2 Q. 1 – T.H. Morgan and his colleagues worked out a set of symbols to represent fly genotypes. Which of the following are representative?AaBb × AaBb46, XY or 46, XXvg+vgse+se × vgvgsese+2 × +3IAIB × IAIAAnswer: c
3 Q. 2 - In some Drosophila species there are genes on the Y chromosome that do not occur on the X chromosome. Imagine that a mutation of one gene on the Y chromosome reduces the size by half of individuals with the mutation. Which of the following statements is accurate with regard to this situation?This mutation occurs in all offspring of a male with the mutation.This mutation occurs in all male but no female offspring of a male with the mutation.This mutation occurs in all offspring of a female with the mutation.This mutation occurs in all male but no female offspring of a female with the mutation.This mutation occurs in all offspring of both males and females with the mutation.Answer: BThe point of this question is to help students understand sex-linkage by looking at the effect of genes on the Y chromosome. Answer a is incorrect because half of the sperm of the mutant male will contain an X chromosome and produce normal size daughters. Answer c is incorrect because females do not have a Y chromosome and cannot carry the mutation. Answer d is incorrect because, again, females do not have a Y chromosome and thus cannot carry the mutation. Answer e is incorrect because females cannot carry the mutation (no Y chromosome) and only the half of the eggs that are fertilized by a Y-bearing sperm will receive the mutation (i.e., only half of the male offspring). Answer b is correct because all the sons of the mutant male receive his Y chromosome.
4 Q. 3 - In cocker spaniels solid coat color is dominant over spotted coat color. If two heterozygous dogs were crossed to each other, what would be the probability of having a litter of 3 pups, 2 with solid coats and one with a spotted coat?3/89/169/329/64
5 Q. 4 – Two human parents with normal skin pigmentation have an albino child. What is the probability that their next child will be an albino too?1/81/161