Chapter 4 DNA,RNA,and the Flow of Genetic Information Matching Questions Use the following to answer questions 1-10: Choose the correct answer from the list below.Not all of the answers will be used a)annealing b)mRNA molecules c)synonyms d)linear e)amino acid f)Tm g)retroviruses h)exon i)Erwin Chargaff j)release factor k)gene expression 1)Rosalyn Franklin 1 The information-carrying intermediates of translation. Ans:b Section:Introduction 2 The flow of genetic information from DNA to protein is called Ans:k Section:Introduction Scientist who noted the A:T and G:C ratios in DNA are approximately 1:1 Ans:i Section:4.1 4 The temperature at which half the DNA helical character is lost is referred to as Ans:f Section:4.2 5 DNA renaturation after melting is called Ans:a Section:4.2 6 DNA can exist in both circular and forms. Ans:d Section:4.2 Page 1
Page 1 Chapter 4 DNA, RNA, and the Flow of Genetic Information Matching Questions Use the following to answer questions 1-10: Choose the correct answer from the list below. Not all of the answers will be used. a) annealing b) mRNA molecules c) synonyms d) linear e) amino acid f) Tm g) retroviruses h) exon i) Erwin Chargaff j) release factor k) gene expression l) Rosalyn Franklin 1 ____________ The information-carrying intermediates of translation. Ans: b Section: Introduction 2 The flow of genetic information from DNA to protein is called ____________. Ans: k Section: Introduction 3 ____________ Scientist who noted the A:T and G:C ratios in DNA are approximately 1:1. Ans: i Section: 4.1 4 The temperature at which half the DNA helical character is lost is referred to as ____________. Ans: f Section: 4.2 5 DNA renaturation after melting is called ____________. Ans: a Section: 4.2 6 DNA can exist in both circular and ____________ forms. Ans: d Section: 4.2
Chapter 4 DNA,RNA,and the Flow of Genetic Information 2 7 Organisms in which the flow of genetic information can be RNA->DNA. Ans:g Section:4.3 8 Codons that specify the same amino acids are termed Ans:c Section:4.5 9 A three-base codon defines a specific Ans:e Section:4.5 10 Stop codons are read by Ans:j Section:4.5 Fill in the Blank Questions 1 The enzyme that is capable of synthesizing DNA from an RNA template is Ans:reverse transcriptase Section:4.3 2 is the most abundant type of RNA in a cell. Ans:Ribosomal RNA Section:4.4 and Table 4.2. 3 Each amino acid residue in a protein is encoded by a set of three bases on mRNA referred to as a Ans:codon Section:4.5 4 In an amino acyl-tRNA,the amino acid is attached to the CCA sequence at the end of the tRNA. Ans:3'Section:4.4 5 mRNA higher organisms are formed by splicing together expressed regions after removal of Ans:introns Section:4.6 6 In bacterial mRNA,the initiating AUG codon is preceded several nucleotides away by a purine- rich sequence called the which base-pairs with a complimentary sequence in an rRNA. Ans:Shine-Dalgarno sequence Section:4.5 Page2
Chapter 4 DNA, RNA, and the Flow of Genetic Information Page 2 2 7 ____________ Organisms in which the flow of genetic information can be RNADNA. Ans: g Section: 4.3 8 Codons that specify the same amino acids are termed ____________. Ans: c Section: 4.5 9 A three-base codon defines a specific ____________. Ans: e Section: 4.5 10 Stop codons are read by ____________. Ans: j Section: 4.5 Fill in the Blank Questions 1 The enzyme that is capable of synthesizing DNA from an RNA template is __________________. Ans: reverse transcriptase Section: 4.3 2 __________________ is the most abundant type of RNA in a cell. Ans: Ribosomal RNA Section: 4.4 and Table 4.2. 3 Each amino acid residue in a protein is encoded by a set of three bases on mRNA referred to as a __________________. Ans: codon Section: 4.5 4 In an amino acyl-tRNA, the amino acid is attached to the CCA sequence at the _________ end of the tRNA. Ans: 3' Section: 4.4 5 mRNA higher organisms are formed by splicing together expressed regions after removal of __________________. Ans: introns Section: 4.6 6 In bacterial mRNA, the initiating AUG codon is preceded several nucleotides away by a purinerich sequence called the __________________ , which base-pairs with a complimentary sequence in an rRNA. Ans: Shine-Dalgarno sequence Section: 4.5
Chapter 4 DNA,RNA,and the Flow of Genetic Information 7 The nucleoside that is composed of a D-ribose linked to a cytosine base is called Ans:cytidine Section:4.1 8 The phenomenon that stacked bases in double-helical DNA absorbed less UV light than the unstacked bases in single-stranded DNA is referred to as Ans:hypochromism or the hypochromic effect Section:4.2 9 DNA polymerase reads the template strand in the direction. Ans:3'to 5'Section:4.3 10 In DNA and RNA synthesis,the new strand growth is always in the direction. Ans:5'to 3'Section:4.3 Multiple Choice Questions 1 The difference in RNA bases compared to DNA bases is A)RNA contains A instead of T. D)RNA contains A instead of U. B) RNA contains U instead of G. E) None of the above. C) RNA contains U instead of T. Ans:C Section:4.1 2 How does a nucleotide differ from a nucleoside? A) Nucleosides are found in DNA,whereas nucleotides are found in RNA B) Purines are only found in nucleotides. C) Nucleosides contain only deoxyribose sugars. D) A nucleotide is a nucleoside with a phosphate ester linked to the sugar E) None of the above. Ans:D Section:4.1 3 What is the nucleotide sequence on the DNA template strand that yields the CUA codon for leucine? A)AUC D) GAT B) TAG E) CUA C)CTA Ans:B Section:4.5 4 How many different sequence possibilities are there for a DNA polymer that is 10 bases long? A)262,144B)40C)4000D)1,048,576E)100,000 Ans:D Section:4.1 5 The technique(s)used by Franklin and Wilkins to deduce the structure of DNA was A)absorbance spectrophotometry. D)All of the above. B)electron microscopy. E) None of the above. C)X-ray diffraction. Ans:C Section:4.2 Page 3
Chapter 4 DNA, RNA, and the Flow of Genetic Information Page 3 3 7 The nucleoside that is composed of a D-ribose linked to a cytosine base is called __________________. Ans: cytidine Section: 4.1 8 The phenomenon that stacked bases in double-helical DNA absorbed less UV light than the unstacked bases in single-stranded DNA is referred to as _________________. Ans: hypochromism or the hypochromic effect Section: 4.2 9 DNA polymerase reads the template strand in the ______________ direction. Ans: 3' to 5' Section: 4.3 10 In DNA and RNA synthesis, the new strand growth is always in the ___________ direction. Ans: 5' to 3' Section: 4.3 Multiple Choice Questions 1 The difference in RNA bases compared to DNA bases is A) RNA contains A instead of T. D) RNA contains A instead of U. B) RNA contains U instead of G. E) None of the above. C) RNA contains U instead of T. Ans: C Section: 4.1 2 How does a nucleotide differ from a nucleoside? A) Nucleosides are found in DNA, whereas nucleotides are found in RNA. B) Purines are only found in nucleotides. C) Nucleosides contain only deoxyribose sugars. D) A nucleotide is a nucleoside with a phosphate ester linked to the sugar . E) None of the above. Ans: D Section: 4.1 3 What is the nucleotide sequence on the DNA template strand that yields the CUA codon for leucine? A) AUC D) GAT B) TAG E) CUA C) CTA Ans: B Section: 4.5 4 How many different sequence possibilities are there for a DNA polymer that is 10 bases long? A) 262,144 B) 40 C) 4000 D) 1,048,576 E) 100,000 Ans: D Section: 4.1 5 The technique(s) used by Franklin and Wilkins to deduce the structure of DNA was A) absorbance spectrophotometry. D) All of the above. B) electron microscopy. E) None of the above. C) X-ray diffraction. Ans: C Section: 4.2
Chapter 4 DNA,RNA,and the Flow of Genetic Information 4 6 The feature(s)of DNA deduced by Watson and Crick included A)two antiparallel polynucleotide chains coiled in a helix around a common axis. B) the pyrimidine and purine bases lie on the inside of the helix. c) the bases are nearly perpendicular to the axis. D) All of the above. E)None of the above Ans:D Section:4.2 7 The chemical forces that contribute to the stability of the DNA due to the base stacking present in the DNA helix are A) hydrogen bonds. D) b and c B) van der Waals. E) None of the above. C)disulfide bonds. Ans:B Section:4.2 8 What is the approximate error rate in DNA replication? A)1×10-8B)1×10-6C)1×10-lsD)1×10-10E)None of the above. Ans:A Section:4.3 9 What are the common promoter regions found in bacterial genes? A)a Pribnow box about-10 and a-35 region B)a TATA box about-25 and a CAAT box about-75 C)a Pribnow box about-10 and a TATA box about-25 D)a TATA box about-25 and a-35 region E)None of the above. Ans:A Section:4.4 10 Which of the following is correct concerning the adaptor molecule tRNA? A) tRNA contains an anticodon sequence that serves as the template recognition site. B)The amino acid is attached to the 5'end of tRNA. C) tRNA contains a poly A tail at the 3'end. D) tRNA is the smallest RNA in the cell. E) tRNA serves as the gene in some viruses. Ans:D Section:4.4 11 Features of the genetic code include A)a codon is defined by three bases. D a and c. B)the code overlaps. E) a and b. C)the code is degenerate. Ans:D Section:4.5 12 The first amino acid in bacterial proteins is A)Met.B)fGly.C)fMet.D)Gly.E)None of the above Ans:C Section:4.5 13 In which codon position(s)do most synonyms differ? A)first position D) a and c B) second position E) None of the above C)third position Ans:C Section:4.5 Page4
Chapter 4 DNA, RNA, and the Flow of Genetic Information Page 4 4 6 The feature(s) of DNA deduced by Watson and Crick included A) two antiparallel polynucleotide chains coiled in a helix around a common axis. B) the pyrimidine and purine bases lie on the inside of the helix. C) the bases are nearly perpendicular to the axis. D) All of the above. E) None of the above. Ans: D Section: 4.2 7 The chemical forces that contribute to the stability of the DNA due to the base stacking present in the DNA helix are A) hydrogen bonds. D) b and c. B) van der Waals. E) None of the above. C) disulfide bonds. Ans: B Section: 4.2 8 What is the approximate error rate in DNA replication? A) 1 10 8 B) 1 10 6 C) 1 10 15 D) 1 10 10 E) None of the above. Ans: A Section: 4.3 9 What are the common promoter regions found in bacterial genes? A) a Pribnow box about –10 and a –35 region B) a TATA box about –25 and a CAAT box about –75 C) a Pribnow box about –10 and a TATA box about –25 D) a TATA box about –25 and a –35 region E) None of the above. Ans: A Section: 4.4 10 Which of the following is correct concerning the adaptor molecule tRNA? A) tRNA contains an anticodon sequence that serves as the template recognition site. B) The amino acid is attached to the 5' end of tRNA. C) tRNA contains a poly A tail at the 3' end. D) tRNA is the smallest RNA in the cell. E) tRNA serves as the gene in some viruses. Ans: D Section: 4.4 11 Features of the genetic code include A) a codon is defined by three bases. D) a and c. B) the code overlaps. E) a and b. C) the code is degenerate. Ans: D Section: 4.5 12 The first amino acid in bacterial proteins is A) Met. B) fGly. C) fMet. D) Gly. E) None of the above. Ans: C Section: 4.5 13 In which codon position(s) do most synonyms differ? A) first position D) a and c B) second position E) None of the above C) third position Ans: C Section: 4.5
Chapter 4 DNA,RNA,and the Flow of Genetic Information 5 14 The sites for intron splicing consensus sequences are often A) AC----------AAAA D) All of the above. B) GU- --AG. E) None of the above. c) AU-. ----GC. Ans:B Section:4.6 15 Ribosomes are composed of A)DNA.B)rRNA.C)protein.D)All of the above.E)b and c. Ans:D Section:4.4 Short-Answer Questions 1 Draw two nucleotides in DNA showing the linkage between the sugars linked. Ans: Base Base CH The 3'oxygen of one nucleotide is linked to a phosphorous atom,which is linked to the oxygen on the 5'carbon on the next sugar.Two extra oxygens should be attached to the phosphorus atom,and the phosphate should be shown ionized at neutral pH.There should be no oxygen at the 2'position of the sugar. Section:4.1 and Figure 4.22 2 What advantage do phosphodiesters have compared to other esters? Ans:The negative charge serves to repel nucleophilic species such as OH.Thus the phophodiester linkage is more stable because it is more resistant to hydrolytic cleavage. Section:4.1.1 3 Describe the DNA helix proposed by Watson and Crick. Ans:The DNA model proposed by Watson and Crick contains two DNA polymer strands coiled around a common axis.The strands are orientated in opposite directions from 5'to 3'(antiparallel),and the two strands are twisted in a right-handed coil.The sugar- phosphate backbone is located on the outside.The base pairs are stacked in the center of the helix and are stabilized by specific hydrogen bonds between AT and GC base pairs. The base pairs lie perpendicular to the axis,and there are 10 base pairs per turn with a helical repeat of 34 angstroms. Section:4.1 Page 5
Chapter 4 DNA, RNA, and the Flow of Genetic Information Page 5 5 14 The sites for intron splicing consensus sequences are often A) AC-------------------AAAA. D) All of the above. B) GU-------------------AG. E) None of the above. C) AU-------------------GC. Ans: B Section: 4.6 15 Ribosomes are composed of A) DNA. B) rRNA. C) protein. D) All of the above. E) b and c. Ans: D Section: 4.4 Short-Answer Questions 1 Draw two nucleotides in DNA showing the linkage between the sugars linked. Ans: O O H CH2 O P O O O H CH2 O P O O O Base Base O The 3' oxygen of one nucleotide is linked to a phosphorous atom, which is linked to the oxygen on the 5' carbon on the next sugar. Two extra oxygens should be attached to the phosphorus atom, and the phosphate should be shown ionized at neutral pH. There should be no oxygen at the 2' position of the sugar. Section: 4.1 and Figure 4.22 2 What advantage do phosphodiesters have compared to other esters? Ans: The negative charge serves to repel nucleophilic species such as OH-. Thus the phophodiester linkage is more stable because it is more resistant to hydrolytic cleavage. Section: 4.1.1 3 Describe the DNA helix proposed by Watson and Crick. Ans: The DNA model proposed by Watson and Crick contains two DNA polymer strands coiled around a common axis. The strands are orientated in opposite directions from 5' to 3' (antiparallel), and the two strands are twisted in a right-handed coil. The sugar- phosphate backbone is located on the outside. The base pairs are stacked in the center of the helix and are stabilized by specific hydrogen bonds between AT and GC base pairs. The base pairs lie perpendicular to the axis, and there are 10 base pairs per turn with a helical repeat of 34 angstroms. Section: 4.1
Chapter 4 DNA,RNA,and the Flow of Genetic Information 6 4 Draw the Hydrogen bonded base pairs of A to T and show why A does not hydrogen bond to C. Ans: H H H H-N d-Rib d-Rib d-Rib d-Rib No H-bonds can form between the function: groups in A and C. Section:4.1 5 Briefly describe the Meselson and Stahl experiment that indicated that DNA replication is semiconservative Ans:Meselson and Stahl grew bacteria in the presence of I5N,or"heavy"nitrogen.They rapidly replaced the I5N media with 4N,or light nitrogen.DNA was extracted at various time intervals during the growth of the bacteria,representing different stages of replication(generations).They examined the DNA using density-gradient equilibrium sedimentation and observed that no"heavy"DNA was present in the first generation,but that the DNA was intermediate between light and heavy.After the second generation, there were equal amounts of intermediate and light.This confirmed that one strand of the parent DNA is present in each daughter strand of replicated DNA. Section:4.2 6 What is DNA hybridization? Ans:DNA hybridization is the process whereby strands of nearly complimentary DNA from different organisms or one strand of DNA and one strand of RNA base pair to form a helix. Section:4.2 7 What are the minimal requirements for DNA replication? Ans:DNA replication requires DNA template;all four deoxynucleoside triphosphates dATP, dTTP,dGTP,dCTP(dNTPs);a primer polynucleotide with a free 3'OH;magnesium ion; and DNA polymerase. Section:4.3 8 How is the dNTP added to a DNA strand at the 3'end? Ans:The drawing should indicate clearly how the 3'OH oxygen attacks the a phosphate on the incoming dNTP with the displacement of pyrophosphate. Section:4.3 and Figure 4.22 9 How does RNA polymerase differ from DNA polymerase? Ans:Although similar in many respects to DNA polymerase,RNA polymerase does not require a primer,nor does it have the nuclease"proofreading"capacity. Section:4.4 Page 6
Chapter 4 DNA, RNA, and the Flow of Genetic Information Page 6 6 4 Draw the Hydrogen bonded base pairs of A to T and show why A does not hydrogen bond to C. Ans: N N O O CH3 H N N N N N H H d-Rib d-Rib d-Rib d-Rib N N O N H H N N N N N H H No H-bonds can form between the functional groups in A and C. Section: 4.1 5 Briefly describe the Meselson and Stahl experiment that indicated that DNA replication is semiconservative Ans: Meselson and Stahl grew bacteria in the presence of 15N, or “heavy” nitrogen. They rapidly replaced the 15N media with 14N, or light nitrogen. DNA was extracted at various time intervals during the growth of the bacteria, representing different stages of replication (generations). They examined the DNA using density-gradient equilibrium sedimentation and observed that no “heavy” DNA was present in the first generation, but that the DNA was intermediate between light and heavy. After the second generation, there were equal amounts of intermediate and light. This confirmed that one strand of the parent DNA is present in each daughter strand of replicated DNA. Section: 4.2 6 What is DNA hybridization? Ans: DNA hybridization is the process whereby strands of nearly complimentary DNA from different organisms or one strand of DNA and one strand of RNA base pair to form a helix. Section: 4.2 7 What are the minimal requirements for DNA replication? Ans: DNA replication requires DNA template; all four deoxynucleoside triphosphates dATP, dTTP, dGTP, dCTP (dNTPs); a primer polynucleotide with a free 3' OH; magnesium ion; and DNA polymerase. Section: 4.3 8 How is the dNTP added to a DNA strand at the 3' end? Ans: The drawing should indicate clearly how the 3'OH oxygen attacks the α phosphate on the incoming dNTP with the displacement of pyrophosphate. Section: 4.3 and Figure 4.22 9 How does RNA polymerase differ from DNA polymerase? Ans: Although similar in many respects to DNA polymerase, RNA polymerase does not require a primer, nor does it have the nuclease “proofreading” capacity. Section: 4.4
Chapter 4 DNA,RNA,and the Flow of Genetic Information 7 10 What is a consensus sequence? Ans:A consensus sequence is a common sequence motif found in a number of genes or DNA regions.While all the sequences may not be exactly alike,and may differ in one or several bases,the sequences have a very similar structure,and implied common function. Section:4.4 11 What are the two primary components of a gene? Ans:Most genes are preceded by a promoter and contain distinct start and stop sites for RNA transcription.Thus,the promoter region and a transcribed region are the two major defined portions. Section:4.4 12 What are two features of eukaryotic mRNA that are unique as compared to prokaryotic mRNA. Ans:Eukaryotic mRNA has a special nucleotide"cap"at the 5'end and a poly A tail at the 3' end. Section:4.4 and Figure 4.29 13 Why are deletion and insertion mutations usually lethal? Ans:The genetic code has no punctuation.The sequence of bases is read sequentially from a fixed starting point codon,AUG.After the reading begins,every set of three bases codes for one amino acid in the protein sequence.If an insertion or a deletion occurs,there will be a completely different set of codes after the mutation which results in a garbage sequence and a nonfunctional protein. Section:4.5 14 What is an advantage of codon degeneracy? Ans:Changes in the third position often have no effect on the final amino acid used in translation.Thus,degeneracy minimizes the deleterious effect of DNA mutations. Section:4.5 15 The genetic code is not universal.Where are exceptions found? Ans:Exceptions are found in several places.The most notable are those in mitochondria. Ciliated protozoans also have some unique codons. Section:4.5 Page 7
Chapter 4 DNA, RNA, and the Flow of Genetic Information Page 7 7 10 What is a consensus sequence? Ans: A consensus sequence is a common sequence motif found in a number of genes or DNA regions. While all the sequences may not be exactly alike, and may differ in one or several bases, the sequences have a very similar structure, and implied common function. Section: 4.4 11 What are the two primary components of a gene? Ans: Most genes are preceded by a promoter and contain distinct start and stop sites for RNA transcription. Thus, the promoter region and a transcribed region are the two major defined portions. Section: 4.4 12 What are two features of eukaryotic mRNA that are unique as compared to prokaryotic mRNA. Ans: Eukaryotic mRNA has a special nucleotide “cap” at the 5' end and a poly A tail at the 3' end. Section: 4.4 and Figure 4.29 13 Why are deletion and insertion mutations usually lethal? Ans: The genetic code has no punctuation. The sequence of bases is read sequentially from a fixed starting point codon, AUG. After the reading begins, every set of three bases codes for one amino acid in the protein sequence. If an insertion or a deletion occurs, there will be a completely different set of codes after the mutation which results in a garbage sequence and a nonfunctional protein. Section: 4.5 14 What is an advantage of codon degeneracy? Ans: Changes in the third position often have no effect on the final amino acid used in translation. Thus, degeneracy minimizes the deleterious effect of DNA mutations. Section: 4.5 15 The genetic code is not universal. Where are exceptions found? Ans: Exceptions are found in several places. The most notable are those in mitochondria. Ciliated protozoans also have some unique codons. Section: 4.5
