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(Solved): please help on these three questions on my lab. please give clear and precise answer. thnx 1. A man ...


please help on these three questions on my lab. please give clear and precise answer. thnx

1. A man and a woman are both heterozygous for a recessive allele that causes cystic fibrosis. What is the probability that their first two offspring will have the disorder?

2. When examining a human pedigree, what patterns do you look for to distinguish between X-linked recessive inheritance and autosomal recessive inheritance?

3. A woman is heterozygous for an X-linked disorder, hemophilia A. If she has a child with a man without hemophilia A, what is the sex ratio that the child will be a male with hemophilia A?



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1. To determine the probability that their first two offspring will have the disorder (cystic fibrosis), we need to consider the principles of Mendelian genetics. Let's assume that the recessive allele causing cystic fibrosis is represented by "a," and the dominant normal allele is represented by "A." Since both the man and the woman are heterozygous carriers of the recessive allele, their genotypes can be represented as Aa.

When these individuals have offspring, they can each contribute one of their alleles to their children. Therefore, the possible combinations of alleles that the parents can pass on to their children are as follows: For the man (Aa): - He can pass on either the allele A or the allele a with a 50% chance for each. For the woman (Aa): - She can also pass on either the allele A or the allele a with a 50% chance for each. To determine the probability of their offspring having cystic fibrosis, we need to consider all possible combinations of alleles that the parents can pass on to their children: Possible combinations for the offspring: 1. AA (A from the father and A from the mother) - No cystic fibrosis 2. Aa (A from the father and a from the mother) - No cystic fibrosis 3. aA (a from the father and A from the mother) - No cystic fibrosis 4. aa (a from the father and a from the mother) - Cystic fibrosis

Out of these four possible combinations, only one results in the offspring having cystic fibrosis (aa). Therefore, the probability that their first two offspring will have the disorder is 1/4 or 25%.
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