Question

T.H. Morgan discovered that all the genes in Drosophila are linked to four pairs of linkage groups which correspond to 4 pairs of chromosomes. Sometimes, the linkage of some genes, present at some specific distance, is broken and they show independent assortment. The most plausible reason for break in the concept of linkage would be

• A. Transposition
• B. Recombination
• C. Translocation
• D. Sister-chromatid exchange

Answer 1

The correct option is B Recombination

During meiotic cell cycle, an important step is crossing over; where there is an exchange of the genetic material between certain portions of the homologous chromosomes. As a result of this, genetic recombination occurs. If two genes are placed very close to each other (linked genes) on a chromosome Then the probability of them splitting during the genetic recombination is less likely. However, if the two genes are at a distance from each other (though on the same arm of the chromosome), then there is good chance that they might then separate during recombination and behave as independent genes rather than linked genes. Whether 2 genes will behave as linked genes or split up will depend on the relative distance between them and the possibility of a genetic recombination event. The greater the distance between the two genes the greater would be the possibility of them moving away during recombination and showing independent assortment. Thus, the correct answer is option B.