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General Genetics 2005 Exam 1 (60 points) Name __________________________________ Multiple Choice. (1 point each) _____During interphase of the cell cycle ___. A. B. C. D. E. DNA recombines Sister chromatids move to opposite poles The nuclear membrane disappears RNA replicates DNA content essentially doubles _____In dihybrid crosses, the ratio 9:3:3:1 indicates ___. A. Segregation of alleles B. Independent assortment C. Intermediate dominance D. Three alleles for each trait _____Phenotype is to protein as genotype is to A. Genotype B. DNA C. Expressivity D. RNA E. Mutation _____An allele is ___. A. B. C. D. E. one of the bases in DNA an alternate form of a gene another term for epistasis present only in males and is responsible for sex determination found in mitochondria but not in nuclei _____Chromosomes that are matched up or paired at metaphase of meiosis I are called ___? A. B. C. D. E. homologous heterologous complementary non-disjunctive parallel _____Albinism, lack of pigmentation in humans, results from an autosomal recessive gene designated a. Two parents with normal pigmentation have an albino child. What is the probability that their next child will have normal pigmentation? What is the probability that the next child will be an albino girl? A. B. C. D. E. ¼; 1/8 3/4, ¼ ¼; ½ 3/4, 1/8 1/8; ¼ _____ The probability that all five children in a family will be males is A. B. C. D. E. 1/32 1/16 1/2 5/16 5/32 _____What ratios typically result from crosses dealing with two genes? A. B. C. D. E. 9:3:3:1, 1:1:1:1 1:1:1:1, 1:4:6:4:1 3:1, 1:1, 1:2:1 9:7, 12:3:1 15:1, 1:2 _____ Individuals whose genotype is represented by the alleles Aa are described genotypically as A. B. C. D. E. heterozygous dihybrid homozygous homologous dominant _____ Which of the following processes occurs in meiosis but not mitosis? A. B. C. D. Cell division Separation of homologous chromosomes to opposite poles Chromatic formation Chromosome condensation (shortening) _____ The end result of meiosis is A. B. C. D. two cells with the exact same chromosome complement of the starting cell two cells with half the chromosome complement of the starting cell four cells with the exact same chromosome complement of the starting cell four cells with half the chromosome complement of the starting cell _____ An individual that always produces offspring with a specific phenotype is described as A. B. C. D. true-breading wild-type polymorphic boring _____ To determine if an organism with a dominant phenotype is heterozygous, one can perform a ___. A. B. C. D. reciprocal cross monohybrid cross didhybrid cross testcross Short Answer. (variable points) Name one human genetic disorder that is inherited in a simple Mendelian pattern (2 points) What is the purpose of “check points” during interphase of the cell cycle? (2 points) Purple flower color in peas is dominant to white. Assume that Mendel conducted a series of experiments where plants with purple flowers were crossed with plants with white flowers and the following progeny were produced: 325 purple flowers and 350 white flowers. What is the most probable genotype of each parent? (2 points) Describe one process that occurs during meiosis that is responsible for creating genetic diversity within a population. (1 point) One form of deafness in humans can be caused by a rare autosomal dominant gene. In a mating involving a deaf man and a deaf woman, could all the children have normal hearing? Explain. (2 point) Calculate the probability of having two girls and two boys in a family with four children. (2 point) What is the probability of having 6 girls and two boys in a family with the following birth order: BGGGGBGG? (1 points) Phenylketonuria (PKU) is a recessive trait which results in toxicity due to incomplete metabolism of phenylalanine. The PKU trait is due to the absence of an enzyme responsible for metabolism of phenylaline. Two parents without PKU have a child with PKU. What is the probability that their next child will have PKU? What is the probability of the couple having two additional children, both of which do not have PKU? (2 points) Draw a Punnet square for the following cross: GgLl x GgLl and circle the genotypes that will produce individuals who have both dominant phenotypes. (6 points) A breed of guinea pigs can have either black and white coloration or brown and white coloration. For each of the crosses given below, write the most probable genotype (or genotypes if more than one answer is possible) for the PARENTS. (3 points) Parental phenotypes Phenotypes of Offspring Black and white Brown and white A) black and white x brown and white B) black and white x brown and white C) black and white x black and white Cross A 12 29 19 Cross B 14 0 7 Cross C In ReBop genetics the symbol Q is for curly tails and q is for straight tails, B is for a 3 body segments and b is for 2 body segments. In a cross between two ReBops with Curly tails and 3 body segments and both with the genotypes QqBb what fraction of the ReBops will have: A) Curly tails and 2 body segments (1 point) B) 2 body segments (1 point) C) Straight tails and 3 body segments (1 point) D) Curly tails (1 point) E) Straight tails and 2 body segments (1 point) F) Curly tails and 3 body segments (1 point) The following diagram shows chromosomes in either anaphase of mitosis or anaphase I or II of meiosis. The organism has a diploid number of (2n=4). In other words it has two copies of two different chromosomes (A,a and B,b). Cross out those chromosome arrangements that are not possible (ignoring crossing over) and for those that are possible, indicate which stage of mitosis or meiosis is represented. (4 points) A. . B. .. C. . D. . When possible (specify if it is not possible), give the stages of mitosis and meiosis I or II at which: (4 points) Stage of Mitosis Stage of Meiosis Event _______________ _______________ Homologous replicated chromosomes (sister chromatids) move toward opposite poles of the cell _______________ _______________ Centromeres align at the equator in diploid cells. _______________ _______________ Homologous chromosomes pair up _______________ _______________ Unpaired chromosomes congregate at the equator of the spindle Assume that a certain organism has a diploid number of 2 pairs of chromosomes (2n=4) in its body cells and that these chromosomes may be referred to as the A, a chromosomes and the B, b chromosomes. Identify, from the choices given below, the stage of mitotic or meiotic cell division for each diagram. (6 points) Choices: (each may be used more than once or not at all) A. B. C. D. E. F. Interphase Anaphase of mitosis Metaphase of mitosis Anaphase I or meiosis Anaphase II of meiosis Metaphase II of meiosis The diagram below depicts the pedigree of a family along with the molecular analysis of the gene associated with a specific disorder with which individual II-3 was afflicted. Fill in the DNA banding pattern for individuals II-3 and I-2. Indicate the genotypes for individuals II-1 and II-2. (4 points) Genotype II-1 II-2 BONUS Explain how genes on two different pairs of homologous chromosomes with different alleles (A, a and B, b) go through the process of meiosis (you may use diagrams). (5 points)