A normally pigmented woman whose father was an albino marries a normally pigmented man whose mother was an albino. What is the probability that they would have an albino child?
(a) 50 percent
(b) 25 percent
(c) 12.5 percent
(d) 6.25 percent
(e) 100 percent

Verified step by step guidance

Step 1: Understand that albinism is typically inherited as an autosomal recessive trait. This means an individual must inherit two recessive alleles (aa) to express albinism, while carriers have one dominant (A) and one recessive allele (a) and do not show the trait.

Step 2: Determine the genotypes of the parents based on the information given. The woman is normally pigmented but her father was albino, so she must be a carrier (Aa). The man is normally pigmented but his mother was albino, so he must also be a carrier (Aa).

Step 3: Set up a Punnett square for the cross between the two carriers (Aa x Aa). The possible genotypes of their children are: AA (normal, non-carrier), Aa (normal, carrier), and aa (albino).

Step 4: Calculate the probability of each genotype from the Punnett square. The genotypic ratio is 1 AA : 2 Aa : 1 aa, meaning there is a 1 in 4 chance (25%) for a child to be albino (aa).

Step 5: Conclude that the probability the couple will have an albino child is 25 percent, corresponding to option (b).

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Autosomal Recessive Inheritance

Albinism is typically inherited as an autosomal recessive trait, meaning a child must inherit two copies of the recessive allele (one from each parent) to express the condition. Individuals with one recessive and one dominant allele are carriers and usually have normal pigmentation.

Carrier Probability and Pedigree Analysis

Knowing that the parents have albino parents means each parent is likely a carrier of the recessive allele. Analyzing the family history helps determine the probability that each parent carries one recessive allele, which is essential for calculating the chance their child inherits two recessive alleles.

Punnett Square and Probability Calculation

A Punnett square is used to predict the genotypes of offspring based on parental alleles. By combining the probabilities that each parent is a carrier and the chance of passing the recessive allele, one can calculate the overall probability of having an albino child.

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