S. In a series of onmapping experiments, the recombination frequencies for four

Question

S. In a series of onmapping experiments, the recombination frequencies for four different linked genes of rosophila were determined as shown in the figure below the recombination b black body cn cinnabar eyes reduced bristles | 9 01 vg.vestigial wings rb | 3.5 | 65 | 0 g 19 9.0 16 0 rbvg The numbers in the boxes are the recombination frequencies in between the genes (in percent) i. What is the order of these genes on a chromosome map? (0.5pts) ii. A fly that has a tan body and red eyes, is heterozy gous for both the b and en alleles. If these genes are in the repulsion linkage phase, draw the pair of homologous chromosomes in this fly that have these 2 genes on them and indicate what alleles are on each (0.5 pts.). tn ili. If one of these heterozy gous flies from (B) is testcrossed, what proportion of the resulting F2 offspring will be... (0.5 pts.) Tan-bodied and red-eyed: Bb CNen Black bodied and red-eyed2 Tan boded/red ae

Explanation / Answer

Ans 5. (i)

Recombination frequency is directly proportional to distance between genes. More is the distance b/w two linked genes, more is recombination among them.

Here, recombination between b and vg is highest at 19%. This means those two genes are the furthest apart from each other among the four genes.

Next is b/w vg and rb at 16%. Then between vg and cn at 9% and between cn and b 9% ; which means that vg and b are equidistant to cn.

Then between rb and cn at 6.5% and between rb and b at 3.5%(indicating rb and b are closest on the chromosome map).

Therefore likely gene order is:-

vg cn rb b

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