Question

Genes A, B , C and D are present on the same chromosome. The recombination frequency between the genes is as follows: A and B: 24%, A and D: 16%, B and C: 18%, C and D: 10%. What is the correct order of genes along the chromosome

Answer 1

Answer:

BDCA

Explanation:

Recombination, also know as crossing-over, refers to the exchange of genetic material (DNA) between non-sister chromatids of homologous chromosomes during cell division (meiosis). The recombination frequency refers to the frequency of crossover between two genes/loci during meiosis. The recombination frequency is not a direct result of the physical distance between genes/loci on the same chromosome, but this value provides a good approximation of such distance. The recombination frequency is measured in centimorgans (cM), where 1 cM is equal to a 1% chance of recombination. The higher the recombination frequency between two genes/loci, the greater the chance that a cross-over will occur between them, and the greater the distance between them. Moreover, the lower the recombination frequency between two genes/loci, the lower the probability that they will separate by recombination, and the more closely they are linked.

Linkage map:

B------D-----C----A

         D-----------A

             16 cM

         D----C

         10 cM

B-------------C

    18 cM

B--------------------A

        24 cM