A geneticist Dr. O. Sophila discovers a new mutation that causes the flies to sh

Question

A geneticist Dr. O. Sophila discovers a new mutation that causes the flies to shake and quiver. She calls this mutation spastic (sps) and determines that spastic is due to an autosomal recessive mutation. She wants to determine if the spastic gene is linked to the gene for vestigial wings (vg) - also a recessive phenotype. She has true breeding stocks for each kind of mutations. She crosses a spastic fly with a vestigial wing fly and then uses the resulting F1 females in a testcross. She obtains the following F2 flies from the testcross: Spastic with normal wings 230 NonSpastic with vestigial wings 224 Spastic with vestigial wings 97 NonSpastic with normal wings 99 Are the genes that cause vestigial wings and the spastic mutation linked? Provide the rationale to your answer. What is the genotype and phenotype of F1 females? Annotate the genotype notation illustrates whether sps and vg alleles are in cis or trans arrangement to each other. What is(are) phenotype(s) of th

Explanation / Answer

Answer:

3.1)

Spastic (recessive) = s; Nonspastic (dominant)=s+

Vestigial wings (recessive)= v; Normal wings(dominant) = V

ssVV (spastic fly) x   s+ s+ vv (Vestigial wings)-----P

sV                                   s+v----------------------------gametes

             s+sVv (nonspastic, normal wing)---------F1

F1 X ssvv------------Test cross.

During test cross, all the progeny should be in equal proportion, but it is not the case. So the genes were linked.

3.2).

F1 phenotype= nonspastic, normal wing

Genotyope: s+sVv

Recessive allele of one gene and dominant allele of the other gene present on the same chromosome, so the configuration of the genes is trans configuration.

3.3).

The recombinant phenotypes of F2 files are= spastic with vestigial wings and nonspastic with normal wings

3.4).

spastic with normal wings = ss Vv

Nonspastic with vestigial wings = s+svv

Spastic with vestigial wings = ssvv

Nonspastic with normal wings= s+sVv

3.5).

%Recombinant frequency = map distance (map units)

Recombinat frequency = (total number of recombinants / Total progeny)100

= 97+99 = (196/650)100 = 30.15%

The genetic distance between the v and s genes is 30.15 map units

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