Download Problem Set 3 – KEY

Genetics Exam 3 Problem Set Complete this problem set to supplement your review! Note: I do not have access to your test questions, so there is no guarantee this will be a reflection of the questions you’ll encounter on your exam. It is intended as a way to test your knowledge on the topics. Additionally, please remember that your SI Leader created this, not your professor; thus, you are welcome to let me know if you feel there are any errors. Review your professor’s lecture questions + the textbook problems for every chapter! Chapter 25 – Population Genetics 1. In pea plants, purple flower color, represented by P, is dominant to white flower color, represented by p. In a population of pea plants there are the following plants: Genotype Number PP 128 Pp 113 pp 89 a. Calculate the genotypic frequencies for each genotype. f(PP) = 128/330 = 0.388; f(Pp) = 113/330 = 0.342; f(pp) = 89/300 = 0.270
b. Calculate the allelic frequencies. f(P) = 0.559; f(p) = 0.441
2. In a population at Hardy-­‐Weinberg equilibrium, F is the dominant allele and f is the recessive allele for a trait. Out of a population of 80, 15 are homozygous recessive. a. Determine the frequency of the recessive allele, f. q = 0.433
b. Determine the frequency of the dominant allele, F. p = 0.567
c. Determine the frequency of each genotype. f(FF) = p2 = 0.321; f(Ff) = 2pq = 0.491; f(ff) = q2 = 0.188
Chapter 10 – Chemical Nature of the Gene 1. Chargaff’s Rule states that: a. The proportion of guanine is equal to the proportion of adenine. b. The proportion of pyrimidines is equal to the proportion of purines. c. The proportion of adenine is equal to the proportion of thymine. d. The proportion of adenine is equal to the proportion of cytosine. e. The proportion of guanine is equal to the proportion of thymine. 2. Which of the following is not a feature of the structure of DNA? a. Hexose sugar Note: Ribose/deoxyribose are PENTOSE sugars b. Nitrogenous base c. Phosphodiester linkage d. Covalent bonding e. Hydrogen bonding 3. Give two structural differences between DNA and RNA. Possible answers: Different sugars (deoxyribose/ribose); different bases (thymine/uracil); double-­‐stranded versus single-­‐stranded 4. Which of the following statements is correct regarding some of the structures found in DNA and RNA? NOTE: THIS QUESTION HAS BEEN CORRECTED. a. Ribose contains an 2’ OH group while deoxyribose does not, and purines have a double-­‐ring structure while pyrimidines have a single-­‐ring structure. b. Both ribose and deoxyribose contain 2’ OH groups, and purines have a double-­‐
ring structure while pyrimidines have a single-­‐ring structure. c. Ribose contains a 2’ OH group while deoxyribose does not, and purines have a single-­‐ring structure while pyrimidines have a double-­‐ring structure. d. Ribose does not contain a 2’ OH group while deoxyribose does, and purines have a double-­‐ring structure while pyrimidines have a single-­‐ring structure. e. Ribose does not contain a 2’ OH group while deoxyribose does, and purines have a single-­‐ring structure while pyrimidines have a double-­‐ring structure. Chapter 12 – Transcription 1. What is the function of topoisomerase? a. DNA methylation b. Assisting the assembly of intrinsic factors at the site of transcription c. Unzipping the DNA double helix d. Loosening tension in the double helix ahead of helicase e. Charging tRNA molecules with amino acids 2. Which of the following statements is correct regarding eukaryotic DNA replication? a. Only new strands on the leading strand are synthesized in the same direction as the movement of the replication fork. b. Both new strands are synthesized in the direction of the replication fork. c. There is only one origin of replication, just like in bacteria. d. DNA is synthesized in the 5’ to 3’ direction on the lagging strand, but the 3’ to 5’ direction on the leading strand. e. The lagging strand is also known as the sense strand. 3. Which enzyme involved in DNA replication has proofreading capabilities? a. DNA polymerase I BOTH ARE CORRECT – SEE SLIDE 32 OF CHAPTER 12 b. DNA polymerase III c. Ligase d. Primase e. Gyrase 4. Complete the table below, providing the enzyme and its function(s). Enzyme Primase Helicase Function(s) Inserts RNA primers Unzips DNA helix Gyrase/topoisomerase DNA polymerase III DNA polymerase I Ligase Loosens tension in helix ahead of helicase Synthesizes DNA by attaching nucleotides to the 3’ end of a RNA primer Replaces RNA primers with DNA nucleotides Creates a phosphodiester bond between Okazaki fragments (‘seals nicks’) 5. Which of the following statements is correct about the three proposed models of DNA replication? a. Conservative replication is currently the most accepted model. b. After the second round of replication, under the dispersive model, half of the molecules will be entirely new DNA. c. After the second round of replication, under the semiconservative model, half of the DNA molecules will be entirely new DNA. d. The semiconservative model suggests that pieces of the old DNA double helix recombine with newly synthesized DNA to form new DNA molecules. e. After the second round of replication, under the conservative model, all of the DNA molecules have both new and old DNA. 6. Initiator proteins during replication use what to identify the origin of replication? a. The shape of the chromosome b. A specific consensus sequence c. Specific binding proteins already present at the origin d. A gap in the nucleotide sequence e. Nothing; they bind at random to create an origin 7. Which of the following statements is not true regarding DNA polymerase I and III? a. Neither is capable of initiating the synthesis of a new strand of DNA. b. Both synthesize in the 5’ to 3’ direction. c. Both possess proofreading activities. d. Both have exonuclease activity in the 3’ to 5’ direction. e. Both have exonuclease activity in the 5’ to 3’ direction. ONLY I DOES 8. Which enzyme joins Okazaki fragments together? a. DNA polymerase III b. Ligase c. DNA polymerase I d. Primase e. Topoisomerase 9. DNA polymerases can add new DNA nucleotides: a. Directly onto existing DNA without a primer. b. Directly onto existing RNA without a primer. c. Onto the 5’ end of an RNA primer. d. Onto the 3’ end of an RNA primer. e. Between the nicks in the sugar-­‐phosphate backbone. 10. DNA replication is: a. Unidirectional, occuring on only one strand. b. Unidirectional, occuring on both strands. c. Bidirectional, occuring on only one strand. d. Bidirectional, occuring on both strands. e. Either unidirectional or bidirectional, occuring on one or both strands.