Exam May 2017, answers PDF

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EXAMINATION QUESTION PAPER

Module Code:

BI2S63

Module Title:

Introduction to Genetics

Assessment Sitting:

MAIN

Month Examination to be sat:

MAY

Duration of Examination (in hours and minutes):

2 HOURS

The following items are provided to Candidates:  

Examination answer booklet Supplementary sheets, as detailed below

Instructions to Candidates: Calculators Removal of the examination paper from the venue at the end of the examination Additional Resources (full details detailed below) This paper contains a total of 28 You are required to answer

26

Allowed √

Not Allowed √ √

questions. questions.

Other relevant instructions: You are required to answer all questions of Section A and 2 questions of Section B.

Campus Examination to be sat at:

Treforest

Examination paper version number:

1

Name of Partner College(s) (if applicable)

Page 1 of 9

Section A Question 1 Which enzyme releases tension in DNA during DNA replication? a) DNA polymerase III b) Primase c) Topo isomerase d) Helicase e) DNA polymerase I (1 mark) Question 2 In which phase of mitosis do the sister chromatids disconnect? a) Interphase b) Prophase c) Metaphase d) Anaphase e) Telophase (1 mark) Question 3

Which of the following genotypes would you NOT expect to find among the offspring of a AaBBCc x AabbCc cross? a) b) c) d) e)

AABbCC AaBBcc AaBbCc aaBbCC aaBbcc (1 mark)

Question 4 Which of the following is true about an individual with the genotype PpQQRr a) One of its parents could have had the genotype PPQQRR b) It is homozygous dominant for one character c) It is impossible for it to produce a gamete with genotype pQr d) The Q gene is dominant over both the P and R genes e) If self-crossed, all of its offspring would have the same genotype (1 mark)

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Question 5 When does DNA replication take place during meiosis? DNA replication _____. a) does not take place in cells destined to undergo meiosis b) occurs before Meiosis I begins c) occurs during Prophase I d) occurs between Meiosis I and Meiosis II e) occurs after Telophase II (1 mark)

Question 6 Which is the smallest unit containing the entire human genome? a) All of the DNA in all of the cells of the entire human population b) One human chromosome c) All of the DNA in all of the cells of one human d) One human gamete e) One human somatic cell (1 mark) Question 7 Which process does happen in meiosis but NOT in mitosis? a) Reduction of chromosome number b) DNA replication c) Separation of sister chromatids d) Alignment of chromosomes e) Spindle formation (1 mark) Question 8 If a DNA sample were composed of 10% thymine, what would be the percentage of guanine? a) 10 b) 40 c) 20 d) 80 e) It is impossible to tell from the information given (1 mark)

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Question 9

Identify the lagging strand during duplication of DNA starting from a double helix in the figure above. a) a b) b c) c d) d e) e (1 mark)

Question 10 There are 61 mRNA codons that specify an amino acid, but only 45 tRNAs. This is best explained by the fact that _____. a) the rules for base pairing between the third base of a codon and tRNA are flexible b) many codons are never used, so the tRNAs that recognize them are dispensable c) some tRNAs have anticodons that recognize four or more different codons d) competitive exclusion forces some tRNAs to be destroyed by nucleases e) the DNA codes for all 61 tRNAs, but some are then destroyed (1 mark) Question 11 In negative gene expression control, a gene is switched off when _____. a) lactose is transported into the cell b) a kinase adds a phosphate to DNA c) a regulatory protein is removed from DNA and shuts down transcription d) a regulatory protein binds to DNA and shuts down transcription e) an enzyme destroys the coding DNA (1 mark) Question 12 Which of the following statements about transcription is correct? a) The bacterial RNA holoenzyme is used during the elongation phase of transcription. b) The bacterial promoter lies just downstream of the start site of transcription. c) Sigma factor is needed to recognize the transcriptional termination signal. d) During elongation, the RNA strand is extended in the 5' to 3' direction. e) The extending RNA molecule binds to the sigma factor. (1 mark)

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Question 13 After finding a new medicinal plant, a pharmaceutical company decides to determine if the plant has genes similar to those of other known medicinal plants. To do this, the company annotates the genome of the new plant to _____. a) identify the location of mRNA within the plant cells b) identify genes and determine their functions c) determine what mRNA transcripts are produced d) determine what proteins are produced e) determine whether the plant is resistant to extreme weather events (1 mark)

Question 14 Which of the following evidence most strongly supports the common origin of all life on Earth? All organisms _____. a) show heritable variation b) require energy c)) reproduce d) use essentially the same genetic code e) evolve (1 mark) Question 15 Logically, which of these should cast the most doubt on the relationships depicted by an evolutionary tree? a) Transitional fossils had not been found. b) Relationships between DNA sequences among the species did not match relationships between skeletal patterns. c) None of the organisms depicted by the tree ate the same foods. d) Some of the organisms depicted by the tree had lived in different habitats. e) The skeletal remains of the organisms depicted by the tree were incomplete (in other words, some bones were missing). (1 mark) Question 16 The Dunkers are a religious group that moved from Germany to Pennsylvania in the mid1700s. They do not marry with members outside their own immediate community. Today, the Dunkers are genetically unique and differ in allele frequencies, at many loci, from all other populations including those in their original homeland. Which of the following likely explains the genetic uniqueness of this population? a) Mutation and natural selection b) Sexual selection and inbreeding depression c) Founder effect and genetic drift d) Population bottleneck and Hardy-Weinberg equilibrium e) Heterozygote advantage and stabilizing selection (1 mark)

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Question 17 Which of the following is the most predictable outcome of increased gene flow between two populations? a) Increased genetic difference between the two populations b) Higher average fitness in both populations c) Increased genetic drift d) Decreased genetic difference between the two populations e) Lower average fitness in both populations (1 mark) Question 18 Use the following information to answer the question(s) below. Martin Wikelski and L. Michael Romero (Body size, performance and fitness in Galápagos marine iguanas, Integrative and Comparative Biology 43 [2003]:376-86) measured the snout-to-vent (anus) length of Galápagos marine iguanas and observed the percent survival of different-sized animals, all of the same age. The graph shows the log snout-vent length (SVL, a measure of overall body size) plotted against the percent survival of these different size classes for males and females.

Examine the figure above. What type of selection for body size appears to be occurring in these marine iguanas? a) Disruptive selection b) Stabilizing selection c) Directional selection d) You cannot determine the type of selection from the above information. e) Natural selection does not occur on island populations (1 mark)

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Question 19 Which of the following statements best summarizes evolution by natural selection as it is viewed today? a) Evolution is the descent of humans from the present-day great apes. b) Evolution is the production of adaptations that meet present and anticipated needs. c) Evolution represents the result of selection for acquired characteristics. d) Evolution is the differential survival and reproduction of the most-fit phenotypes. e) Evolution a hierarchical process, with humans at the pinnacle of all life. (1 mark) Question 20 Why isn't inbreeding considered an evolutionary process? a) It does not violate the assumptions of the Hardy-Weinberg Principle. b) It does not change allele frequencies. c) It does not occur often enough to be important in evolution. d) It does not change genotype frequencies. e) Inbreeding does not affect wild populations, only captive ones (1 mark) Question 21 Which species concept(s) would be most useful to a team of biologists conducting a biodiversity survey? a) The Morphological Species concept b) The Phylogenetic Species concept c) The Biological Species concept d) All species concepts would be equally useful. e) None of the above species concepts would be useful. (1 mark)

Question 22 Which mechanism causes postzygotic reproductive isolation? a) Temporal isolation b) Habitat isolation c) Mechanical isolation d) Hybrid sterility e) Incompatible gametes (1 mark) Question 23 Which of the following is an example of polygenic inheritance? a) Pink flowers in snapdragons b) Huntington's disease in humans c) White and purple flower color in peas d) Skin pigmentation in humans e) The ABO blood group in humans

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(1 mark) Question 24 Suppose 64% of a remote mountain village can taste phenylthiocarbamide (PTC) and must, therefore, have at least one copy of the dominant PTC taster allele. If this population conforms to Hardy-Weinberg expectations for this gene, what percentage of the population must be heterozygous for this trait? a) 48% b) 60% c) 32% d) 16% e) 40% (1 mark)

Section B Question 25 Write an essay on DNA replication in prokaryotes. (20 marks) Question 26 Using the Lac operon as an example, describe the regulation of transcription in prokaryotes. (20 marks) Question 27 (a) Determine whether the following two sets of data represent populations that are in HardyWeinberg Equilibrium. Show all of your working. Use the Chi-squared table at the end of this paper to compare observed and expected numbers. Population 1: CCR5 genotypes. In a population of 200 people, the following genotypes are found: 1/1, 120 people; 1/Δ32, 70 people; Δ32/Δ32, 10 people.

Population 2: Sickle-cell haemoglobin. In a population of 400 people, the following genotypes are found: AA, 302 people; AS, 97 people; SS, 1 person.

(14 marks)

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(b) If the recessive trait albinism is present in 1/10,000 individuals in a population at equilibrium, calculate the frequency of: -

the recessive mutant allele

-

the normal dominant allele

-

heterozygotes in the population

(2 marks) (2 marks) (2 marks)

Question 28 Using examples, explain how the process of natural selection works. Include in your answer details of the different types of selection. (20 marks)

CHI Squared table

END OF EXAMINATION

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