If two heterozygous parents (Aa) for a recessive trait have a child, what is the probability the child will be homozygous recessive (aa)?

Enhance your HESI exam preparation with targeted remediation. Utilize our flashcards and detailed multiple choice questions for better understanding. Ensure success in your HESI exams!

Multiple Choice

If two heterozygous parents (Aa) for a recessive trait have a child, what is the probability the child will be homozygous recessive (aa)?

When two heterozygous parents (Aa) for a recessive trait have a child, each parent can pass on either the dominant allele (A) or the recessive allele (a) with equal chance. Crossing one allele from each parent gives four equally likely combinations: AA, Aa, Aa, and aa. The combination that is homozygous recessive is aa, which occurs in 1 of the 4 possibilities. So the probability is 1/4, or 25%. Since a recessive trait is expressed only when both alleles are recessive, the phenotype would show if the child has aa, but the question asks for the chance of the genotype aa, which is 25%.

When two heterozygous parents (Aa) for a recessive trait have a child, each parent can pass on either the dominant allele (A) or the recessive allele (a) with equal chance. Crossing one allele from each parent gives four equally likely combinations: AA, Aa, Aa, and aa. The combination that is homozygous recessive is aa, which occurs in 1 of the 4 possibilities. So the probability is 1/4, or 25%. Since a recessive trait is expressed only when both alleles are recessive, the phenotype would show if the child has aa, but the question asks for the chance of the genotype aa, which is 25%.

More practice questions