Problem Set 3 10:35 AM January 27, 2011

Transcription

1 BIO322: Genetics Douglas J. Burks Department of Biology Wilmington College of Ohio Problem Set 3 10:35 AM January 27, 2011 Chapter 4: Problems 3, 5, 12, 23, 25, 31, 37, and 41. Chapter 5: Problems 8, 14, 24, and 33. Problem #3. The figure that follows shows the metaphase chromosomes of a male of a particular species. These chromosomes are prepared s they would be for a karyotype, but they have not yet been ordered in pairs of decreasing size. a. How many centromeres are shown? b. How many chromosomes are shown? c. How many chromatids are shown? d. How many homologous chromosomes are shown? e. How many chromosomes on the figure are metacentric? Acrocentric? f. What is the likely mode of sex determination in this species? What would you predict to be different about the karyotype of female in this species? 1 P a g e B I O S p r i n g

2 Problem #5. Indicate which of the cells numbered i v matches each of following stages of mitosis: a. anaphase b. prophase c. metaphase d. G 2 e. telophase/cytokinesis Problem #12. The five cells shown in figure a e below are from the same individual. For each cell, indicate whether it is in mitosis, meiosis I, or meiosis II. What stage of cell division is represented in each case? What is n in this organism? 2 P a g e B I O S p r i n g

3 Problem #23. A system of sex determination known as haplodiploidy is found in honeybees. Females are diploid, all! males (drones) are haploid. Male offspring result from the development of unfertilized eggs. Sperm are produced by mitosis in males and fertilize eggs in the females. Ivory eye is a recessive characteristic in honeybees; wild-type eyes are brown. a. What progeny would result from an ivory-eyed queen and a brown-eyed drone? Give both genotype and phenotype for progeny produced from fertilized and nonfertilized eggs. b. What would result from crossing a daughter from the mating in part a with a browneyed drone? Problem #23. Barred feather pattern is a Z-linked dominant trait in chickens. What offspring would you expect from (a) the cross of a barred hen to a non barred rooster (b) the cross of an FI rooster from part (a) to one of his sisters? Problem 31. The pedigree that follows indicates the occurrence of albinism in a group of Hopi Indians, among whom the trait is unusually frequent. Assume that the trait is fully penetrant (all individuals with a genotype that could give rise to albinism will display this condition). a. Is albinism in this population caused by a recessive or a dominant allele? b. Is the gene sex-linked or autosomal? What are the genotypes of the following individuals? c. individual I-I d. individual 1-8 e. individual 1-9 f. individual II-6 g. individual II-8 h. individual III-4 3 P a g e B I O S p r i n g

4 Problem #37. Several different antigens can be detected in blood tests. The following four traits were tested for each individual shown: ABO type (I A and I B codominant, i recessive) Rh type (Rh + dominant to Rh - ) MN type (M and N codominant) Xg (a) type (Xg (a+) dominant to Xg (a-) All of these blood type genes are autosomal, except for Xg (a), which is X linked. Mother AB RH - MN Xg(a+) Daughter A RH + MN Xg(a-) Alleged father 1 AB RH+ M Xg(a+) Alleged father 2 Alleged father 3 A B RH- N Xg(a-) RH+ N Xg(a-) Alleged father 4 o RH- MN Xg(a-) a. Which, if any, of the alleged fathers could be the real father? b. Would your answer to part a change if the daughter had Turner syndrome (the abnormal phenotype seen in XO individuals)? If so, how? Problem #41. The pedigree at the bottom of the page shows the inheritance of various types of cancer in a particular family. Molecular analysis (described in subsequent chapters) indicate that with one exception, the cancers occurring in the patients in this pedigree are associated with a rare mutation in a gene called BRCA2. Which individual is the exceptional cancer patient whose disease is not associated with a BRCA2 mutation? Is the BRCA2 mutation dominant or recessive to the normal BRCA2 allele in terms of its cancer-causing effects? Is the BRCA2 gene likely to reside on the X chromosome, the Y chromosome, or an autosome? How definitive is your assignment of the chromosome carrying BRCA2? Is the penetrance of the cancer phenotype complete or incomplete? Is the expressivity of the cancer phenotype unvarying or variable? 4 P a g e B I O S p r i n g

5 Are any of the cancer phenotypes associated with the BRCA2 mutation sex-limited or sex-influenced? How can you explain the absence of individuals diagnosed with cancer in generations I and II? Problem #8. In Drosophila, males from a true-breeding stock with raspberry-colored eyes were mated to females from a true-breeding stock with sable-colored bodies. In the F 1 generation, all the females had wild-type eye and body color, while all the males had wild-type eye color but sable-colored bodies. When F 1 males and females are mated, the F 2 generation was composed of 216 females with wild type eyes and bodies, 223 females with wild-type eyes and sable-bodies, 191 males with wild-type eyes and sable-bodies, 188 males with raspberry eyes and wild-type bodies, 23 males with wild-type eyes and bodies, and 27 males with raspberry eyes and sable bodies. Explain these results by diagraming crosses, and calculate any relevant map distances. Problem # 14. In corn, the allele A allows the deposition of anthocynanin (blue) pigment in the kernels (seeds), while aa plants have yellow kernels. At a second gene, W- produces smooth kernels, while ww kernels are wrinkled. A plant with blue smooth kernels was crossed to a plant with yellow wrinkled kernels. The progeny consisted of 1447 blue smooth, 169 blue wrinkled, 186 yellow smooth, and 1510 yellow wrinkled. a. Perform a Chi Square analysis of data. b. Are the a and w loci linked? If so how far apart are they? c. What was the genotype of the blue smooth parent? Include the chromosome arrangement of alleles. d. If a plant grown from a blue wrinkled progeny seed is crossed to a plant grown from a yellow smooth F 1 seed, what kinds of kernels would be expected and in what proportions? 5 P a g e B I O S p r i n g

6 Problem # 24. In the tubular flowers of foxgloves, wild-type coloration is red while a mutation called white produces white flowers. Another mutation, called peloria, causes the flowers at the apex of the stem to be huge. Yet another mutation called dwarf, affects the stem length. You cross a white-flowered plant (otherwise phenotypically wild type) to a plant that is dwarf and peloria but has wild type red flower color. All of the F 1 plants are tall with white normal-sized flowers. You cross an F1 plant back to the dwarf and peloria parent, and you see 543 progeny shown in the chart. (only mutants traits are noted.) dwarf, peloria 172 white 162 dwarf, peloria, white 56 wild type 48 dwarf, white 51 peloria 43 dwarf 6 peloria, white 5 a. Which alleles are dominant? b. What were the genotypes of the parents in the original cross? c. Perform a Chi Square analysis to determine if linkage is present d. Draw a map showing the linkage relationships of these three loci? e. Is there interference? If so, calculate the coefficient of coincidence and the interference values. Problem #33. Neurospora of genotype a + c are crossed with Neurospora of genotype + b +. The following tetrads are obtained (note the genotype of the four spore pairs in an ascus are listed, rather than listing all eight spores): a + c a b c + + c + b c a b + a + c a + c a b c a + c a b c a b + a b c + b b c b a b + a c + b a. In how many cells has meiosis occurred to yield these data? b. Give the best genetic map to explain these results. Indicate all relevant genetic distances, both between genes and between each gene and its respective centromere. c. Diagram a meiosis that could give rise to one of the three tetrads in the class at the far right in the list. 6 P a g e B I O S p r i n g