Case 2: Polycystic Kidney Disease (dominant lethal allele) Maria is 38 years old. She and her husband Joe have 4 children. Maria has been diagnosed with polycystic kidney disease. She learns that cysts developing in her kidneys have damaged them severely. The damage will continue until the kidneys stop functioning. Maria faces dialysis and will eventually need a kidney transplant. Maria is tested for the allele that causes the disease and learns that her form of the disease is caused by a dominant mutation on chromosome 16. Maria is heterozygous for the trait. Her husband is confirmed to be homozygous recessive. Maria's children offer the best hope of a match for a future kidney donation but must be free of the harmful allele. 5. What is the probability of Maria and Joe's children inheriting this dominant harmful allele? Solve a Punnett Square to estimate this probability. Show your work below. INCOMPLETE DOMINANCE There are some situations in which the two alleles of a gene produce a "blended" effect in a heterozygous individual. Because neither allele is dominant over the other, capital and lowercase letters cannot be used as symbols. One of denoting alleles showing incomplete dominance is to designate both with a capital letter with a superscript or apostrophe added to one - such as A and A'. For this example of gene "A" then, this case of incomplete dominance has 3 possible phenotypes, one each for the genotypes AA, AA' and A'A'. Case 1: Delta 32 and the AIDS virus Stephen Crohn is a gay man whose partner was the 5 person in the U.S. to die from AIDS. In spite of his exposure to the virus, Crohn has never shown any signs of the disease. Dr. O'Brien of the National Institute of Health found that Crohn's resistance is due to a mutation called delta 32. It results in the blocking of a membrane channel through which HIV enters white blood cells. Inheriting two copies of delta 32 (D'D') provides exceptional/complete resistance to HIV. The heterozygous condition (DD') delays the onset of AIDS after initial infection because there are half the number of membrane passageways as are present in a person who is homozygous normal which slows down the rate of viral replication. The heterozygous genotype (DD') can therefore be described as giving modest/partial resistance. The DD genotype provides no resistance to AIDS. Both of Stephen Crohn's parents were heterozygous for the delta 32 mutation. Stephen's genotype became known after his unexpected resistance to HIV. 6. In the cross between Stephen's parents, what would have been the probability for one child between them of having Stephen's homozygous genotype? Solve a Punnett Square to estimate this probability. Show your work below.