Let\'s assume/pretend that webbed toes are a recessive trait (we are assuming th
ID: 132011 • Letter: L
Question
Let's assume/pretend that webbed toes are a recessive trait (we are assuming this because it's not fun to pretend your niece was born with an actual genetic disease). You do not have webbed toes and your fraternal twin brother does not have webbed toes. It is a surprise when your new niece is born to your brother and his wife with two webbed toes.
What is your brother's genotype and phenotype? What is your sister-in-law's genotype and phenotype? What is your niece's phenotype and genotype?
Do you have enough information to know your genotype? Speculate on the possibilities. What are the chances that your children will be born with webbed-toes? How do you know?
Explanation / Answer
Normal toes = WT = Dominant trait = T
Webbed toes = Mutant = Recessive trait = t
Genotype of you = Tt = Carrier and unaffected
Genotype of your fraternal twin brother = Tt = Carrier and unaffected
Genotype of your sister in law = tt = Affected
Genotype of your niece = tt = Affected
Parental cross (Your brother and sister in law): Tt X tt
Progeny: Tt Tt tt tt
Your niece = tt
The probability for your progeny to be affected is dependent on the genotype of your mate.
If she is a carrier (Tt), 1/4th of your progeny are affected, 1/4 progeny are WT homozygous, and 1/2 progeny are carriers.
If she is a WT (TT), 1/2 progeny are WT homozygous, and 1/2 progeny are carriers.
If she is affected (tt), 1/2 progeny are affected, and 1/2 progeny are carriers.
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