The Scots Dumpy, a type of chicken (fowl) from Scotland, can exhibit short-leg l

Question

The Scots Dumpy, a type of chicken (fowl) from Scotland, can exhibit short-leg length normal-leg length phenotypes. A breeder crossed two normal-legged Scots Dumpy, and ro all of the Fi are normal-legged. When the same breeder crossed a norm al-legged fowl with a g were normal- legged. Following a third cross, involving two short-legged Scots Dumpy fowl, the breeder observed the following results among 200 offspring counted: 133.short-legged fowl 67 normal-legged fowl 8 3 a. The breeder is confused about the results. Tell the breeder what the last (or third) coss might dotype of the short- legged chickes? b. What is the genotype of the short-legged chickens?

Explanation / Answer

Answer a.
When two short-legged Scots Dumpy fowl were crossed obtaining 133 short-legged fowl and 67 normal-legged fowl indicates that the short-legged phenotype is dominant to the normal-legged phenotype. This is because recessive phenotypes need to be homozygous as per definitions.
Answer b.
Homozygous recessive self-crosses can never yield more than one phenotype. Even homozygous dominant self-crosses can never yield more than one phenotype. Hence, the short-legged chicken must have had a heterozygous genotype which can be represented in the form of Tt where T is dominant allele and t is recessive allele.

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