A species of centipede has a haploid chromosome number of 2. Leg length is controlled by a single gene with two alleles: the long leg allele (L) is dominant to the short leg allele (l). Body coloration is controlled by a single gene with two alleles: the dark allele (D) is dominant to the light allele (d). Leg length and body coloration are encoded by genes on separate chromosomes. Assume the traits obey Mendel’s Law of Independent Assortment. a) A centipede that is homozygous for the recessive allele at both loci mates with a centipede that is homozygous for the dominant allele at both loci. They produce 100 offspring. What fraction of the offspring would you expect to have short legs and light body coloration? Show your calculations and reasoning. b) Two centipedes that are each heterozygous for both leg length and body coloration mate and produce 100 offspring. What fraction of the offspring would you expect to have long legs and light body coloration? Show your work using a Punnett Square and provide your answer as a fraction.
A species of centipede has a haploid chromosome number of 2. Leg
length is controlled by a single gene with two alleles: the long leg allele (L) is
dominant to the short leg allele (l). Body coloration is controlled by a single
gene with two alleles: the dark allele (D) is dominant to the light allele (d). Leg
length and body coloration are encoded by genes on separate chromosomes.
Assume the traits obey Mendel’s Law of Independent Assortment.
a) A centipede that is homozygous for the recessive allele at both loci mates
with a centipede that is homozygous for the dominant allele at both loci.
They produce 100 offspring. What fraction of the offspring would you
expect to have short legs and light body coloration? Show your
calculations and reasoning.
b) Two centipedes that are each heterozygous for both leg length and body
coloration mate and produce 100 offspring. What fraction of the offspring
would you expect to have long legs and light body coloration? Show your
work using a Punnett Square and provide your answer as a fraction.
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But for part A if you cross dd ll x DD LL, won't all the offspring be DdLl (dark colored and long legged), so wouldn't NONE of the offpspring have short legs and light body coloration? Isn't the 9:3:3:1 ratio only for two heterozygous dihybrid crosses? Where is the 25/4 coming from? Could you draw a punnett square to demonstrate.
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