A girl named Sneha has brown eyes (a dominant trait). Her father has brown eyes, her mother has blue eyes (recessive). Sneha ends up having blue eyes. Explain how this could happen in terms of allele inheritance.
Answer
Sneha inherited a recessive blue eye allele from her father and a recessive blue eye allele from her mother, making her homozygous recessive.
Step-by-step solution
- Step 1: Identify the alleles of each parent. Brown eye allele (B) is dominant; blue eye allele (b) is recessive.
- Step 2: The father has brown eyes, so his genotype can be BB or Bb. Since he passed a blue allele to Sneha, his genotype must be Bb.
- Step 3: The mother has blue eyes, which means her genotype is bb.
- Step 4: Sneha inherits one allele from each parent: she gets a blue allele (b) from her father and a blue allele (b) from her mother.
- Step 5: Her genotype is bb, which is homozygous recessive, resulting in blue eyes despite the father's dominant brown eyes.
Common mistake: Thinking the father's brown eyes mean he cannot pass a blue allele.
Concept tested: Homozygous recessive inheritance
Published · How this solution was prepared and checked
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