur even without selection for it. Steele and Jinks-Robertson concluded that recombination occurred in all circumstances, adaptive or otherwise, while mutations were present only
10038552
Karyogamy


a zygospore, which can then enter meiosis, a process of chromosome duplication, recombination, and cell division, to create four new haploid gamete cells. One possible advantage of sexual reproduction is that it results in more genetic variability, providing the opportunity for adaptation through natural selection. Another advantage is efficient recombinational repair of DNA damages during meiosis. Thus, karyogamy is the key step in bringing together a variety of genetic material in order to ensure recombination in meiosis. The Amoebozoa is a large group of mostly single-celled species
18806600
Balancer chromosome


Balancer chromosomes are special, modified chromosomes used for genetically screening a population of organisms to select for heterozygotes. Balancer chromosomes can be used as a genetic tool to prevent crossing over (genetic recombination) between homologous chromosomes during meiosis. Balancers are most often used in "Drosophila melanogaster" (fruit fly) genetics to allow populations of flies carrying heterozygous mutations to be maintained without constantly screening for the mutations but can also be used in mice. Balancer chromosomes have three important properties: they suppress recombination with their homologs, carry dominant markers
12166308
Smith–Lemli–Opitz syndrome


because they survive longer than genetic models. For example, one study examined the retinal degeneration of SLOS, which in rats does not occur until at least one month after birth. Genetic models of SLOS are created by knocking out the "DHCR7" gene. One study used homologous recombination to disrupt "DCHR7" in mouse embryonic stem cells. Similar to what is found in humans, heterozygous mice (having only one mutated allele) were phentoypically normal, and were crossed to produce pups (young mice) homozygous for the mutated
10282798
Evolution of sexual reproduction


main hypotheses which explain how sex may act to remove deleterious genes from the genome. While DNA is able to recombine to modify alleles, DNA is also susceptible to mutations within the sequence that can affect an organism in a negative manner. Asexual organisms do not have the ability to recombine their genetic information to form new and differing alleles. Once a mutation occurs in the DNA or other genetic carrying sequence, there is no way for the mutation to be removed from the population until another mutation occurs that ultimately deletes the primary mutation
7898857
Genetic recombination


sister chromosomes formed after chromosomal replication. In this case, new combinations of alleles are not produced since the sister chromosomes are usually identical. In meiosis and mitosis, recombination occurs between similar molecules of DNA (homologous sequences). In meiosis, non-sister homologous chromosomes pair with each other so that recombination characteristically occurs between non-sister homologues. In both meiotic and mitotic cells, recombination between homologous chromosomes is a common mechanism used in DNA repair. Gene conversion - the process during which homologous sequences are made identical also falls
331658
Natural selection


kin selection and the evolution of reciprocal altruism. A portion of all genetic variation is functionally neutral, producing no phenotypic effect or significant difference in fitness. Motoo Kimura's neutral theory of molecular evolution by genetic drift proposes that this variation accounts for a large fraction of observed genetic diversity. Neutral events can radically reduce genetic variation through population bottlenecks. which among other things can cause the founder effect in initially small new populations. When genetic variation does not result in differences in fitness, selection cannot directly affect the frequency of such
1233559
Homologous recombination


occur in somatic cells like white blood cells and skin cells that divide through mitosis. In 1947, the microbiologist Joshua Lederberg showed that bacteria—which had been assumed to reproduce only asexually through binary fission—are capable of genetic recombination, which is more similar to sexual reproduction. This work established "E. coli" as a model organism in genetics, and helped Lederberg win the 1958 Nobel Prize in Physiology or Medicine. Building on studies in fungi, in 1964 Robin Holliday proposed a model for recombination in meiosis which introduced key
10077895
Genetic recombination


During prophase I (pachytene stage) the four available chromatids are in tight formation with one another. While in this formation, homologous sites on two chromatids can closely pair with one another, and may exchange genetic information. Because recombination can occur with small probability at any location along chromosome, the frequency of recombination between two locations depends on the distance separating them. Therefore, for genes sufficiently distant on the same chromosome, the amount of crossover is high enough to destroy the correlation between alleles. Tracking the movement of genes resulting
331662
Saccharomyces cerevisiae


idea that production of genetic variation is the main selective force maintaining meiosis in this organism. However, this finding is consistent with the alternative idea that the main selective force maintaining meiosis is enhanced recombinational repair of DNA damage, since this benefit is realized during each meiosis, whether or not out-crossing occurs. "S. cerevisiae" was the first eukaryotic genome to be completely sequenced. The genome sequence was released to the public domain on April 24, 1996. Since then, regular updates have been maintained at the Saccharomyces Genome
9431288
Genetic drift


but it is not clear how this is related to the actual number of individuals in a population. Genetic linkage to other genes that are under selection can reduce the effective population size experienced by a neutral allele. With a higher recombination rate, linkage decreases and with it this local effect on effective population size. This effect is visible in molecular data as a correlation between local recombination rate and genetic diversity, and negative correlation between gene density and diversity at noncoding DNA regions. Stochasticity associated with linkage to other genes that are under
21220414
Genetic linkage


recombination compared to males. It is theorised that there are unique selections acting or meiotic drivers which influence the difference in rates. The difference in rates may also reflect the vastly different environments and conditions of meiosis in oogenesis and spermatogenesis. With very large pedigrees or with very dense genetic marker data, such as from whole-genome sequencing, it is possible to precisely locate recombinations. With this type of genetic analysis, a meiosis indicator is assigned to each position of the genome for each meiosis in a pedigree. The indicator indicates
892035