Question

Bar is a gene often used in recombination study. Which of the following is true for the Bar gene?

(a) It is normally present in two copies

(b) Three copies of bar are called ultra bar

(c) Heterozygous bar females have a less severe effect than homozygous bar female

(d) Homozygous bar are of common occurrence

The question was asked in quiz.

I want to ask this question from Linkage and Crossing Over topic in section Genetic Recombination of Cytogenetics

Answer 1

Correct choice is (b) Three copies of bar are called ultra bar

Easiest explanation: Bar is present in single copy in normal genes. Recombination results in two bar genes which in homozygous condition can produce a severe reduction in number of eye facets. Recombination can also result in 3 copies of bar gene in a chromosome which reduces the number to 45, known as the ultra bar.