USA Biology Olympiad (USABO) Practice Exam

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Prepare for the USA Biology Olympiad (USABO) Exam. Enhance your skills with engaging multiple-choice questions, detailed explanations, and essential biology concepts. Get exam-ready and boost your performance with expert tips and study resources!

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What is the probability of obtaining the genotype AAbbCCdd from the parents AaBbCcDd and AABbCcDd, assuming independent assortment of all gene pairs?

1/32
1/64
1/128
1/256

The correct answer is: 1/128

To find the probability of obtaining the genotype AAbbCCdd from the parents AaBbCcDd and AABbCcDd, we can analyze each gene independently, since the genes assort independently. 1. **For the A allele**: - Parent 1 (Aa) can contribute either A or a with a probability of 1/2 for each. - Parent 2 (AA) can only contribute A with a probability of 1. - Therefore, the probability of getting an A from the first parent and an a from the second parent to produce the genotype Aa is 1/2 for A from the first parent and 1 for A from the second parent, resulting in a probability of 1/2. 2. **For the B allele**: - Parent 1 (Bb) can contribute either B or b with a probability of 1/2 for each. - Parent 2 (Bb) can also contribute either B or b with a probability of 1/2 for each. - To get the genotype Bb, we can obtain it from B (from either parent) and b (from the other). The possible combinations that yield Bb are: - B from Parent