Mr. and Mrs. Anderson both have tightly curled hair. (The ha Show more I. Problems Involving One Gene Mr. and Mrs. Anderson both have tightly curled hair. (The hair form gene shows incomplete dominance. There are two alleles curly and straight. The heterozygote has wavy hair.) The Andersons have a child with wavy hair. Mr. Anderson accuses Mrs. Anderson of being unfaithful to him. Is he necessarily justified? Why or why not? (2 points) Two wavy haired people (one male and one female) marry and have eight children. Of these eight how many would you expect to be curly haired how many wavy haired and how many straight haired assuming that the family follows the expected statistically predicted pattern? Suppose you examine the actual children and discover that three of the eight have curly hair. What do you suppose went wrong? (2 points) Basic body color for horses is influenced by several genes one of which has several different alleles. Two of these allelesthe chestnut (dark brown) allele and a diluting (pale cream) allele (often incorrectly called albino)display incomplete dominance. A horse heterozygous for these two alleles is a palomino (golden body color with flaxen mane and tail). Is it possible to produce a herd of pure-breeding palomino horses? Why or why not? Work the Punnett square for mating a palomino to a palomino and predict the phenotypic ratio among their offspring. (2 points) In fruit flies the gene for wing shape has an unusual allele called curly (designated Cy). The normal (wild type) allele is designated cy. A fly homozygous for cy (cy cy) has normal straight wings. The heterozygote (Cy cy) has wings which curl up on the ends (and incidentally cant really fly). The homozygote for the Cy allele (Cy Cy) never hatches out of the egg. In other words this allele is lethal in the homozygous condition. If two curly winged flies are mated and the female lays 100 eggs predict the following showing appropriate work: How many eggs will produce living offspring? (1 point) How many straight winged flies do you expect among the living offspring? (1 point) What percentage of the living offspring do you expect to be curly winged like the parents? (1 point) In cattle there is an allele called dwarf which in the heterozygote produces calves with legs which are shorter than normal. This again is a homozygous lethal (the homozygous dwarf calves spontaneously abort early or a stillborn). If a dwarf bull is mated to 400 dwarf cows what phenotypic ratio to you expect among the living offspring? (1 point) II. Problem Involving Two Genes A man with dark (dominant) curly (see the first 2 problems in Section I) hair marries a woman with light straight hair. Their daughter who happens to have dark hair marries a man with light wavy hair. Answer the following questions about this dark-haired daughter and her family. Draw a Punnetts square for this marriage and predict the phenotypic ratio among the offspring of the daughter and her husband. (4 points) What is the chance that they will have a child with hair just like his or her fathers? (1 point) III. Problems Involving Sex Linkage In fruit flies (Drosophila) one eye color gene is X-linked with a recessive white allele and a dominant red allele. If white-eyed female flies are bred to red-eyed male flies describe the expected offspring (assume all parental flies are true-breeding). What results do you expect if you do the reciprocal cross (reverse the phenotypes of the parent flies)? (2 points) Earl has normal color vision while his wife Erma is colorblind. . Colorblindness is an X-linked trait and the normal allele is dominant to the colorblindness allele. If they have a large family in what ways should the colorblindness trait affect their children? (2 points) Ethan is colorblind. His wife Edna is homozygous for the normal color vision allele. If they have eight children how man of them would you expect to be colorblind? Using Punnett squares derive and compare the genotypic and phenotypic ratios expected for the offspring of this marriage and those expected for the offspring of the marriage described in Problem III.2. (2 points) Marians father is colorblind as is her maternal grandfather (her mothers father). Marian herself has normal color vision. Marian and her husband Martin who is also colorblind have just had their first child a son they have named Mickey. Please answer the following questions about this small family. What is the probability that this child will be colorblind? (2 points) Three sources of the colorblindness allele are mentioned in this family. If Mickey is colorblind from which of these three men (Marians grandfather Marians father or Martin) did he inherit the allele? (1 point) If Martin were not colorblind how would this affect the prediction about Mickey? (1 point) In cats there is a coat color gene located on the X chromosome. This gene has two allelesorange and black. A heterozygous cat has tortoiseshell color (a splotchy mixture of orange and black). Predict the genotypic and phenotypic frequencies among the offspring of the following crosses. Pay careful attention to the genders of the offspring. Black female Orange male (1 point) Orange female Black male (1 point) Tortoiseshell female Black male (1 point) Tortoiseshell female Orange male (1 point) IV. Problems Involving Genes with Multiple Alleles In a particular family one parent has Type A blood the other has Type B. They have four children. One has Type A one has Type B one has Type AB and the last has Type O. What are the genotypes of all six people in this family? (2 points) NOTE: The ABO blood type gene has three alleles. I A and I B are codominant; i (for Type O) is recessive to both. In a recent case in Spokane Washington a young woman accused a soldier of being the father of her child. The soldier denied it. The soldiers lawyer demanded that blood types be taken to prove the innocence of his client. The following results were obtained: Alleged father Type O. Mother Type A. Child Type AB. The court found the soldier guilty on the basis of the womans remarkable memory for dates and details that apparently eliminated all other possible fathers. What are the possible genotypes for these three people? (2 points) Do you agree with the courts decision? Why or why not? (2 points) It was suspected that two babies had been exchanged in a hospital. Mr. and Mrs. Jones received baby #1 and Mr. and Mrs. Simon received baby #2. Blood typing tests on the parents and the babies showed the following: Mr. Jones: Type A Mr. Simon: Type AB Mrs. Jones: Type O Mrs. Simon: Type O Baby #1: Type A Baby #2 Type O Were the babies switched? How do you know whether they were or they werent? (2 points) A man with type O blood marries a woman with Type AB blood. Among their children what proportion would you expect to have blood types like one or the other of these parents? What proportion would you expect to have blood types different from both parents? Explain. (2 points) A woman has a daughter. There are three men whom she claims might have been the father of the child. The judge in the paternity court orders that all three men the child and the mother have blood tests. The results are: mother Type A; Daughter Type O; Man #1 Type AB; Man #2 Type B; Man #3 Type O. The mother claims that this proves that Man #3 must be the little girls father. Is the mother correct? Why or why not? (2 points) The judge isnt satisfied so he asks for the medical records of the people involved. He discovers that the little girl is colorblind. Men #s 1 and 2 are also colorblind; Man #3 has normal color vision as does the mother. (NOTE: Colorblindness is X-linked and recessive.) Assuming that one of these three men must be the father can you now determine which of the three it is? (2 points) Another woman has the same problem. Her blood type is A her childs is B. She again has three candidates for fatherhood. Their blood types are: Man #1 B; Man #2 AB; Man #3 O. Based on blood types the mother says it must have been #1. Do you agree? Why or why not? (2 points) This child a son this time is also colorblind. The only one of the men in question to share this characteristic is #2. The mother is not colorblind. Can you now determine who the father of the little boy is assuming it must be one of these men? Explain your answer. (2 points) Show less
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