Question

46. (7 points) Vanessa has obtained two true-breeding strains of mice, each homozygous for an
independently discovered recessive mutation that prevents the formation of hair on the body.
One of the mutant strains is called naked, and the other mutation strain is called hairless. To
determine whether the two mutations are simply alleles for the same gene, Vanessa crosses

naked and hairless mice with each other (cross 1). All the offspring are phenotypically wild-
type.

A) What is the most likely explanation for the phenotypes of the F1 mice? Are the naked and
hairless mutations alleles for the same gene?

B) Vanessa next intercrosses the F1 mice (cross 2) and based in the F2 phenotype ratios,
concludes that there is no gene interaction. Fill out the following information for the F1
intercross and F2 progeny. Use these symbols: n = naked mutation, N = wild-type allele, h =
hairless mutation, H = wild-type allele.
Cross 1: parental genotypes:
F1 genotypes:

Cross 2: Write out a Punnett square for the F1 intercross and give the F2 phenotype ratio:
F2 phenotype ratio __________________

46. (7 points) Vanessa has obtained two true-breeding strains of mice, each homozygous for an independently discovered recessive mutation that prevents the formation of hair on the body. One of the mutant strains is called naked, and the other mutation strain is called hairless. To determine whether the two mutations are simply alleles for the same gene, Vanessa crosses naked and hairless mice with each other cross 1). All the offspring are phenotypically wild type. A) What is the most likely explanation for the phenotypes of the Fl mice? Are the naked and hairless mutations alleles for the same gene? B) Vanessa next intercrosses the Fl mice (cross 2) and based in the F2 phenotype ratios, concludes that there is no gene interaction. Fill out the following information for the F1 intercross and F2 progeny. Use these symbols: n naked mutation, N-wild-type allele, h = hairless mutation, H = wild-type allele. Cross 1: parental genotypes: F, genotypes: Cross 2: Write out a Punnett square for the F, intercross and give the F2 phenotype ratio: F2 phenotype ratio

Answer 1

Answer 1. n = N = h = H = naked mutation wild type allele hairless mutation wild type allele. naked and Hairless all homozygous recessine mutation, which means it will act in recessine form only. Naked and Hairless are not allele for the Same gene because when naked and hairless Crossed with each other normal phenotype (wild type) was found. They complement function of each other. Likely genotype of the Phenotype naked mutant nnth Hairless Hairlens mutant = NN hh. Hairless (No-hair) When F1 Cross was done, then there may be following process. Parent; - naked mutant (nn HH) X Hairless mutant (NN hh) allele Nh F1 phenotype NnHh (phenotypically mild type) (mild type - normal) This mutation is in two different genes.

Answer 2. F1 genotype = NnHh FIX X (FI intercoss) FI NnHh NnHh Alleles F2 Punnett square Inh Alleles & NHI Nh NH NH NN - H. NNHH Normal Normal NnHH Normal Nn th Normal Nh NNHhNN'hh Normal No Hour Nnth Normal Nr hh | No-Hair И Nn HH Nnth Normal Normal mnHH in th I No-hair nch NnHh I Normal Nrith Innth Innhh No- hair no-hair no-hair F2 phenotype ratio = q (Normal) : 7 (No-hair)