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A mink breeder finds that 50 % of the of...

A mink breeder finds that 50 % of the offspring are aa. What genotype were their parents ?

A

AA x aa

B

Aa x Aa

C

aa x aa

D

Aa x aa

Text Solution

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The correct Answer is:
To determine the genotypes of the parents based on the information that 50% of the offspring are homozygous recessive (aa), we can analyze the possible genetic crosses. ### Step-by-Step Solution: 1. **Understanding the Problem**: We know that 50% of the offspring are of the genotype "aa". This means that half of the offspring have received the recessive allele from both parents. 2. **Identifying Possible Parental Genotypes**: - For an offspring to be "aa", both parents must contribute an "a" allele. Therefore, at least one parent must have the "a" allele. 3. **Analyzing the Options**: - **Option 1**: AA x AA - All offspring would be AA (100%). - **Not possible**. - **Option 2**: AA x Aa - Offspring would be 50% AA and 50% Aa (no aa). - **Not possible**. - **Option 3**: Aa x Aa - Offspring would be 25% AA, 50% Aa, and 25% aa (25% aa). - **Not possible**. - **Option 4**: Aa x aa - Offspring would be 50% Aa and 50% aa (50% aa). - **Possible**. 4. **Conclusion**: The only combination that results in 50% of the offspring being "aa" is when one parent is heterozygous (Aa) and the other is homozygous recessive (aa). ### Final Answer: The genotypes of the parents are Aa (heterozygous) and aa (homozygous recessive). ---
To determine the genotypes of the parents based on the information that 50% of the offspring are homozygous recessive (aa), we can analyze the possible genetic crosses. ### Step-by-Step Solution: 1. **Understanding the Problem**: We know that 50% of the offspring are of the genotype "aa". This means that half of the offspring have received the recessive allele from both parents. 2. **Identifying Possible Parental Genotypes**: - For an offspring to be "aa", both parents must contribute an "a" allele. Therefore, at least one parent must have the "a" allele. ...
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