Question

Suppose that a carrier of familial Down syndrome mated with a person with a normal karyotype. Which gamete from the carrier parent could fuse with a gamete from the normal parent to produce a trisomy-21 zygote

Answer 1

Explanation:

Chromosomal mutations, non-point mutations or chromosomopathies are alterations in the number of genes or in the order of these within the chromosomes. They are due to errors during gametogenesis (formation of gametes by meiosis) or the first divisions of the zygote. In the first case, the anomaly will be present in all the individual's cell lines, while when the anomaly occurs in the zygote it can lead to mosaicism, thus coexisting normal cell populations with others that present chromosomal mutations.

Karyotype of human female cell in metaphase state.

These alterations can be observed during the metaphase of the cell cycle and that have their origin in breaks (clastogenic processes) of unrepaired or poorly repaired DNA chains, among other factors.

Currently, there is extensive knowledge of the human karyotype and chromosomal abnormalities. Since these alterations are genetic abnormalities, they can be transmitted to the offspring in case they affect the germ cells. It is estimated that about 60% of abortions in the first trimester of pregnancy are due to chromosomal abnormalities and 0.5% of newborns have aneuploidies. For this reason, the study of these mutations by means of a karyotype or an FISH is very useful to detect any anomaly in advance.