Meiosis is the process of dividing cells in humans. In meiosis, the chromosome pairs splits 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<unk> , 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. It explains why even identical twins are not genetically 100% identical. The second random process can give rise to genetic mistakes. In the deletion and<unk>  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 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, there is the 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, sports or science. In negative cases, you have to deal with a syndrome or a severe disability, as in this case the<unk> . Based on the meiotic process, the syndrome may occur in two ways. * 1. 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. * 2. a parent is unknowingly carrier of a chromosome with a copy number variation and passes it through 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 duplication syndrome
13q deletion syndrome
2q37 deletion syndrome
1q21.1 deletion syndrome
22q11.2 duplication syndrome
22q13 deletion syndrome
Chromosome 5q deletion syndrome
22q11.2 distal deletion syndrome