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Suppose that in unicorns, two autosomal loci interact to determine the type of tail. one locus controls whether a tail is present at all. the allele for a tail, t, is dominant over the allele for no tail, t. if a unicorn has a tail, then alleles with an unknown dominance relationship at a second locus determine whether the tail is curly or straight. define the alleles for tail texture as us for a straight tail and uc for a curly tail. farmer baldridge has two unicorns with curly tails. when he crosses them, one-half of the progeny have curly tails, one-quarter have straight tails, and one-quarter do not have a tail.
Suppose that in unicorns, two autosomal loci interact to determine the type of tail. one locus controls whether a tail is present at all. the allele for a tail, t, is dominant over the allele for no tail, t. if a unicorn has a tail, then alleles with an unknown dominance relationship at a second locus determine whether the tail is curly or straight. define the alleles for tail texture as us for a straight tail and uc for a curly tail. farmer baldridge has two unicorns with curly tails. when he crosses them, one-half of the progeny have curly tails, one-quarter have straight tails, and one-quarter do not have a tail.
Let's represent the locus representing the presence of a tail as T (tail) and t (no tail) while the texture of the tail as C (curly) and S (straight). We also know that T is dominant to t.Three-fourths of the progeny yielded a tailed horse, presenting at least one dominant T allele for the unicorns, being either homozygous or heterozygous (TT or Tt). The remaining one-fourth unicorn (tailess) is homozygous recessive (tt). This phenotypic ratio of 3:1 is consistent with the heterozygous cross of Tt x Tt.The tail texture is slightly more complicated with not knowing which allele is dominant. We were given a ratio of 2:1 of curly-tail to straight-tail: a slight variation of the typical genotypic ratio of 1:2:1 in a normal progeny between two heterozygous parents. The variation suggests that one genotype is missing within the progeny. Given that there more curly-tail than straight tail progeny, this suggests that C is dominant over S. This also suggests that homozygous dominant allele for curly tail (CC) is lethal.The genotypes of the parents then can be concluded with both being heterzygous to both locus (TtCS x TtCS)The progeny ratio would then be6/16 : T- ,CS3/16 : T- ,SS3/16 : tt ,S-4/16 : Lethal combination (CC included in allele)...