Question

A large family has a history of multiple aneuploid diseases such as Down Syndrome, trisomy-18 and Klinefelter Syndrome (XXY). The propensity to defects seems to be inherited, but the gene responsible is unknown. What types of candidate genes would be most likely to lead to aneuploidy if they were mutated?

Answer 1

Answer:

Genes coding for proteins involved in chiasma formation.

Explanation:

Chiasma is the connecting link between two non sister chromatids from homologous chromosomes. At chiasma chromosomal crossover takes place in which the genetic material is exchanged between the chromatids. During meiosis aneuploidy occurs if chiasma is absent or impaired due to a mutation in genes encoding for proteins involved in chiasma formation.

Aneuploidy is characterised by presence of abnormal number of chromosomes in cells. They can be 45 or 47 in number apart from the usual 46. Due to impaired chiasma, chromosome pair fails to separate and is passed on to the egg or sperm as it is hence there is one gamete with an extra chromosome and one gamete with a less chromosome. Aneuploidy can result in many genetic disorders like three copies of chromosome 21 can result in Down syndrome.