Sometimes, during the first meiotic division, one or more of the chromosome pairs may fail to separate when the cell divides. During the second meiotic division, one or more of the chromatids may fail to separate. This is known as non-disjunction. They result in one of the daughter cells receiving an extra chromosome and the other daughter cell lacing that chromosome. This causes changes in the characteristics in the offspring. These changes to the chromosome number cause severe and distinct birth defects.
Trisomy: a condition in which an individual inherits an extra copy of a chromosomes
Trisomy: a condition in which an individual inherits an extra copy of a chromosomes
- Eg. Trisomy 21 à down-syndrome