Question

What caused the chromosomal alteration in the number 21 chromosomes? (LS3.2) A. Part of one chromosome attached to another chromosome B. Some of the genes on a chromosome were reversed C. A duplicated chromosome failed to separate during meiosis D. A part of a chromosome was lost

Answer 1

A duplicated chromosome failed to separate (nondisjunction)

Step-by-step explanation:

If nondisjunction occurs during meiosis I, homologous chromosomes fail to separate. This produces abnormal gametes that contain two members of the affected chromosome or none. This is why there is an extra chromosome in the 21 chromosomes.

Answer 2

The correct answr is - A. Part of one chromosome attached to another chromosome.

Step-by-step explanation:

Translocation is one of the chromosome abnormality that cause change in the number of the chromosome. In the translocation a part of the chromosome breaks off and bind or attached to the another chromosome.

The translocation cause various disorderes in individual one of them is Down syndrome which is the result of the alteration of chromosome number 21. In this translocation or specicifically the chromosome portion of chroromosme 14 breaks off and reattaches to the chromosome 21 result in one normal 14 and two normal 21 chromosme so there is trisomy occurs.