Genetic Problems?

Question

In humans, the trait for A type blood and B type blood show incomplete dominance, so that a person with both genes has blood type AB. Both A and B dominate type O. A person with a gene for type A blood and type O blood marries someone with a gene for type B blood and type O blood. List the types of offspring they could have and the probability for each blood type in the offspring.

2. Suppose that gene b is sex-linked, recessive, and lethal. A man marries a woman who is heterozygous for this gene. If this couple had many normal children, what would be the predicted sex ratio of these children?

3. A particular sex-linked recessive disease of human beings is usually fatal. Suppose that by chance, a man with the disease lives past puberty and marries a woman heterozygous for the trait. If they have a daughter, what is the probability that she will have the disease?

Answer 1

All right. Let's take these in order.

The child inherits one gene from each parent. The parents are AO and BO, so the child can be AB, AO, OB, or OO, each with equal probability. But they asked for blood type, not gene type, so those end up being 25% type AB, 25% type A, 25% type B, and 25% type O.

If a woman is carrying a sex-lined gene, we know it is on the X chromosome (that's all she has!). She's hetrozygous, so she has one normal gene (we'll call it B) and one disease gene (we'll call it b). Since the disease is lethal and on the X chromosome and a man necessarily only has one copy, we know the father can't have a b gene or he'd be dead.

So now it looks a bit like the above problem. The father is YB and the mother is Bb. That means the potential children are YB, Yb, BB, and Bb. But when we translate these into phenotypes, all the Yb children are dead, leaving us three choices of equal probability: 33% male, 33% female (no disease gene), and 33% female (carrier, like mom). Or, to answer the question, we would expect 2 girls for every boy.

In the third question, the sex-linked disease is recessive, so we can infer again that it is on the X chromosome (since nobody has two Y chromosomes, the question of dominant or recessive is irrelevant). We'll use the same nomenclature as above.

So the man is Yb, and the hetrozygous woman is Bb. Their children are YB, Yb, bB, and bb. The question only asks about daughters, so that's just the last two. They have equal probability and one had the disease while the other is a carrier, so the answer is 50%.

Hope that helps!

Answer 2

dazzling question. Leah is partly nicely suited and on the nicely suited music however the bigger situation arises while in easy terms one be sure is a service. In that scenario a container attempt will in no way artwork and the breeder has in simple terms finished greater to harm their breed by ability of passing on a mutation 50% of the time without threat of detecting it. that's very actual of accepted sires who're used very generally and/ or by ability of use of guy-made insemination the place their genes are disseminated in an extremely extreme frequency between something of the inhabitants. "container" sorting out is likewise now and returned spoke of as "attempt" matings. that's an extremely undesirable and unacceptable approach for figuring out inherited issues even till now there have been any DNA tests available. Breeders will in no way do away with inherited ailments with attempt matings for the ordinary reason that there are maximum of mutations and... you are able to no longer continuously % out people who're distributors. additionally, if a service to service attempt mating happens then the possibility of generating an affected animal is 25% so the possibility nonetheless exists that an affected in simple terms isn't made from each mating, to no longer point out by ability of that factor it particularly is too previous due... so why blindly mate without understanding no count if a mutation exists with the opportunity of propagating greater of an analogous difficulty? that's a silly recommendations-set fairly now while there are maximum of DNA tests and well-being displays available. the difficulty isn't in easy terms with the scenario "what if the two dad and mom are distributors of a recessive sickness" yet greater so "what if in easy terms one be sure is a service." it particularly is while the undertaking keeps to circulate undetected.