Pre-implantation Two major types of pre-implantation methods can be used for social<unk> . Both of them are based on actively rendering the second sex chromosome to be either a Y chromosome (resulting in a male), or an X chromosome (resulting in a female). The Ericsson method The Ericsson method, first applied in a clinical setting in the 1970s by Dr. Ronald J. Ericsson, uses higher concentrations of sperm of the desired sex to increase the likelihood of conceiving that sex. When used to increase the likelihood of a female child, studies have resulted in between 70% and 80% female children. When used to increase the likelihood of a male child, studies have resulted in between 50% to 75% male children. Currently, approximately 50 gender<unk>  centers in the United States use the Ericsson Method for artificial gender<unk> . The Ericsson method separates male and female sperm by passing them through a column filled with blood protein, human serum albumin. As the sperms enter the human serum albumin, the differences in mass between the X and Y chromosomes manifest as the lighter male sperms push deeper into the protein than the females dragged down by the weight of the extra "leg" of the X sex chromosome. This tiny difference creates separate layers of concentrated male and female sperm. The layers of gender-selected sperm are of higher concentrations but not pure. This lack of purity explains the 30% chance of gender<unk>  failure of the Ericsson method. IVF/PGD technique An 6-celled embryo prior to IVF/PGD analysis After ovarian stimulation, multiple eggs are removed from the mother. The eggs are fertilized in the laboratory using the father's sperm in a technique called in vitro fertilization (IVF). "In vitro" is Latin for "within glass". Fertilized eggs are called embryos. As the embryos develop through mitosis, they are separated by sex. Embryos of the desired gender are implanted back in the mother's uterus. Prior to fertilization with IVF, the fertilized eggs can be genetically biopsied with preimplantation genetic diagnosis (PGD) to increase fertilization success. Once an embryo grows to a 6-8 cell size, a small laser incision in the egg membrane (zona pellucida) allows safe removal of one of the cells. Every cell in the embryo contains an identical copy of the genome of the entire person. Removal of one of these cells does not harm the developing embryo. A Geneticist then studies the chromosomes in the extracted cells for genetic defects and for a definite analysis of the embryo's gender. Embryos of the desired sex and with acceptable genetics are then placed back into the mother. The IVF/PGD technique is favored over the Ericsson method because of the stricter control of the offspring gender in the laboratory. Since only embryos of the desired sex are transferred to the mother, IVF/PGD avoids the small likelihood present in the Ericsson method of an undesired sperm fertilizing the egg. Gender<unk>  success rates for IVF/PGD are very high. The technique is recommended for couples who will not accept a child of the undesired gender. Timing methods Timing methods aim to affect the sex ratio of the resultant children by having sexual intercourse at specific times as related to ovulation. Studies have not been consistent about whether timing methods have any influence on the sex of the baby, with some showing no correlation and others showing just the opposite. *The Shettles method, first formally theorized in the 1960s by Landrum B. Shettles, proposes that sperm containing the X (female) chromosome are more resilient than sperm containing the Y (male) chromosome. The method advocates intercourse two to four days prior to ovulation. By the time ovulation occurs, the cervix should contain a higher concentration of female sperm still capable of fertilization (with most of the male sperm already dead). Intercourse close to ovulation, on the other hand, should increase the chances of conceiving a boy since the concentration of Y sperm will be higher at the height of the menstrual cycle. *The Whelan method is an "intercourse timing" method that advocates the opposite of the Shettles method. The Whelan method suggests intercourse four to six days prior to ovulation to increase the likelihood of fertilization by male sperm. Sperm sorting Sperm sorting is an advanced technique that sorts sperm "in vitro" by flow cytometry. This shines a laser at the sperm to distinguish X and Y chromosomes, and can automatically separate the sperm out into different samples. During the early to mid 1980s, Dr. Glenn Spaulding was the first to sort viable whole human and animal spermatozoa using a flow cytometer, and utilized the sorted motile rabbit sperm for artificial insemination. Subsequently, the first patent application disclosing the method to sort "two viable subpopulations enriched for x- or y- sperm" was filed in April 1987 as US Application Serial Number 35,986 and later became part of US Patent 5,021,244; and the patent included the discovery of haploid expression (sex-associated membrane proteins, or SAM proteins) and the development of monoclonal antibodies to those proteins. Additional applications and methods were added, including antibodies, from 1987 through 1997. At the time of the patent filing, both Lawrence Livermore National Laboratories and the USDA were only sorting fixed sperm nuclei, after the Application Serial Number 35,986 patent filing a new technique was utilized by the USDA where "sperm were briefly sonicated to remove tails". USDA in conjunction with Lawrence Livermore National Laboratories, 'Beltsfield Sperm Sexing Technology' relies on the DNA difference between the X- and Y- chromosomes. Prior to flow cytometric sorting, semen is labeled with a fluorescent dye called Hoechst 33342 which binds to the DNA of each spermatozoon. As the X chromosome is larger (i.e. has more DNA) than the Y chromosome, the "female" (X-chromosome bearing) spermatozoa will absorb a greater amount of dye than its male (Y-chromosome bearing) counterpart. As a consequence, when exposed to UV light during flow cytometry, X spermatozoa fluoresce brighter than Y- spermatozoa. As the spermatozoa pass through the flow cytometer in single file, each spermatozoon is encased by a single droplet of fluid and assigned an electric charge corresponding to its chromosome status (e.g. X-positive charge, Y-negative charge). The stream of X- and Y- droplets is then separated by means of electrostatic deflection and collected into separate collection tubes for subsequent processing. The technology is already in commercial use for animal farming. It is currently being trialed on humans in the US under the trademark MicroSort; it claims a 90% success rate but is still considered experimental by the FDA. Post-implantation<unk>  after implantation can be performed by prenatal sex discernment, followed by sex-selective abortion of any offspring of the unwanted sex. For prenatal sex discernment, a blood test can be taken from the mother for testing of small amounts of fetal DNA within it, and has been estimated to be reliable more than 98% of the time, as long as the samples are taken after the seventh week of pregnancy. Post-birth Sex-selective infanticide - Killing children of the unwanted sex. Though illegal in most parts of the world, it is still practiced. Sex-selective child abandonment - Abandoning children of the unwanted sex. Though illegal in most parts of the world, it is still practiced. Sex-selective adoption - Placing children of the unwanted sex up for adoption. Less commonly viewed as a method of social<unk> , adoption affords families that have a gender preference a legal means of choosing offspring of a particular sex.
Sex selection
Cancer selection
Structural inheritance
Sexual reproduction
Dynamic mutation
Nuclear sexing
Immune privilege
Genomic imprinting