Question

Determine the probability of a couple having a child with a widow's peak if the conditions are as follows: The gene for widow's peak follows strict autosomal dominant-recessive inheritance. Widow's peak (W) is dominant, and no widow's peak (w) is recessive. The genotype of the mother is Ww, and the genotype of the father is ww.

Accepted Answer

Step 1: Understand the inheritance pattern. Widow's peak is an autosomal dominant trait, meaning only one dominant allele (W) is needed for the trait to be expressed. The recessive allele (w) will only result in no widow's peak if both alleles are recessive (ww). Step 2: Write down the genotypes of the parents. The mother has the genotype Ww (heterozygous), meaning she carries one dominant allele (W) and one recessive allele (w). The father has the genotype ww (homozygous recessive), meaning he carries two recessive alleles (w). Step 3: Set up a Punnett square to determine the possible genotypes of the offspring. Place the mother's alleles (W and w) on one side of the square and the father's alleles (w and w) on the other side. Step 4: Fill in the Punnett square by combining the alleles from the mother and father. This will give you the possible genotypes of the offspring: Ww (widow's peak) and ww (no widow's peak). Step 5: Calculate the probability of each genotype. Count the number of squares with Ww (dominant phenotype) and ww (recessive phenotype) and divide by the total number of squares (4). This will give you the probability of the child having a widow's peak.

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Key Concepts

Autosomal Dominant and Recessive Inheritance

Genotype and Phenotype

Punnett Square