Question

Which one of the following information is essential to determine the genetic map distance between two genes located on the same chromosome ?

• A. Length of the particular chromosome
• B. Number of genes present in the particular chromosome
• C. Number of nucleotides in the particular chromosome
• D. Percentage of crossing over or recombinant frequency between the two genes

Answer 1

Answer: (D)

Percentage of crossing over or recombinant frequency between the two genes

When the genes are located on different chromosomes or far apart on the same chromosome they are unlinked and follow Mendel's law of independent assortment. But when two genes are located close together they are called linked genes. That is, more often than not crossing over during meiosis results in progeny with the parental set of allele and deviates from Mendel's laws.

In such cases, the chance of getting a recombinant progeny is very low compared to others. This phenomenon can be used to get a rough idea about the physical distance between genes and likewise build a linkage map.
To make a linkage map, identifying the Recombinant frequency is most essential.
Recombination frequency (RF)= Recombinants ×100%

Total offspring

Higher the Recombinant frequency, longer is the distance between genes.

So, the correct answer is option D.