Meiosis is the process of dividing cells in humans. In meiosis, the chromosome pairs split and a representative of each pair goes to one daughter cell. In this way the number of chromosomes will be halved in each cell, while all the parts on the chromosome (genes) remain, after being randomized. Which information of the parent cell ends up in the daughter cell is purely decided by chance. Besides this random process, there is a second random process. In this second random process the DNA will be scrambled in a way that pieces are omitted (deletion), added (duplication), moved from one place to another (translocation) and inverted (inversion). This is a common process, which leads to about 0.4% variation in the DNA. A problem of the second random process is that genetic mistakes can occur. Because of the deletion and duplication process, the chromosomes that come together in a new cell may be shorter or longer. The result of this spontaneous change in the structure of DNA is a so-called copy number variation. Due to the copy number variation chromosomes of different sizes can be combined in a new cell. If this occurs around conception, the result will be a first cell of a human with a genetic variation. This can be either positive or negative. In positive cases this new human will be capable of a special skill that is assessed positively, for example, in sports or science. In negative cases, you have to deal with a<unk>  or a severe disability, as in this case the<unk> . Based on the meiotic process, the<unk>  may occur in two ways. # a spontaneous deviation (a 'de novo' situation): two chromosomes come together of which one has a copy number variation as a result of the meiosis process. # a parent is unknowingly the carrier of a chromosome with a copy number variation and passes it at conception to the child, with different consequences for the child. Due to this genetic misprint, the embryo may experience problems in the development during the first months of pregnancy. Approximately 20 to 40 days after fertilization, something goes wrong in the construction of the body parts and brain, which leads to a chain reaction.
1q21.1 deletion syndrome
13q deletion syndrome
22q13 deletion syndrome
2q37 deletion syndrome
22q11.2 distal deletion syndrome
9q34 deletion syndrome
1p36 deletion syndrome
Chromosome 5q deletion syndrome