Test Bank for iGenetics: A Molecular Approach, 3rd Edition

iGenetics: A Molecular Approach, 3e (Russell/Bose) Chapter 2 DNA: The Genetic Material MATCHING Please select the best match for each term. A) The basic structural unit of chromatin with “bead-on-a-string” morphology B) The region of a eukaryotic chromosome found near the attachment point of mitotic or meiotic spindle fibers C) A DNA molecule and associated proteins D) The constituent monomer of DNA and RNA E) The region of a prokaryotic cell where the chromosome is located 1) Centromere Skill: Factual recall 2) Nucleoid Skill: Factual recall 3) Nucleotide Skill: Factual recall 4) Chromosome Skill: Factual recall 5) Nucleosome Skill: Factual recall Answers: 1) B 2) E 3) D 4) C 5) A 1 Copyright © 2010 Pearson Education, Inc. MULTIPLE CHOICE 6) Loosely aggregated DNA bound to proteins in a eukaryotic cell is called A) chromosomes. B) chromatin. C) chromatid. D) centromere. E) nucleoid. Answer: B Skill: Factual recall 7) The C-value is the amount of DNA in a A) haploid genome. B) diploid genome. C) bacterial genome. D) eukaryotic genome. E) cell’s nucleus. Answer: A Skill: Factual recall 8) The chromosome of most prokaryotes differs from those of eukaryotes in that A) the prokaryotic chromosome is linear, while the eukaryotic chromosome is circular. B) the prokaryotic chromosome is circular, while the eukaryotic chromosome is linear. C) the prokaryotic chromosome does not replicate before mitosis, while the eukaryotic chromosome does. D) the prokaryotic chromosome does not contain genes, while the eukaryotic chromosome does. E) the prokaryotic chromosome is not necessary for the organism’s survival, while the eukaryotic chromosome is. Answer: B Skill: Factual recall 9) A Barr body is an example of A) constitutive euchromatin. B) facultative euchromatin. C) facultative heterochromatin. D) a nucleosome. E) constitutive heterochromatin. Answer: C Skill: Factual recall 10) The definition of transformation is A) the shift of genetic information from DNA to protein. B) the genetic alteration of an organism. C) the uptake of genetic information by a cell from the environment. D) Both B and C E) None of these Answer: D Skill: Factual recall 2 Copyright © 2010 Pearson Education, Inc. 11) In Griffith’s experiment involving the transformation of Streptococcus pneumoniae, A) the R strain was virulent. B) the S strain was virulent. C) both the R and S strains were virulent. D) the R strain had a protein capsule. E) the S strain had a protein capsule. Answer: B Skill: Factual recall 12) What was the transforming principle isolated in Griffith’s experiment? A) Protein B) RNA C) DNA D) Virus E) Polysaccharide Answer: C Skill: Factual recall 13) Who used radioactively labeled T2 bacteriophage to confirm the identity of the transforming principle? A) Griffith B) Hershey and Chase C) Avery D) Gierer and Schramm E) Beadle and Tatum Answer: B Skill: Factual recall 14) Which part of the T2 bacteriophage entered E. coli cells in the experiment which confirmed the identity of the transforming principle? A) The RNA B) The DNA C) The whole virus D) The protein coat E) No part Answer: B Skill: Factual recall 15) Certain ________ have RNA for their genetic material. A) bacteria B) viruses C) plants D) eukaryotes E) prokaryotes Answer: B Skill: Factual recall 3 Copyright © 2010 Pearson Education, Inc. 16) What did the X-ray diffraction patterns initially reveal about the DNA molecule? A) It is of uniform diameter and has a helical structure. B) It is a helical molecule with paired bases in the center. C) It is double-stranded with antiparallel strands. D) It is acidic, phosphorus-rich, and large. E) It contains hereditary information. Answer: A Skill: Factual recall 17) What did Watson and Crick deduce about the three-dimensional structure of DNA? A) There is a repeating pattern every 3.4 nm and every 0.34 nm. B) It is a double-stranded helix. C) It contains a lot of phosphorus. D) It is a large molecule. E) It consists of supercoiled chromatin. Answer: B Skill: Factual recall 18) Which of the following is a nonhistone protein found in chromatin? A) H1 B) HMG C) H2A D) H5 E) All of these Answer: B Skill: Factual recall 19) Antiparallel means that A) the two polynucleotide chains run in opposite directions. B) each DNA molecule consists of one old and one new strand. C) opposite strands are held together by base pairing. D) the helix twists to the right. E) there is complementary base-pairing. Answer: A Skill: Factual recall 20) Complementary base-pairing allows for A) spontaneous mutations to occur. B) genes to be expressed as a phenotype. C) DNA to serve as its own template for replication. D) replication to be semiconservative. E) covalent bonds to form between the opposite bases. Answer: C Skill: Factual recall 4 Copyright © 2010 Pearson Education, Inc. 21) Which of the following are the purine nucleotides in DNA? A) Adenine and thymine B) Cytosine and guanine C) Adenine and cytosine D) Guanine and adenine E) Thymine and uracil Answer: D Skill: Factual recall 22) Topoisomerases function to A) remove nucleotides from DNA. B) join DNA pieces together. C) twist DNA molecules. D) attach DNA loops to scaffold proteins. E) move chromosomes along spindle fibers. Answer: C Skill: Factual recall 23) Which form of DNA is a left-handed double helix? A) A-DNA B) B-DNA C) L-DNA D) R-DNA E) Z-DNA Answer: E Skill: Factual recall 24) The displacement loop (D-loop) may be a characteristic of A) centromeres. B) telomeres. C) A-DNA. D) B-DNA. E) Z-DNA. Answer: B Skill: Factual recall 25) Which nucleotide is absent in RNA? A) Adenine B) Guanine C) Uracil D) Cytosine E) Thymine Answer: E Skill: Factual recall 5 Copyright © 2010 Pearson Education, Inc. TRUE/FALSE 26) DNA and RNA both contain phosphate and ribose. Answer: FALSE Explanation: They both contain phosphate, but DNA contains the sugar deoxyribose rather than ribose. Skill: Factual recall 27) Hershey and Chase used radioactive sulfur to label the genetic material of bacteriophages. Answer: FALSE Explanation: The radioactive sulfur labeled the protein coat. Skill: Factual recall 28) In a strand of DNA, a hydrogen bond connects the phosphate group of one nucleotide to the sugar of the adjacent nucleotide. Answer: FALSE Explanation: A covalent phosphodiester bond connects the two adjacent nucleotides. Skill: Factual recall 29) The genome of the T-even family of bacteriophage consists of single-stranded RNA. Answer: FALSE Explanation: It consists of double-stranded DNA. Skill: Factual recall 30) Borrelia burgdorferi is a bacterium whose genome consists of one large and several small linear chromosomes. Answer: TRUE Skill: Factual recall 31) By weight, the amount of DNA in chromatin is less than that of histone. Answer: FALSE Explanation: The weights of DNA and histone in chromatin are equal. Skill: Factual recall 32) The virus first shown to have RNA as its genetic material was tobacco mosaic virus (TMV). Answer: TRUE Skill: Factual recall 33) The more condensed a part of a chromosome is, the more likely it is that the genes in that region will be active. Answer: FALSE Explanation: The genes in a region are less likely to be active the more condensed a part of a chromosome is. Skill: Factual recall 6 Copyright © 2010 Pearson Education, Inc. 34) The genome of most prokaryotes consists of moderately repetitive DNA. Answer: FALSE Explanation: The genome of most prokaryotes consists of unique-sequence DNA. Skill: Factual recall 35) In eukaryotes, the greatest relative amount of tandemly repeated DNA is associated with centromeres and telomeres. Answer: TRUE Skill: Factual recall SHORT ANSWER 36) In Griffiths’ transformation experiments, under what conditions did the injected mice die? Answer: The mice died when they were injected with living, virulent bacteria, and when they were injected with living, nonvirulent bacteria mixed with heat-killed, virulent bacteria. Skill: Factual recall 37) How could you test whether the transforming ability of a cell extract was due to DNA or RNA? Answer: You could treat the extract with a DNase or RNase enzyme and test whether its transforming ability was intact. Skill: Application of knowledge 38) One of the strands in a DNA double helix has the nucleotide sequence 5′-ACCTGCTACGG3′. What is the sequence of the complementary DNA strand? Answer: 3′-TGGACGATGCC-5′ Skill: Problem-solving 39) What is the function of dispersed repeated sequences such as SINEs and LINEs in eukaryotes? Answer: Little is known about the function of such sequences, but one hypothesis is that they have no function at all. Another is that they are involved in regulating gene expression. Skill: Factual recall 40) What is the C-value paradox, and what is its cause? Answer: There is also no direct relationship between the C-value (the total amount of DNA in the haploid genome) and the structural or organizational complexity of the organism. This is due in part to the amount of repetitive-sequence DNA found in the genome of some organisms. Skill: Conceptual understanding 41) Define Chargaff’s rules of the base composition of DNA. Answer: Chargaff’s rules include the following: (1) the amount of adenine = the amount of thymine, (2) the amount of guanine = the amount of cytosine, and (3) the amount of purines = the amount of pyrimidines. Skill: Factual recall 7 Copyright © 2010 Pearson Education, Inc. 42) Describe the differences between heterochromatin and euchromatin in chromosomes. Are there any situations in which one can be changed into the other? Answer: Euchromatin contains actively transcribed genes and undergoes normal cycles of condensation and decondensation in the cell cycle. Heterochromatin remains condensed and contains genes that are usually transcriptionally inactive. Euchromatin can be inactivated, as in the case of Barr bodies. It is then known as facultative heterochromatin. Skill: Factual recall 43) What are the three necessary characteristics of the hereditary molecule in cells? Answer: (1) It must be able to carry information, (2) it must be able to accurately pass on the information to progeny cells (replicate), and (3) it must be capable of change (evolution). Skill: Conceptual understanding 44) Name the constituent parts of a nucleoside and a nucleotide. Answer: A nucleoside consists of a pentose sugar covalently bonded to a nitrogenous base; a nucleotide is a nucleoside with the addition of a phosphate group. Skill: Factual recall 45) The DNA phage ΦΧ174 was found to have a ratio of bases of 25A:33T:24G:18C. This departs from the usual A/T = 1 and G/C = 1 ratios. How can you explain this? Answer: The genome of the phage consists of single-stranded, rather than double-stranded, DNA. Skill: Conceptual understanding 46) If the human egg has 3 billion base pairs, how many nucleosomes will be present in the nucleus of a human somatic cell? Answer: In humans, the DNA wrapped around each nucleosome is approximately 200 bp (147 bp + 53 bp linker). As such, there will be approximately 3 × 109/2 × 102 = 1.5 × 107 nucleosomes in a human egg nucleus. However, the egg is haploid, whereas the somatic cells are diploid. Therefore, there will be approximately 1.5 × 107 × 2 = 3 × 107 nucleosomes in the nucleus of a human somatic cell. Skill: Problem-solving 47) Why are the amino acid sequences of eukaryotic histones so similar to one another, even among distantly related species? Answer: Evolutionary conservation of these sequences is a strong indicator that histones perform the same basic role in organizing the DNA in the chromosomes of all eukaryotes. Skill: Conceptual understanding 48) Describe the packing of chromatin from the 10-nm to the 30-nm fiber stage. What is the role of histones? Answer: 10-nm chromatin fiber consists of nucleosomes–”beads” of DNA wound around eight core histone proteins–connected by strands of linker DNA. The 30-nm chromatin fiber is created by the binding of histone H1, which brings the linker DNA and the nucleosomes closer together. In the solenoid model of the 30-nm fiber, the nucleosomes are brought together into a spiraling helical structure, with about six nucleosomes per complete turn. Skill: Conceptual understanding 8 Copyright © 2010 Pearson Education, Inc. 49) What is the role of centromeres and telomeres? Answer: Centromeres are the chromosomal regions where mitotic or meiotic spindle fibers attach. They are therefore responsible for the accurate segregation of chromosomes to daughter cells during replication. Telomeres are heterochromatic regions of chromosomes that are also required for replication and stability. They are usually found at the ends of the chromosome and are associated with the nuclear envelope. Skill: Factual recall 50) If the base pairs in a DNA helix are 0.34 nm apart, and a complete (360°) turn of the helix takes 3.4 nm, how many base pairs per turn are there in a DNA molecule? Answer: There are 10 base pairs per turn. Skill: Problem-solving 9 Copyright © 2010 Pearson Education, Inc.