Question 1

What is the function of the enzyme topoisomerase in DNA replication?

Accepted Answer

A)  Relieving strain in the DNA ahead of the replication fork caused by the untwisting of the double helix. 
B)  Elongating new DNA at a replication fork by adding nucleotides to the existing chain. 
C)  Reattaching the hydrogen bonds between the base pairs in the double helix. 
D)  Building RNA primers using the parental DNA strand as a template. 
A)  Relieving strain in the DNA ahead of the replication fork caused by the untwisting of the double helix. 
B)  Elongating new DNA at a replication fork by adding nucleotides to the existing chain. 
C)  Reattaching the hydrogen bonds between the base pairs in the double helix. 
D)  Building RNA primers using the parental DNA strand as a template.

Question 2

Within a double-stranded DNA molecule, adenine forms hydrogen bonds with thymine, and cytosine forms hydrogen bonds with guanine. What is the significance of the structural arrangement?

Accepted Answer

A)  It allows variable width of the double helix. 
B)  It permits complementary base pairing. 
C)  It determines the tertiary structure of a DNA molecule. 
D)  It determines the type of protein produced. 
A)  It allows variable width of the double helix. 
B)  It permits complementary base pairing. 
C)  It determines the tertiary structure of a DNA molecule. 
D)  It determines the type of protein produced.

Question 3

Which of the following statements correctly describes the difference between the leading strand and the lagging strand in DNA replication?

Accepted Answer

A)  The leading strand is synthesised in the 3' → 5' direction in a discontinuous fashion, while the lagging strand is synthesised in the 5' → 3' direction in a continuous fashion. 
B)  The leading strand is synthesised continuously in the 5' → 3' direction, while the lagging strand is synthesised discontinuously in the 5' → 3' direction. 
C)  The leading strand requires an RNA primer, whereas the lagging strand does not. 
D)  There are different DNA polymerases involved in elongation of the leading strand and the lagging strand. 
A)  The leading strand is synthesised in the 3' → 5' direction in a discontinuous fashion, while the lagging strand is synthesised in the 5' → 3' direction in a continuous fashion. 
B)  The leading strand is synthesised continuously in the 5' → 3' direction, while the lagging strand is synthesised discontinuously in the 5' → 3' direction. 
C)  The leading strand requires an RNA primer, whereas the lagging strand does not. 
D)  There are different DNA polymerases involved in elongation of the leading strand and the lagging strand.

Question 4

It became apparent to Watson and Crick (1953) after completion of their model that the DNA molecule could carry a vast amount of hereditary information. Which of the following characteristics of DNA is responsible for this?

Accepted Answer

A)  sequence of bases 
B)  phosphate-sugar backbones 
C)  complementary pairing of bases 
D)  side groups of nitrogenous bases 
A)  sequence of bases 
B)  phosphate-sugar backbones 
C)  complementary pairing of bases 
D)  side groups of nitrogenous bases

Question 5

Individuals with the disorder xeroderma pigmentosum are hypersensitive to sunlight, and mutations to the DNA in their skin cells are left uncorrected. Why are the mutations not corrected in individuals with this disorder?

Accepted Answer

A)  The disorder makes cells unable to replicate DNA. 
B)  The disorder causes mitosis to stop during metaphase. 
C)  The disorder makes cells unable to form chromosomes. 
D)  The disorder causes cells to be unable to repair thymine dimers. 
A)  The disorder makes cells unable to replicate DNA. 
B)  The disorder causes mitosis to stop during metaphase. 
C)  The disorder makes cells unable to form chromosomes. 
D)  The disorder causes cells to be unable to repair thymine dimers.

Question 6

In his work with pneumonia-causing bacteria and mice, Griffith found that

Accepted Answer

A)  the protein coat from pathogenic cells was able to transform nonpathogenic cells. 
B)  heat-killed pathogenic cells caused pneumonia. 
C)  some substance from pathogenic cells was transferred to nonpathogenic cells, making them pathogenic. 
D)  the polysaccharide coat of bacteria caused pneumonia. 
A)  the protein coat from pathogenic cells was able to transform nonpathogenic cells. 
B)  heat-killed pathogenic cells caused pneumonia. 
C)  some substance from pathogenic cells was transferred to nonpathogenic cells, making them pathogenic. 
D)  the polysaccharide coat of bacteria caused pneumonia.

Question 7

In E. coli, there is a mutation in a gene called dnaB that alters the helicase that normally acts at the origin of replication. Which of the following events would you expect to occur as a result of this mutation?

Accepted Answer

A)  Additional proofreading will occur. 
B)  No replication fork will be formed. 
C)  Replication will occur via RNA polymerase alone. 
D)  Replication will require a DNA template from another source. 
A)  Additional proofreading will occur. 
B)  No replication fork will be formed. 
C)  Replication will occur via RNA polymerase alone. 
D)  Replication will require a DNA template from another source.

Question 8

What is meant by the description "antiparallel" regarding the two strands that make up the DNA double helix?

Accepted Answer

A)  The double helix structure of DNA creates nonparallel strands. 
B)  The 5' to 3' direction of one strand runs counter to the 5' to 3' direction of the other strand. 
C)  Base pairings create unequal spacing between the two DNA strands. 
D)  One strand contains only purines and the other contains only pyrimidines. 
A)  The double helix structure of DNA creates nonparallel strands. 
B)  The 5' to 3' direction of one strand runs counter to the 5' to 3' direction of the other strand. 
C)  Base pairings create unequal spacing between the two DNA strands. 
D)  One strand contains only purines and the other contains only pyrimidines.

Question 9

In E. coli, which enzyme catalyses the elongation of a new DNA strand in the 5' → 3' direction?

Accepted Answer

A)  primase 
B)  DNA ligase 
C)  DNA polymerase III 
D)  helicase 
A)  primase 
B)  DNA ligase 
C)  DNA polymerase III 
D)  helicase

Question 10

In DNA replication in E. coli, the enzyme primase is used to attach a 5 to 10 base ribonucleotide strand complementary to the parental DNA strand. The RNA strand serves as a starting point for the DNA polymerase that replicates the DNA. If a mutation occurred in the primase gene, which of the following results would you expect?

Accepted Answer

A)  Replication would only occur on the leading strand. 
B)  Replication would only occur on the lagging strand. 
C)  Replication would not occur on either the leading or lagging strand. 
D)  Replication would not be affected as the enzyme primase in involved with RNA synthesis. 
A)  Replication would only occur on the leading strand. 
B)  Replication would only occur on the lagging strand. 
C)  Replication would not occur on either the leading or lagging strand. 
D)  Replication would not be affected as the enzyme primase in involved with RNA synthesis.

Question 11

In E. coli, what is the function of DNA polymerase III?

Accepted Answer

A)  to unwind the DNA helix during replication 
B)  to seal together the broken ends of DNA strands 
C)  to add nucleotides to the 3' end of a growing DNA strand 
D)  to degrade damaged DNA molecules 
A)  to unwind the DNA helix during replication 
B)  to seal together the broken ends of DNA strands 
C)  to add nucleotides to the 3' end of a growing DNA strand 
D)  to degrade damaged DNA molecules

Question 12

Use the figure to answer the following question.   In the late 1950s, Meselson and Stahl grew bacteria in a medium containing "heavy" (radioactive) nitrogen (13N) and then transferred them to a medium containing 14N (non-radioactive). Which of the results in the figure would be expected after one round of DNA replication in the presence of 14N?

Accepted Answer

A)  A 
B)  B 
C)  C 
D)  D 
A)  A 
B)  B 
C)  C 
D)  D

Question 13

Which of the following effects might be caused by reduced or very little active telomerase activity?

Accepted Answer

A)  Cells may become cancerous. 
B)  Telomere lengthens in germ cells. 
C)  Cells age and begin to lose function. 
D)  Cells maintain normal functioning. 
A)  Cells may become cancerous. 
B)  Telomere lengthens in germ cells. 
C)  Cells age and begin to lose function. 
D)  Cells maintain normal functioning.

Question 14

You briefly expose bacteria undergoing DNA replication to radioactively labelled nucleotides. When you centrifuge the DNA isolated from the bacteria, the DNA separates into two classes. One class of labelled DNA includes very large molecules (thousands or even millions of nucleotides long), and the other includes short stretches of DNA (several hundred to a few thousand nucleotides in length). Which two classes of DNA do these different samples represent?

Accepted Answer

A)  leading strands and Okazaki fragments 
B)  lagging strands and Okazaki fragments 
C)  Okazaki fragments and RNA primers 
D)  leading strands and RNA primers 
A)  leading strands and Okazaki fragments 
B)  lagging strands and Okazaki fragments 
C)  Okazaki fragments and RNA primers 
D)  leading strands and RNA primers

Question 15

The lagging strand is characterised by a series of short segments of DNA (Okazaki fragments) that will be joined together to form a finished lagging strand. The experiments that led to the discovery of Okazaki fragments gave evidence for which of the following ideas?

Accepted Answer

A)  DNA polymerase is an enzyme that synthesises leading and lagging strands during replication only in one direction. 
B)  DNA is a polymer consisting of four monomers: adenine, thymine, guanine and cytosine. 
C)  DNA is the genetic material. 
D)  Bacterial replication is fundamentally different from eukaryotic replication. The key should not be way longer than the distractors. 
A)  DNA polymerase is an enzyme that synthesises leading and lagging strands during replication only in one direction. 
B)  DNA is a polymer consisting of four monomers: adenine, thymine, guanine and cytosine. 
C)  DNA is the genetic material. 
D)  Bacterial replication is fundamentally different from eukaryotic replication. The key should not be way longer than the distractors.

Question 16

The spontaneous loss of amino groups from adenine in DNA results in hypoxanthine, an uncommon base, opposite thymine. What combination of proteins could repair such damage?

Accepted Answer

A)  nuclease, DNA polymerase, DNA ligase 
B)  telomerase, primase, DNA polymerase 
C)  telomerase, helicase, single-strand binding protein 
D)  DNA ligase, replication fork proteins, adenylyl cyclase 
A)  nuclease, DNA polymerase, DNA ligase 
B)  telomerase, primase, DNA polymerase 
C)  telomerase, helicase, single-strand binding protein 
D)  DNA ligase, replication fork proteins, adenylyl cyclase

Question 17

Which of the following molecular characteristics cause histones to bind tightly to DNA?

Accepted Answer

A)  Histones are positively charged, and DNA is negatively charged. 
B)  Histones are negatively charged, and DNA is positively charged. 
C)  Both histones and DNA are strongly hydrophobic. 
D)  Histones are covalently linked to the DNA. 
A)  Histones are positively charged, and DNA is negatively charged. 
B)  Histones are negatively charged, and DNA is positively charged. 
C)  Both histones and DNA are strongly hydrophobic. 
D)  Histones are covalently linked to the DNA.

Question 18

Hershey and Chase (1952) set out to determine what molecule served as the unit of inheritance. They completed a series of experiments in which E. coli was infected by a T2 virus. Which molecular component of the T2 virus actually ended up inside the cell?

Accepted Answer

A)  protein 
B)  RNA 
C)  ribosome 
D)  DNA 
A)  protein 
B)  RNA 
C)  ribosome 
D)  DNA

Question 19

Hershey and Chase (1952) used a DNA-based virus for their work. How might the results have been different if they had used an RNA virus?

Accepted Answer

A)  With an RNA virus, radioactive protein would have been in the final pellet. 
B)  With an RNA virus, radioactive RNA would have been in the final pellet. 
C)  With an RNA virus, neither sample would have had a radioactive pellet. 
D)  With an RNA virus, the protein shell would have been radioactive in both samples. 
A)  With an RNA virus, radioactive protein would have been in the final pellet. 
B)  With an RNA virus, radioactive RNA would have been in the final pellet. 
C)  With an RNA virus, neither sample would have had a radioactive pellet. 
D)  With an RNA virus, the protein shell would have been radioactive in both samples.

Question 20

If a cell were unable to produce histone proteins, which of the following results would be a likely effect on the cell?

Accepted Answer

A)  There would be an increase in the amount of DNA produced during replication. 
B)  The cell's DNA could not be packed into its nucleus. 
C)  Spindle fibres would not form during prophase. 
D)  Amplification of other genes would compensate for the lack of histones. 
A)  There would be an increase in the amount of DNA produced during replication. 
B)  The cell's DNA could not be packed into its nucleus. 
C)  Spindle fibres would not form during prophase. 
D)  Amplification of other genes would compensate for the lack of histones.

Exam 16: The Molecular Basis of Inheritance

What is the function of the enzyme topoisomerase in DNA replication?

Within a double-stranded DNA molecule, adenine forms hydrogen bonds with thymine, and cytosine forms hydrogen bonds with guanine. What is the significance of the structural arrangement?

Which of the following statements correctly describes the difference between the leading strand and the lagging strand in DNA replication?

It became apparent to Watson and Crick (1953) after completion of their model that the DNA molecule could carry a vast amount of hereditary information. Which of the following characteristics of DNA is responsible for this?

Individuals with the disorder xeroderma pigmentosum are hypersensitive to sunlight, and mutations to the DNA in their skin cells are left uncorrected. Why are the mutations not corrected in individuals with this disorder?

In his work with pneumonia-causing bacteria and mice, Griffith found that

In E. coli, there is a mutation in a gene called dnaB that alters the helicase that normally acts at the origin of replication. Which of the following events would you expect to occur as a result of this mutation?

What is meant by the description "antiparallel" regarding the two strands that make up the DNA double helix?

In E. coli, which enzyme catalyses the elongation of a new DNA strand in the 5' → 3' direction?

In E. coli, what is the function of DNA polymerase III?

Which of the following effects might be caused by reduced or very little active telomerase activity?

The lagging strand is characterised by a series of short segments of DNA (Okazaki fragments) that will be joined together to form a finished lagging strand. The experiments that led to the discovery of Okazaki fragments gave evidence for which of the following ideas?

The spontaneous loss of amino groups from adenine in DNA results in hypoxanthine, an uncommon base, opposite thymine. What combination of proteins could repair such damage?

Which of the following molecular characteristics cause histones to bind tightly to DNA?

Hershey and Chase (1952) set out to determine what molecule served as the unit of inheritance. They completed a series of experiments in which E. coli was infected by a T2 virus. Which molecular component of the T2 virus actually ended up inside the cell?

Hershey and Chase (1952) used a DNA-based virus for their work. How might the results have been different if they had used an RNA virus?

If a cell were unable to produce histone proteins, which of the following results would be a likely effect on the cell?

Evolution, the Themes of Biology, and Scientific Inquiry

The Chemical Context of Life

Water and Life

Carbon and the Molecular Diversity of Life

The Structure and Function of Large Biological Molecules

A Tour of the Cell

Membrane Structure and Function

An Introduction to Metabolism

Cellular Respiration and Fermentation

Photosynthesis

Cell Communication

The Cell Cycle

Meiosis and Sexual Life Cycles

Mendel and the Gene Idea

The Chromosomal Basis of Inheritance

Gene Expression: From Gene to Protein

Regulation of Gene Expression

Viruses

Dna Tools and Biotechnology

Genomes and Their Evolution

Descent With Modification: a Darwinian View of Life

The Evolution of Populations

The Origin of Species

The History of Life on Earth

Phylogeny and the Tree of Life

Bacteria and Archaea

Protists

Plant Diversity I: How Plants Colonised Land

Plant Diversity Ii: the Evolution of Seed Plants

Fungi

An Overview of Animal Diversity

An Introduction to Invertebrates

The Origin and Evolution of Vertebrates

Vascular Plant Structure, Growth, and Development

Resource Acquisition and Transport in Vascular Plants

Soil and Plant Nutrition

Angiosperm Reproduction and Biotechnology

Plant Responses to Internal and External Signals

Basic Principles of Animal Form and Function

Animal Nutrition

Circulation and Gas Exchange

The Immune System

Osmoregulation and Excretion

Hormones and the Endocrine System

Animal Reproduction

Animal Development

Neurons, Synapses, and Signalling

Nervous Systems

Sensory and Motor Mechanisms

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