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If 'A' represents the dominant gene and ...

If 'A' represents the dominant gene and 'a' represents its recessive allele, which of the following would be the most likely result in the first generation offspring when Aa is crossed with aa?

A

All will exhibit dominant phenotype.

B

All will exhibit recessive phenotype.

C

Dominant and recessive phenotypes will be 50% each.

D

Dominant phenotype will be 75%.

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem, we need to determine the possible genotypes and phenotypes of the offspring when we cross two individuals with the genotypes Aa (heterozygous) and aa (homozygous recessive). ### Step-by-Step Solution: 1. **Identify the Genotypes**: We have two parents with the following genotypes: - Parent 1: Aa (heterozygous) - Parent 2: aa (homozygous recessive) 2. **Determine Gametes**: - The first parent (Aa) can produce two types of gametes: A (dominant) and a (recessive). - The second parent (aa) can only produce one type of gamete: a (recessive). 3. **Set Up a Punnett Square**: - We will create a Punnett square to visualize the potential offspring. - The rows will represent the gametes from Parent 1 (Aa), and the columns will represent the gametes from Parent 2 (aa). | | a | a | |-------|-------|-------| | **A** | Aa | Aa | | **a** | aa | aa | 4. **Fill in the Punnett Square**: - The combinations will be: - From A (Parent 1) and a (Parent 2): Aa - From a (Parent 1) and a (Parent 2): aa - Thus, the offspring genotypes will be: - 2 Aa (heterozygous) - 2 aa (homozygous recessive) 5. **Determine the Phenotypes**: - The phenotype associated with Aa (dominant) is the dominant trait. - The phenotype associated with aa (recessive) is the recessive trait. - Therefore, we have: - 2 offspring with dominant phenotype (Aa) - 2 offspring with recessive phenotype (aa) 6. **Calculate Ratios**: - The ratio of the phenotypes is: - 2 dominant (Aa) : 2 recessive (aa) or simplified to 1:1. - This means 50% of the offspring will exhibit the dominant phenotype and 50% will exhibit the recessive phenotype. ### Conclusion: The most likely result in the first generation offspring when Aa is crossed with aa is that 50% will exhibit the dominant phenotype and 50% will exhibit the recessive phenotype. ### Final Answer: **Dominant and recessive phenotypes will be 50% each.**
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