Chapter 5: Problem 4

If the phenotype trait of an \(A a\) heterozygous individual is the same as that of an \(A A\) homozygous individual, which allele is recessive?

Short Answer

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Answer: The recessive allele is "a."

Step by step solution

Understanding Dominant and Recessive Alleles

Dominant alleles are those that always express their traits in the presence of another allele, which is recessive. Recessive alleles are those that require two copies, or both present alleles, to be the same for their traits to be expressed in an organism's phenotype.

Analyzing the Homozygous Individual Genotype

The homozygous individual in the given exercise has an \(AA\) genotype. When an individual is homozygous, it means that both of their alleles for a particular gene are the same. In this case, we focus on the phenotype of the \(AA\) genotype to draw a comparison with the heterozygous genotype.

Analyzing the Heterozygous Individual Genotype

The heterozygous individual in the given exercise has an \(Aa\) genotype. This means that the individual has two different alleles for the gene. Here we'll investigate whether the phenotype of the \(Aa\) genotype is the same as the \(AA\) genotype.

Comparing Phenotype Traits

The exercise states that the phenotype trait of an \(Aa\) heterozygous individual is the same as that of an \(AA\) homozygous individual. This means that the \(A\) allele in the \(Aa\) heterozygous individual is responsible for the expressed phenotype.

Identifying the Recessive Allele

Based on the information provided, the recessive allele must be one that does not affect the phenotype in the presence of the dominant allele. Since the \(Aa\) heterozygous individual has the same phenotype as the \(AA\) homozygous individual, the \(A\) allele must be dominant. The allele not affecting the phenotype in the presence of the \(A\) allele is the \(a\) allele. Therefore, the \(a\) allele is the recessive allele.

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If the phenotype trait of an \(A a\) heterozygous individual is the same as that of an \(A A\) homozygous individual, which allele is recessive?

Short Answer

Step by step solution

Understanding Dominant and Recessive Alleles

Analyzing the Homozygous Individual Genotype

Analyzing the Heterozygous Individual Genotype

Comparing Phenotype Traits

Identifying the Recessive Allele

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