exam 1 a

exam 1 a - MCB 200 Name Fall 2007 Exam IA Section Answer...

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Unformatted text preview: MCB 200 Name Fall 2007 Exam IA Section Answer Key 1. +2 function +1 recognition What is the primary function of the tRNA molecule and by what recognition feature is this function accomplished? (3pts) Translates an mRNA codon into an amino acid during protein synthesis via recognition with a complementary anticodon If 33% of the nucleotide bases in a duplex DNA sample are found to be thymine, What percentage of the bases are cytosine? (2pts) 33% T = 33% A -> 66% A+T 100% - 66% = 34% C + G 34%/2 = 17% C If the sequence of one strand of DNA is 5'- A C G C T A G A A -3', What is the sequence of the corresponding RNA, transcribed using this strand as a template? Label the 5’ and 3’ ends. (3pts) 3’-UGCGAUCUU-5’ +2 sequence or +1 labeling 4. +2 nucleosome 5’-UUCUAGCGU-3’ What is the basic structural unit of chromatin and what is the major class of proteins responsible for this structure? (3pts) Nucleosomes composed of histone proteins +1 histones 5. Common red- green color blindness is an X-linked recessive trait. A man with normal vision marries a woman who has normal Vision, but whose father is color blind. What is the probability that they will have a son who is color blind? (3pts) 1/2 XY x 1/2 colorblindness allele = 1/4 What is the process of cell division that ensures each of the two daughter cells receives a chromosome complement identical with the complement of the parent cell? (2pts) Mitosis What are the longitudinal halves of a chromosome that have undergone replication called? (2pts) Sister chromatids At what stage of meiosis do bivalents become aligned on the metaphase plate? (2pts) Metaphase of Meiosis I 10. 11. 12. 13. 14. Printed Last Name What is the probability that all children in a four-children family will be males? (3pts) 1/2 x 1/2 x 1/2 x 1/2 = (1/2)4 or 1/16 What types of chromosomes pair in meiosis and have the same genetic loci and structure? (2pts) Homologous chromosomes If the recombination frequency between two genes is 1.5 percent, what is the genetic distance between the two genes in map units on a linkage map? (2pts) 1.5 Centimorgans (cM) What designation is given to genes which do not undergo independent assortment but are transmitted together? (2pts) Linked What is the physical exchange of segments between homologous chromosomes? (2pts) Recombination or Crossing Over Mendel studies seven different loci in peas, with two alleles possible for each locus. Let the symbol for tall be T and short be t and let the symbol for green pods be G and yellow pods be g. Write the symbols for each of the following genotypes: (12pts) a) a homozygous tall plant: TT b) a plant heterozygous for pod color: Gg c) a short plant with yellow pods: ttgg d) a plant heterozygous at both loci: TtGg e) a gamete with the tall allele: T l) a gamete with short and green alleles: tG Printed Last Name 15. A man’s wife has an albino child. Albinism, a lack of melanin pigment, is caused by the recessive allele of a single gene. “Neither you nor I is albino”, said the man. “Therefore, I am not the father of this child.” Is the man correct? Explain your reasoning. (4pts) +2 answer No. Both parents may be heterozygous carriers for the albinism +2 reason allele, thus having a 25% (1/4) chance of producing an albino child. 16. Write all the kinds of gametes that can be produced by a person with this genotype: Aa BB cc Dd. (4pts) ABcD +1 each ABcd chD chd 17. You are a scientist studying several families that have members who appear to be resistant to infection by Asian Bird Flu. Several of these family members also have dimpled chins. Both of these traits are inherited as autosomal dominant conditions. In the following pedigree notice that the maternal grandmother is both resistant to infection (shaded) and has a dimpled chin (D), and that these two traits appear to be linked. a) Circle all progeny displaying recombination between these traits. (2pts) b) Based on this pedigree calculate the genetic distance between the chin dimpling gene, and the gene conferring resistance to bird flu infection. (4pts) +2 answer 2/10 = 0.2 = 20% = 20 cM +2 work Printed Last Name 18. The A and B alleles for blood type are codominant to the recessive 0 allele. In a paternity case, the mother and the child both have blood type 0. The alleged father claims he is not the parent of the child and attempts to prove his casing by taking a blood test that reveals that he is blood type A. +1 answer +2 reason b) +1 answer +2 reason +1 answer +2 reason II III IV Is knowing the blood type of the alleged father (individual III-1) sufficient to exclude him as the parent of the child? Explain your answer using the appropriate genotypes. (3pts) No. The alleged father may be a carrier for the 0 allele (Ai). The alleged father's mother (individual 11-1) is blood type A and his father (11-2) is blood type AB. Is this information sufficient to exclude him? Explain your answers using the appropriate genotypes. (3pts) No. The alleged father’s mother may also be a carrier for the 0 allele (Ai). The alleged father's maternal grandparents (individuals I-1 and I-2) are both blood type AB. Does this additional family data allow him to be excluded? Explain your answers using the appropriate genotypes. (3pts) Yes. Since both of the alleged father’s maternal grandparents are blood type AB, this makes both his mother and himself homozygous for blood type A (AA), thus excluding him as the parent. Printed Last Name 19. Free earlobes are determined by the autosomal dominant allele E, and attached earlobes are determined by homozygosity for the recessive allele e. If a person who is heterozygous for free earlobes marries a person who has attached earlobes: a) What is the probability that they will have three children with attached earlobes? (4pts) Show your work for the genetic cross to obtain full credit. 11/2 [3 or 1/8 +2 answer +2 work Ee x ee -> 1/2 Ee 1/2 ee (attached earlobes) 1/2 x 1/2 x 1/2 = (1/2)3 or 1/8 b) What is the probability that they will have first a boy with attached earlobes, followed by a girl who has free earlobes? (4pts) Show your work for the genetic cross to obtain full credit. 11/412 or 1/ 16 +2 answer +2 work XX x XY ->1/2 XX 1/2 XY 1/2 XY x 1/2 ee = 1/4 XYee 1/2XX x 1/2 Ee = 1/4 XXEe 1/4 x 1/4 = (1/4)2 or 1/16 0) Based on Mendel’s law, what is the process by which alleles of a gene pair separate during gametogenesis? (2pts) Segregation d) If two genes are unlinked, which of Mendel’s laws applies during Meiosis? (2pts) Independent Assortment 20. Printed Last Name It is known that obesity in humans is controlled by the action of multiple genes. Obesity phenotypes are also influenced by environmental factors, such as a westernized diet and overeating, making this an example of a (a) multifactorial trait. (2pts) Recent molecular genetic studies have identified twelve candidate genes on different autosomes that are likely involved in obesity. It is important to know that they are on different chromosomes, indicating that the alleles for these genes will assort independently. Under this model of 12 genes, each person has (b) 24 alleles that determine obesity pathogenesis. (2pts) Although it is likely to be more complicated, we will assume that alleles at each of these genes act in simple additive fashion with “dominant or active” alleles adding one unit to the pathological phenotype, and “recessive or neutral” alleles contributing to a wild-type phenotype. Under this same model, (c) 25 would exist. (2pts) different possible phenotypes for obesity ((1) What is the probability that two persons who are both heterozygous for all of these genes will have a child who is also heterozygous at each of the candidate gene loci? Show your work to obtain full credit. (4pts) 11/2)12 or 1/4096 +2 answer +2 work Aa X Aa -> 1/4 AA 1/2 Aa 1/4 aa 1/2 X 1/2 X 1/2 X 1/2 X 1/2 X 1/2 X 1/2 X 1/2 X 1/2 X 1/2 X 1/2 X 1/2 = (1/2)12 or 1/4096 Printed Last Name 21. Consider a hypothetical diploid genome (N=2) with two pairs of chromosomes. For each of the following diagrams (a—f), identify the cycle as mitosis (M), meiosis 1 (M1), or meiosis 11 (M11), and identify the stage as prophase, metaphase, anaphase, or telophase. (12pts) +2 each (+1 cycle and +1 stage) b) MI Meta hase // c) MII Prophase (1) M11 Anaghase .1 f 1 Ad? "4. i ", DJ): I ‘\ e) MI Pro 'hase t) M Metaphase ...
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This test prep was uploaded on 04/04/2008 for the course MCB 200 taught by Professor Ovtchinnikov during the Spring '08 term at UConn.

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exam 1 a - MCB 200 Name Fall 2007 Exam IA Section Answer...

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