A) What is the recombination frequency between loci A and B? B) What is the reco

Question

A) What is the recombination frequency between loci A and B?

B) What is the recombination frequency between loci B and C?

C) What is the recombi nation frequency between loci A and C?

D)Are these loci linked?

E) Demonstrate the physical arrangement of the genes on the chromosome, i.e. the order of the genes on a chromosomes as well as their map distances.

F)Write out the genotypes of the parents for this cross, indicating which al leles are linked with one another for each parent? _________X___________

Number of F1 a/a . B/b . C/c 60 A/a . b/b . c/c 56 a/a . b/b . C/c 95 A/a . B/b . c/c 89 a/a . b/b . c/c 375 A/a . B/b . C/c 315 a/a . B/b . c/c 6 A/a . b/b . C/c 4 1,000

Explanation / Answer

A). The recombination frequency between A and B = (Number of gametes produced from A, B recombination +number of double recombinants) *100/ total number of progeny.

The recombination frequency between A and B = [(60+56) +(6+4)] *100/ 1000 = 12.6%

B). The recombination frequency between loci B and C = (Number of gametes produced from B, C recombination +number of double recombinants) * 100/ total number of progeny.

The recombination frequency between B and C = [(95+89) +(6+4)] * 100/ 1000 = 19.4%

C). The recombination frequency between A and C = (60+56)/1000 * (95+89)/1000 = 0.116* 0.184 = 0.0213 or 21 per 1000, but it is given that the number of double recombinants = 10 (means, the genes are linked).

D). Yes, these loci are linked (because the number of progeny with the parental genotypes is more than that of recombinants).

E). From the double recombinant gametes, we can say that the gene order is ABC. The recombination frequency between A and B= 12.6%, means the distance between A and B = 12.6%

The recombination frequency between B and C= 19.4%, means the distance between B and C = 19.4 map units.

Now, the distance between A and C = 12.6+19.4 = 32 map units.

F). The genotypes of parents are ABC and abc.

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