Science Genetics
NAME_______________________ TA:__________________ Section #________ INSTRUCTIONS: 1. Write your answers on the paper, and hand in the assignment at the end of the test. 2. If you need extra space for calculations, write them on the back of the sheet. 3. Read the questions CAREFULLY; jargon can often be confusing. 4. Pace yourself. Question 1. Complete the following table to compare the behaviour of chromosomes during mitosis and meiosis. In the mitosis column, just indicate Yes or No as to whether the event occurs in mitosis. For the meiosis column, also indicate if the event occurs in meiosis I or meiosis II. Event Mitosis Meiosis a. Chromosomes line up at the equator b. Homologous chromosomes separate c. Sister chromatids separate d. Produces identical daughter cell e. Recombination occurs (10 points) Question 2. Using different colors to distinguish chromosomes of maternal and paternal origin, draw a telocentric set of homologous chromosomes at: a. Prophase I after a single crossover between two of the non-sister chromatids. b. Anaphase I (make sure you include the results of the crossover described above). c. Anaphase II (draw all cells and make sure you include the crossover results). 12 points (22 so far) Copyright 2022 Richard Cripps, Kumar Vishal Page 1 Question 3. For the phenotypic ratios on the left (a-e), indicate to which of the genetic relationships described on the right (1-5) they correspond. Provide your answers by writing the numbers 1-5 in the left column. a. 1:2 1. Monohybrid inheritance where the alleles show incomplete dominance. b. 1:2:1 2. Testcross of a tall, purple-flowered, round-seeded pea plant c. 9:3:4 3. Monohybrid inheritance for a lethal mutation d. 1:1:1:1 4. A dihybrid cross including epistasis e. 1:1:1:1:1:1:1:1 5. A possible offspring phenotypic ratio when a person of A blood type is crossed to a person of B blood type. (10 points) Question 4. a. What is a Barr body? The existence of Barr bodies in four humans was analyzed, and images of a nucleus from each patient is shown below. b. Based upon what you know about sex determination in humans, what would you predict to be the sex of each individual? For which individual would you be unsure of the sex, and suspect a chromosomal abnormality? A B C D Karyotypes of each person were also generated, however a careless doctor dropped the slides on the floor and they became muddled, so it was not clear from which individual which karyotype arose. The sex chromosome karyotypes of the four individuals were: XX, XY, XXX, and XXY. c. If individual C is phenotypically male, match up the sex chromosome karyotypes with the individuals (A-D). A B (18 points)(50) C D Copyright 2022 Richard Cripps, Kumar Vishal Page 2 Question 5. The table below shows the results of microsatellite analysis of a fetus and the two parents. a. What genetic condition does the fetus show? b. From which parent did the extra genetic material originate? c. What are the likely mechanisms by which the extra genetic material occurred (provide two possible mechanisms). d. Which pair of microsatellite markers are linked? Markers Chromosome locations TPOX 2p23-pter D2S1338 2q35-37.1 D3S1358 3p21 FGA 4q28 D5S818 5q21-31 D7S820 7q11.21-22 TH01 11p15.5 vWA 12p12-pter D13S317 13q22-31 D16S539 16q24-qter D18S51 18q21.33 D19S433 19q12-13.1 D21S11 21q21 (8 points)(58) Genotypes Father Mother Fetus 13 23 123 14 23 124 12 33 123 12 11 112 11 23 113 22 12 122 33 12 233 12 11 122 13 23 133 12 12 222 24 13 234 23 14 234 12 23 223 Question 6. In a maternity ward, four babies become accidentally mixed up. The babies were bloodtyped and found to have the following types: O, A, B, and AB. The parents were also typed and found to have the following types: (a) AB x O (b) A x O (c) A x AB (d) O x O Indicate which parents had which baby, and the genotypes of the parents and the baby for each cross. (8 points)(66) Copyright 2022 Richard Cripps, Kumar Vishal Page 3 Question 7. The following human pedigree describes the distribution of the inability to taste the chemical phenylthiocarbamide (PTC) – shaded individuals cannot taste the chemical. This phenotype is quite common, therefore individuals from outside the family are sometimes carriers. a. State, with reasoning, whether the inability to taste PTC is autosomal or sex-linked, and recessive or dominant. b. What are the possible genotypes of the following individuals (make sure that you indicate all of the possible genotypes): I, 1 III, 1 III, 2 IV, 2 c. If individual II,4 is homozygous, what is the genotype of II,3 ? (10 points)(76) Question 8. Vestigial wings in Drosophila is caused by a recessive mutation in a gene called vestigial (vg). A purple eye color also results from a linked recessive mutation in a different gene named pr. A female Drosophila, that was heterozygous for each of these mutations was crossed to a male that was homozygous for the recessive allele at each gene. I obtained the following offspring phenotypes: Vestigial wings, purple eyes Normal wings, normal (red) eyes Normal wings, purple eyes Vestigial wings, normal eyes 435 445 55 65 TOTAL 1000 a. Calculate the recombination frequency between the two genes. Show your working. b. Give the genotype of the female parent and draw how the alleles are arranged on each chromosome. c. Was the female fly cis- or trans- heterozygous? (4 points)(80) Copyright 2022 Richard Cripps, Kumar Vishal Page 4
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