Question 1

Which of the following molecule(s)help(s)to hold the DNA strands apart while they are being replicated?

Accepted Answer

A) primase 
B) ligase 
C) DNA polymerase 
D) single-strand binding proteins 
A) primase 
B) ligase 
C) DNA polymerase 
D) single-strand binding proteins

Question 2

The segment of DNA shown in the figure above has restriction sites I and II,which create restriction fragments A,B,and C.Which of the gels produced by electrophoresis shown below best represents the separation and identity of these fragments?

Accepted Answer

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

Question 3

In the late 1950s,Meselson and Stahl grew bacteria in a medium containing "heavy" (radioactive)nitrogen (15N)and then transferred them to a medium containing 14N,which is a less radioactive form of nitrogen.They then extracted DNA from the bacteria and centrifuged it to separate the DNA of different densities.Once the pattern found after one round of replication was observed,Meselson and Stahl could be confident of which of the following conclusions?

Accepted Answer

A) Replication is semiconservative. 
B) Replication is not dispersive. 
C) Replication is not semiconservative. 
D) Replication is not conservative. 
A) Replication is semiconservative. 
B) Replication is not dispersive. 
C) Replication is not semiconservative. 
D) Replication is not conservative.

Question 4

In a linear eukaryotic chromatin sample,which of the following strands is looped into nucleosomes?

Accepted Answer

A) DNA without attached histones 
B) RNA primers 
C) the 10-nm chromatin fiber 
D) the 30-nm chromatin fiber 
A) DNA without attached histones 
B) RNA primers 
C) the 10-nm chromatin fiber 
D) the 30-nm chromatin fiber

Question 5

Which of the following statements describes one difference between DNA replication in prokaryotes and DNA replication in eukaryotes?

Accepted Answer

A) Prokaryotic chromosomes have histones,whereas eukaryotic chromosomes do not. 
B) Prokaryotic chromosomes have a single origin of replication,whereas eukaryotic chromosomes have many. 
C) The rate of elongation during DNA replication is slower in prokaryotes than in eukaryotes. 
D) Prokaryotes produce Okazaki fragments during DNA replication,but eukaryotes do not. 
A) Prokaryotic chromosomes have histones,whereas eukaryotic chromosomes do not. 
B) Prokaryotic chromosomes have a single origin of replication,whereas eukaryotic chromosomes have many. 
C) The rate of elongation during DNA replication is slower in prokaryotes than in eukaryotes. 
D) Prokaryotes produce Okazaki fragments during DNA replication,but eukaryotes do not.

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

Which of the following statements correctly describes how the leading and the lagging strands of DNA formed during DNA replication differ?

Accepted Answer

A) The leading strand is synthesized in the same direction as the movement of the replication fork,and the lagging strand is synthesized in the opposite direction. 
B) The leading strand is synthesized by adding nucleotides to the 3' end of the growing strand,and the lagging strand is synthesized by adding nucleotides to the 5' end. 
C) The lagging strand is synthesized continuously,whereas the leading strand is synthesized in short fragments that are ultimately stitched together. 
D) The leading strand is synthesized at twice the rate of the lagging strand. 
A) The leading strand is synthesized in the same direction as the movement of the replication fork,and the lagging strand is synthesized in the opposite direction. 
B) The leading strand is synthesized by adding nucleotides to the 3' end of the growing strand,and the lagging strand is synthesized by adding nucleotides to the 5' end. 
C) The lagging strand is synthesized continuously,whereas the leading strand is synthesized in short fragments that are ultimately stitched together. 
D) The leading strand is synthesized at twice the rate of the lagging strand.

Question 8

In E.coli,which of the following enzymes removes the RNA primer from the 5' end of the DNA fragment?

Accepted Answer

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

Question 9

Which of the following statements accurately describes why Taq polymerase is used in PCR?

Accepted Answer

A) It is heat stable and can withstand the heating step of PCR. 
B) Only minute amounts are needed for each cycle of PCR. 
C) It binds more readily than other polymerases to the primers. 
D) It has regions that are complementary to the primers. 
A) It is heat stable and can withstand the heating step of PCR. 
B) Only minute amounts are needed for each cycle of PCR. 
C) It binds more readily than other polymerases to the primers. 
D) It has regions that are complementary to the primers.

Question 10

You briefly expose bacteria undergoing DNA replication to radioactively labeled nucleotides.When you centrifuge the DNA isolated from the bacteria,the DNA separates into two classes.One class of labeled 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).These two classes of DNA probably 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 11

In his transformation experiments,which of the following results did Griffith observe?

Accepted Answer

A) Mutant mice were resistant to bacterial infections. 
B) Mixing a heat-killed pathogenic strain of bacteria with a living nonpathogenic strain can convert some of the living cells into the pathogenic form. 
C) Mixing a heat-killed nonpathogenic strain of bacteria with a living pathogenic strain makes the pathogenic strain nonpathogenic. 
D) Infecting mice with nonpathogenic strains of bacteria makes them resistant to pathogenic strains. 
A) Mutant mice were resistant to bacterial infections. 
B) Mixing a heat-killed pathogenic strain of bacteria with a living nonpathogenic strain can convert some of the living cells into the pathogenic form. 
C) Mixing a heat-killed nonpathogenic strain of bacteria with a living pathogenic strain makes the pathogenic strain nonpathogenic. 
D) Infecting mice with nonpathogenic strains of bacteria makes them resistant to pathogenic strains.

Question 12

Why does a new DNA strand elongate only in the 5' to 3' direction in replication?

Accepted Answer

A) DNA polymerase begins adding nucleotides at the 5' end of the template. 
B) Okazaki fragments prevent elongation in the 3' to 5' direction. 
C) Replication must progress toward the replication fork. 
D) DNA polymerase can only add nucleotides to the free 3' end. 
A) DNA polymerase begins adding nucleotides at the 5' end of the template. 
B) Okazaki fragments prevent elongation in the 3' to 5' direction. 
C) Replication must progress toward the replication fork. 
D) DNA polymerase can only add nucleotides to the free 3' end.

Question 13

Why is it so important to be able to amplify DNA fragments when studying genes?

Accepted Answer

A) DNA fragments are too small to use individually. 
B) A gene may represent only a very small portion of the cell's DNA. 
C) Restriction enzymes cut DNA into fragments that are too small. 
D) A clone requires multiple copies of each gene per clone. 
A) DNA fragments are too small to use individually. 
B) A gene may represent only a very small portion of the cell's DNA. 
C) Restriction enzymes cut DNA into fragments that are too small. 
D) A clone requires multiple copies of each gene per clone.

Question 14

Which of the following sets of materials is required by both eukaryotes and prokaryotes for DNA replication?

Accepted Answer

A) double-stranded DNA,four kinds of DNA nucleotides,primers,origins of replication 
B) topoisomerases,telomerases,polymerases 
C) G-C rich regions,polymerases,telomerases 
D) nucleosomes,four kinds of DNA nucleotides,four kinds of RNA nucleotides 
A) double-stranded DNA,four kinds of DNA nucleotides,primers,origins of replication 
B) topoisomerases,telomerases,polymerases 
C) G-C rich regions,polymerases,telomerases 
D) nucleosomes,four kinds of DNA nucleotides,four kinds of RNA nucleotides

Question 15

E.coli cells grown on 15N medium are transferred to 14N medium and allowed to grow for two more generations (two rounds of DNA replication).DNA extracted from these cells is centrifuged.What density distribution of DNA would you expect in this experiment?

Accepted Answer

A) one high-density and one low-density band 
B) one intermediate-density band 
C) one high-density and one intermediate-density band 
D) one low-density and one intermediate-density band 
A) one high-density and one low-density band 
B) one intermediate-density band 
C) one high-density and one intermediate-density band 
D) one low-density and one intermediate-density band

Question 16

In which order do the necessary enzymes act to repair a thymine dimer by nucleotide excision repair?

Accepted Answer

A) nuclease,DNA polymerase,RNA primase 
B) helicase,DNA polymerase,DNA ligase 
C) DNA ligase,nuclease,helicase 
D) nuclease,DNA polymerase,DNA ligase 
A) nuclease,DNA polymerase,RNA primase 
B) helicase,DNA polymerase,DNA ligase 
C) DNA ligase,nuclease,helicase 
D) nuclease,DNA polymerase,DNA ligase

Question 17

What is the function of DNA polymerase III in replication in E.coli?

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 18

Which of the following statements best describes the eukaryotic chromosome?

Accepted Answer

A) It is composed of DNA alone. 
B) The nucleosome is its most basic functional subunit. 
C) The number of genes on each chromosome is different in different cell types of an organism. 
D) It consists of a single linear molecule of double-stranded DNA plus proteins. 
A) It is composed of DNA alone. 
B) The nucleosome is its most basic functional subunit. 
C) The number of genes on each chromosome is different in different cell types of an organism. 
D) It consists of a single linear molecule of double-stranded DNA plus proteins.

Question 19

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) No proofreading will occur. 
B) The DNA strands at the origin of replication will separate,but replication will not progress. 
C) The DNA will supercoil. 
D) DNA polymerase I will not function correctly. 
A) No proofreading will occur. 
B) The DNA strands at the origin of replication will separate,but replication will not progress. 
C) The DNA will supercoil. 
D) DNA polymerase I will not function correctly.

Question 20

A eukaryotic gene has "sticky ends" produced by the restriction endonuclease EcoRI.The gene is added to a mixture containing EcoRI and a bacterial plasmid that carries two genes conferring resistance to the antibiotics ampicillin and tetracycline.The plasmid has one recognition site for EcoRI located in the tetracycline resistance gene.This mixture is incubated for several hours,exposed to DNA ligase,and then added to bacteria growing in nutrient broth.The bacteria are allowed to grow overnight and are streaked on a plate using a technique that produces isolated colonies that are clones of the original.Samples of these colonies are then grown in four different media: nutrient broth plus ampicillin,nutrient broth plus tetracycline,nutrient broth plus ampicillin and tetracycline,and nutrient broth without antibiotics.
Bacteria containing a plasmid into which the eukaryotic gene has been inserted would grow in which of the following conditions?

Accepted Answer

A) in the nutrient broth only 
B) in the nutrient broth and the tetracycline broth only 
C) in the nutrient broth,the ampicillin broth,and the tetracycline broth 
D) in the ampicillin broth and the nutrient broth 
A) in the nutrient broth only 
B) in the nutrient broth and the tetracycline broth only 
C) in the nutrient broth,the ampicillin broth,and the tetracycline broth 
D) in the ampicillin broth and the nutrient broth

Exam 13: The Molecular Basis of Inheritance

Which of the following molecule(s)help(s)to hold the DNA strands apart while they are being replicated?

The segment of DNA shown in the figure above has restriction sites I and II,which create restriction fragments A,B,and C.Which of the gels produced by electrophoresis shown below best represents the separation and identity of these fragments?

In a linear eukaryotic chromatin sample,which of the following strands is looped into nucleosomes?

Which of the following statements describes one difference between DNA replication in prokaryotes and DNA replication in eukaryotes?

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

Which of the following statements correctly describes how the leading and the lagging strands of DNA formed during DNA replication differ?

In E.coli,which of the following enzymes removes the RNA primer from the 5' end of the DNA fragment?

Which of the following statements accurately describes why Taq polymerase is used in PCR?

In his transformation experiments,which of the following results did Griffith observe?

Why does a new DNA strand elongate only in the 5' to 3' direction in replication?

Why is it so important to be able to amplify DNA fragments when studying genes?

Which of the following sets of materials is required by both eukaryotes and prokaryotes for DNA replication?

E.coli cells grown on 15N medium are transferred to 14N medium and allowed to grow for two more generations (two rounds of DNA replication).DNA extracted from these cells is centrifuged.What density distribution of DNA would you expect in this experiment?

In which order do the necessary enzymes act to repair a thymine dimer by nucleotide excision repair?

What is the function of DNA polymerase III in replication in E.coli?

Which of the following statements best describes the eukaryotic chromosome?

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?

Introduction: Evolution and the Foundations of Biology

The Chemical Context of Life

Carbon and the Molecular Diversity of Life

A Tour of the Cell

Membrane Transport and Cell Signaling

An Introduction to Metabolism

Cellular Respiration and Fermentation

Photosynthesis

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

Development,stem Cells,and Cancer

Viruses

Genomes and Their Evolution

Descent With Modification

Phylogeny

The Evolution of Populations

The Origin of Species

Broad Patterns of Evolution

Early Life and the Diversification of Prokaryotes

The Origin and Diversification of Eukaryotes

The Colonization of Land by Plants and Fungi

The Rise of Animal Diversity

Plant Structure and Growth

Resource Acquisition,nutrition,and Transport in Vascular Plants

Reproduction and Domestication of Flowering Plants

Plant Responses to Internal and External Signals

Homeostasis and Endocrine Signaling

Animal Nutrition

Circulation and Gas Exchange

The Immune System

Reproduction and Development

Neurons,synapses,and Signaling

Nervous and Sensory Systems

Motor Mechanisms and Behavior

Population Ecology and the Distribution of Organisms

Ecological Communities

Ecosystems and Energy

Conservation Biology and Global Change

Filters

E.coli cells grown on ¹⁵N medium are transferred to ¹⁴N medium and allowed to grow for two more generations (two rounds of DNA replication).DNA extracted from these cells is centrifuged.What density distribution of DNA would you expect in this experiment?