If your mom had alleles containing 18 and 21 repeats and your dad had alleles containing 18 and 24 repeats, what is the change you will be homozygous for the 18 repeat allele?
To determine the chances of being homozygous for the 18 repeat allele, we need to understand how alleles are inherited.
Alleles are different versions of a gene, and we inherit two copies of each gene (one from each parent). The number of repeats in an allele can vary, as in this case where we have 18 and 21 repeats from the mother, and 18 and 24 repeats from the father.
To calculate the probability of being homozygous for the 18 repeat allele, we need to consider the possible combinations of alleles we can inherit from our parents.
Based on the information provided, there are four possible combinations:
1. Inheriting the 18 repeat allele from both parents.
2. Inheriting the 18 repeat allele from the mother and the 24 repeat allele from the father.
3. Inheriting the 21 repeat allele from the mother and the 18 repeat allele from the father.
4. Inheriting the 21 repeat allele from both parents.
Since the question specifically asks about being homozygous for the 18 repeat allele, we are interested in the first and second combinations.
Therefore, the chances of being homozygous for the 18 repeat allele can be calculated by summing up the probabilities of these combinations.
Since each allele has an equal probability of being passed down, which is 1/2 or 0.5, the probabilities for the first two combinations can be calculated as follows:
1. Inheriting the 18 repeat allele from both parents: (0.5) * (0.5) = 0.25 or 25% chance.
2. Inheriting the 18 repeat allele from the mother and the 24 repeat allele from the father: (0.5) * (0.5) = 0.25 or 25% chance.
Therefore, the total chance of being homozygous for the 18 repeat allele is 0.25 + 0.25 = 0.5 or 50%.