The Process of Meiosis and Its Relationship to Chromosome 21

01

02

In the first stage of meiosis, the chromosomes make copies of themselves; the chromosomes first line up in the center and the pairs of chromosome separate, which results in two cells with 23 chromosomes (with chromatids).

When the chromosomes lines up once again in the center to separate, chromosome 21 does not completely separate. If this happens to the egg, then it is an extra chromosome (chromosome 21) that results from this particular process.

Both the sperm and the egg cell must be “perfect” (when the egg cell contains 23 chromosomes) or they will not be able to produce a “perfect” baby.