Question 1

Outline the key steps that occur during meiosis in animal germ-line cells.

Accepted Answer

The chromosomes of a diploid cell are du

Question 2

In the bacterial cell,what are catenated chromosomes,when do they arise,and how does the cell resolve the problem posed by their structure?

Accepted Answer

Catenanes are topologically interlinked

Question 3

Which of the following is false about transposition of DNA?

Accepted Answer

A) The diversity of immunoglobins is in part due to DNA recombination by transposition. 
B) Transposition occurs in both prokaryotes and eukaryotes. 
C) Enzymes are not required for transposition. 
D) The first step of transposition can be single- or double-stranded DNA cleavage. 
E) Transposition can lead to simple movement of a DNA region or duplication of that region in a new location. 
A) The diversity of immunoglobins is in part due to DNA recombination by transposition. 
B) Transposition occurs in both prokaryotes and eukaryotes. 
C) Enzymes are not required for transposition. 
D) The first step of transposition can be single- or double-stranded DNA cleavage. 
E) Transposition can lead to simple movement of a DNA region or duplication of that region in a new location.

Question 4

All known DNA polymerases can only elongate a preexisting DNA chain (i.e. ,require a primer)but cannot initiate a new DNA chain.Nevertheless,during semiconservative DNA replication in the cell,entirely new daughter DNA chains are synthesized.Explain the process that occurs in the cell that allows for the synthesis of daughter chains by DNA polymerase.

Accepted Answer

In the cell,initiation of DNA chains occ

Question 5

What is an Okazaki fragment? What enzyme(s)is (are)required for its formation in E.coli?

Accepted Answer

An Okazaki fragment is an intermediate i

Question 6

Explain how inheriting mutations in genes encoding DNA repair enzymes could lead to increased cancer risk.

Accepted Answer

Mutations in DNA repair genes

Question 7

In contrast to bacteria,eukaryotic chromosomes need multiple DNA replication origins because:

Accepted Answer

A) eukaryotic chromosomes cannot usually replicate bidirectionally. 
B) eukaryotic genomes are not usually circular,like the bacterial chromosome is. 
C) the processivity of the eukaryotic DNA polymerase is much less than the bacterial enzyme. 
D) their replication rate is much slower,and it would take too long with only a single origin per chromosome. 
E) they have a variety of DNA polymerases for different purposes,and need a corresponding variety of replication origins. 
A) eukaryotic chromosomes cannot usually replicate bidirectionally. 
B) eukaryotic genomes are not usually circular,like the bacterial chromosome is. 
C) the processivity of the eukaryotic DNA polymerase is much less than the bacterial enzyme. 
D) their replication rate is much slower,and it would take too long with only a single origin per chromosome. 
E) they have a variety of DNA polymerases for different purposes,and need a corresponding variety of replication origins.

Question 8

Which mechanism is used to repair a chemically modified base in DNA?

Accepted Answer

A) Mismatch repair 
B) Base-excision repair 
C) Nucleotide-excision repair 
D) Direct repair 
E) More than one is used for this type of lesion 
A) Mismatch repair 
B) Base-excision repair 
C) Nucleotide-excision repair 
D) Direct repair 
E) More than one is used for this type of lesion

Question 9

What distinguishes the two mechanistic pathways for transposition in bacteria,and what is a cointegrate?

Accepted Answer

Direct transposition moves the transposo

Question 10

DNA replication in E.coli begins at a site in the DNA called the (a)___________.At the replication fork the (b)___________ strand is synthesized continuously while the (c)_________ strand is synthesized discontinuously.On the strand synthesized discontinuously,the short pieces are called (d)____________ fragments.An RNA primer for each of the fragments is synthesized by an enzyme called (e)__________,and this RNA primer is removed after the fragment is synthesized by the enzyme (f)___________,using its (g)_____________ activity.The nicks left behind in this process are sealed by the enzyme (h)_____________.

Accepted Answer

(a)origin; 
(b)leading; 
(c)la

Question 11

The Ames test is used to:

Accepted Answer

A) detect bacterial viruses. 
B) determine the rate of DNA replication. 
C) examine the potency of antibiotics. 
D) measure the mutagenic effects of various chemical compounds. 
E) quantify the damaging effects of UV light on DNA molecules. 
A) detect bacterial viruses. 
B) determine the rate of DNA replication. 
C) examine the potency of antibiotics. 
D) measure the mutagenic effects of various chemical compounds. 
E) quantify the damaging effects of UV light on DNA molecules.

Question 12

The function of the eukaryotic DNA replication factor PCNA (proliferating cell nuclear antigen)is similar to that of the $\beta$-subunit of bacterial DNA polymerase III in that it:

Accepted Answer

A) facilitates replication of telomeres. 
B) forms a circular sliding clamp to increase the processivity of replication. 
C) has a 3' $\rightarrow$  5' proofreading activity. 
D) increases the speed but not the processivity of the replication complex. 
E) participates in DNA repair. 
A) facilitates replication of telomeres. 
B) forms a circular sliding clamp to increase the processivity of replication. 
C) has a 3' $\rightarrow$  5' proofreading activity. 
D) increases the speed but not the processivity of the replication complex. 
E) participates in DNA repair.

Question 13

Nucleotide polymerization appears to be a thermodynamically balanced reaction (because one phosphodiester bond is broken and one is formed).Nevertheless,the reaction proceeds efficiently both in a test tube and in the cell.Explain.

Accepted Answer

Base-stacking and base-pairing interacti

Question 14

Describe briefly how equilibrium density gradient centrifugation was used to demonstrate that DNA replication in E.coli is semiconservative.

Accepted Answer

Equilibrium density gradient centrifugat

Question 15

When bacterial DNA replication introduces a mismatch in a double-stranded DNA,the methyl-directed repair system:

Accepted Answer

A) cannot distinguish the template strand from the newly replicated strand. 
B) changes both the template strand and the newly replicated strand. 
C) corrects the DNA strand that is methylated. 
D) corrects the mismatch by changing the newly replicated strand. 
E) corrects the mismatch by changing the template strand. 
A) cannot distinguish the template strand from the newly replicated strand. 
B) changes both the template strand and the newly replicated strand. 
C) corrects the DNA strand that is methylated. 
D) corrects the mismatch by changing the newly replicated strand. 
E) corrects the mismatch by changing the template strand.

Question 16

List two proteins or enzymes,other than DNA polymerase III,that are found at the replication fork in E.coli.Describe each of their functions with no more than one sentence.

Accepted Answer

The proteins are listed in Table 25-4.Th

Question 17

In homologous recombination in E.coli,the protein that moves along a double-stranded DNA,unwinding the strands ahead of it and degrading them,is:

Accepted Answer

A) chi. 
B) DNA ligase. 
C) RecA protein. 
D) RecBCD enzyme. 
E) RuvC protein (resolvase). 
A) chi. 
B) DNA ligase. 
C) RecA protein. 
D) RecBCD enzyme. 
E) RuvC protein (resolvase).

Question 18

Which of these enzymes is not directly involved in methyl-directed mismatch repair in E.coli?

Accepted Answer

A) DNA glycosylase 
B) DNA helicase II 
C) DNA ligase 
D) DNA polymerase III 
E) Exonuclease I 
A) DNA glycosylase 
B) DNA helicase II 
C) DNA ligase 
D) DNA polymerase III 
E) Exonuclease I

Question 19

Explain the role of DNA glycosylases in DNA repair.

Accepted Answer

When spontaneous deamination converts cy

Question 20

The ABC excinuclease is essential in:

Accepted Answer

A) base-excision repair. 
B) methyl-directed repair. 
C) mismatch repair. 
D) nucleotide-excision repair. 
E) SOS repair. 
A) base-excision repair. 
B) methyl-directed repair. 
C) mismatch repair. 
D) nucleotide-excision repair. 
E) SOS repair.

Exam 25: Dna Metabolism

Outline the key steps that occur during meiosis in animal germ-line cells.

In the bacterial cell,what are catenated chromosomes,when do they arise,and how does the cell resolve the problem posed by their structure?

Which of the following is false about transposition of DNA?

What is an Okazaki fragment? What enzyme(s)is (are)required for its formation in E.coli?

Explain how inheriting mutations in genes encoding DNA repair enzymes could lead to increased cancer risk.

In contrast to bacteria,eukaryotic chromosomes need multiple DNA replication origins because:

Which mechanism is used to repair a chemically modified base in DNA?

What distinguishes the two mechanistic pathways for transposition in bacteria,and what is a cointegrate?

The Ames test is used to:

The function of the eukaryotic DNA replication factor PCNA (proliferating cell nuclear antigen)is similar to that of the β\betaβ -subunit of bacterial DNA polymerase III in that it:

Nucleotide polymerization appears to be a thermodynamically balanced reaction (because one phosphodiester bond is broken and one is formed).Nevertheless,the reaction proceeds efficiently both in a test tube and in the cell.Explain.

Describe briefly how equilibrium density gradient centrifugation was used to demonstrate that DNA replication in E.coli is semiconservative.

When bacterial DNA replication introduces a mismatch in a double-stranded DNA,the methyl-directed repair system:

List two proteins or enzymes,other than DNA polymerase III,that are found at the replication fork in E.coli.Describe each of their functions with no more than one sentence.

In homologous recombination in E.coli,the protein that moves along a double-stranded DNA,unwinding the strands ahead of it and degrading them,is:

Which of these enzymes is not directly involved in methyl-directed mismatch repair in E.coli?

Explain the role of DNA glycosylases in DNA repair.

The ABC excinuclease is essential in:

The Foundations of Biochemistry

Water

Amino Acids, peptides, and Proteins

The Three-Dimensional Structure of Proteins

Protein Function

Enzymes

Carbohydrates and Glycobiology

Nucleotides and Nucleic Acids

Recombinant Dna Technology

Lipids

Biological Membranes and Transport

Biosignaling

Principles of Bioenergetics

Glycolysis, gluconeogenesis, and the Pentose Phosphate Pathway

Principles of Metabolic Regulation

The Citric Acid Cycle

Fatty Acid Catabolism

Amino Acid Oxidation and the Production of Urea

Oxidative Phosphorylation and Photophosphorylation

Carbohydrate Biosynthesis in Plants and Bacteria

Lipid Biosynthesis

Biosynthesis of Amino Acids, nucleotides, and Related Molecules

Integration and Hormonal Regulation of Mammalian Metabolism

Genes and Chromosomes

Rna Metabolism

Protein Metabolism

Regulation of Gene Expression

Filters

The function of the eukaryotic DNA replication factor PCNA (proliferating cell nuclear antigen)is similar to that of the $\beta$ -subunit of bacterial DNA polymerase III in that it: