In the nematode roundworm C. elegans, mutation of the dpy-18 gene causes Dumpy (

Question

In the nematode roundworm C. elegans, mutation of the dpy-18 gene causes Dumpy (short and fat) worms, and mutation of the unc-24 gene causes Uncoordinated movement. Both alleles are recessive. An animal of genotype unc-24 + / + dpy-18 is testcrossed and gives 1000 progeny if the following phenotypes wild type 115 Dumpy 379 Uncoordinated 401 Dumpy Uncoordinated 105 What is the map distance between dpy-18 and unc-24? a) 10.5 map units b) 0.22 map units c) 0.78 map units d) 78 map units e) 22 map units
In the nematode roundworm C. elegans, mutation of the dpy-18 gene causes Dumpy (short and fat) worms, and mutation of the unc-24 gene causes Uncoordinated movement. Both alleles are recessive. An animal of genotype unc-24 + / + dpy-18 is testcrossed and gives 1000 progeny if the following phenotypes wild type 115 Dumpy 379 Uncoordinated 401 Dumpy Uncoordinated 105 What is the map distance between dpy-18 and unc-24? a) 10.5 map units b) 0.22 map units c) 0.78 map units d) 78 map units e) 22 map units
In the nematode roundworm C. elegans, mutation of the dpy-18 gene causes Dumpy (short and fat) worms, and mutation of the unc-24 gene causes Uncoordinated movement. Both alleles are recessive. An animal of genotype unc-24 + / + dpy-18 is testcrossed and gives 1000 progeny if the following phenotypes wild type 115 Dumpy 379 Uncoordinated 401 Dumpy Uncoordinated 105 What is the map distance between dpy-18 and unc-24? a) 10.5 map units b) 0.22 map units c) 0.78 map units d) 78 map units e) 22 map units

Explanation / Answer

The parental cross is UuDd or a heterozygote for both genes. It is crossed to a homozygous recessive organism. With linked genes, we can see two recombinant classes and two parental classes. Here, the wildtype and the uncoordinated dumpy are the parental. The other two classes are recombinants.

The distance between the two genes(recombination frequency) is calculated as -No. of recombinants/total progeny (x 100)

= 379+401/1000

= 0.78 x 100

= 78 m.u.

Hence, the answer is d.

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