Question

In a balanced reciprocal translocation in which two chromosomes exchange pieces, a breakpoint in which one of the following would be most likely to cause gene disruption and thus an abnormal phenotype?

(A) Giemsa negative G-band
(B) Giemsa positive G-band
(C) Giemsa negative R-band
(D) C-band

Answer 1

A breakpoint in a Giemsa positive G-band during a balanced reciprocal translocation is most likely to cause gene disruption and lead to an abnormal phenotype, as these bands are rich in active genes.

Step-by-step explanation:

In a balanced reciprocal translocation where two chromosomes exchange pieces, breakpoints in Giemsa positive G-bands are most likely to cause gene disruption leading to an abnormal phenotype. The Giemsa positive G-bands represent areas that are rich in gene concentration, and a breakpoint here would likely disrupt gene function. In contrast, Giemsa negative G-bands, Giemsa negative R-bands, and C-bands are typically gene-poor regions, less likely to contain genes, thus a translocation involving these areas is less likely to result in an abnormal phenotype due to gene disruption.