Question 1

All of the following statements concerning histones are true EXCEPT that they

Accepted Answer

A)  are rich in arginine and lysine. 
B)  are proteins of relatively low molecular weight. 
C)  exhibit known interspecies homologies in their amino acid sequences. 
D)  are noncovalently attached to DNA in stoichiometric amounts. 
E)  exhibit a wide variety of non-homologous molecular structure. 
A)  are rich in arginine and lysine. 
B)  are proteins of relatively low molecular weight. 
C)  exhibit known interspecies homologies in their amino acid sequences. 
D)  are noncovalently attached to DNA in stoichiometric amounts. 
E)  exhibit a wide variety of non-homologous molecular structure. E

Question 2

The nucleosome is the basic repeating unit of chromatin. Which of the following statements concerning nucleosomes is incorrect:

Accepted Answer

A)  nucleosomes have protein cores consisting of an octamer of protein subunits 
B)  a segment of DNA approximately 145 bp long is associated with each nucleosome 
C)  histone H1 contacts the DNA linker segments as they enter and leave the nucleosome 
D)  the DNA in a nucleosome is packed tightly inside the protein core to conserve space in the nucleus and to protect the DNA from damage 
E)  some nucleosomes form over specific regions of DNA in a non_random manner 
A)  nucleosomes have protein cores consisting of an octamer of protein subunits 
B)  a segment of DNA approximately 145 bp long is associated with each nucleosome 
C)  histone H1 contacts the DNA linker segments as they enter and leave the nucleosome 
D)  the DNA in a nucleosome is packed tightly inside the protein core to conserve space in the nucleus and to protect the DNA from damage 
E)  some nucleosomes form over specific regions of DNA in a non_random manner D

Question 3

Which of the following is a nucleoside found exclusively in tRNA?

Accepted Answer

A)  pseudouridine 
B)  uridine 
C)  thymine 
D)  ribose 
E)  adenosine 
A)  pseudouridine 
B)  uridine 
C)  thymine 
D)  ribose 
E)  adenosine A

Question 4

A segment of DNA has the following sequence pTpApCpGpTpGpC-H. Which of the sequences below would represent the complement of this DNA strand? (Note, all sugars are deoxyribose)

Accepted Answer

A)  pApTpGpCpApCpG-H 
B)  pGpCpTpGpCpApTp-H 
C)  pGpCpApCpGpTpA-H 
D)  pTpApCpGpTpGpC-H 
E)  none of the above 
A)  pApTpGpCpApCpG-H 
B)  pGpCpTpGpCpApTp-H 
C)  pGpCpApCpGpTpA-H 
D)  pTpApCpGpTpGpC-H 
E)  none of the above

Question 5

What are the complementary base pairs in DNA?

Accepted Answer

A)  Adenine : Uracil and Guanine : Cytosine 
B)  Adenine : Thymine and Guanine : Uracil 
C)  Adenine : Guanine and Uracil : Cytosine 
D)  Adenine : Thymine and Guanine : Cytosine 
E)  Adenine : Cytosine and Guanine : Thymine 
A)  Adenine : Uracil and Guanine : Cytosine 
B)  Adenine : Thymine and Guanine : Uracil 
C)  Adenine : Guanine and Uracil : Cytosine 
D)  Adenine : Thymine and Guanine : Cytosine 
E)  Adenine : Cytosine and Guanine : Thymine

Question 6

The histones are

Accepted Answer

A)  ribosomal proteins which regulate the function of ribosomes. 
B)  proteins which bind to tRNAs and activate them. 
C)  small basic proteins associated with the DNA molecules in the chromatin of eukaryotic cells. 
D)  small acidic proteins which may be involved in gene regulation. 
E)  proteins required for binding of the mRNA to the ribosome. 
A)  ribosomal proteins which regulate the function of ribosomes. 
B)  proteins which bind to tRNAs and activate them. 
C)  small basic proteins associated with the DNA molecules in the chromatin of eukaryotic cells. 
D)  small acidic proteins which may be involved in gene regulation. 
E)  proteins required for binding of the mRNA to the ribosome.

Question 7

Which of the following classes of RNA contain the largest relative percentage of unusual modified purine and pyrimidine bases?

Accepted Answer

A)  hnRNA 
B)  mRNA 
C)  tRNA 
D)  rRNA 
E)  All contain comparable relative percentages of modified bases. 
A)  hnRNA 
B)  mRNA 
C)  tRNA 
D)  rRNA 
E)  All contain comparable relative percentages of modified bases.

Question 8

In thermal denaturation of double-stranded DNA

Accepted Answer

A)  the phosphodiester bonds undergo hydrolysis. 
B)  the absorption at 260 nm is decreased when the hydrogen-bonded bases become separated. 
C)  G-C pairs are the main contributors towards the hyperchromic effect observed upon thermal denaturation. 
D)  the value of Tm is usually dependent on the G + C content of the DNA. 
E)  the reaction is time and concentration dependent. 
A)  the phosphodiester bonds undergo hydrolysis. 
B)  the absorption at 260 nm is decreased when the hydrogen-bonded bases become separated. 
C)  G-C pairs are the main contributors towards the hyperchromic effect observed upon thermal denaturation. 
D)  the value of Tm is usually dependent on the G + C content of the DNA. 
E)  the reaction is time and concentration dependent.

Question 9

All of the following statements are true concerning the base composition of DNA EXCEPT

Accepted Answer

A)  the base composition is not characteristic of the species. 
B)  the same base composition is present in most cells of the same species. 
C)  the base composition varies widely among different organisms. 
D)  the pyrimidine content equals the purine content. 
E)  the adenine content is equal to the thymine content. 
A)  the base composition is not characteristic of the species. 
B)  the same base composition is present in most cells of the same species. 
C)  the base composition varies widely among different organisms. 
D)  the pyrimidine content equals the purine content. 
E)  the adenine content is equal to the thymine content.

Question 10

What is the main difference between topoisomerases I and II?

Accepted Answer

A)  Gyrases are a subset of topoisomerases I 
B)  Topoisomerase I breaks one strand and II both strands 
C)  Topoisomerase I needs ATP, and II does not 
D)  Topoisomerase II remains bound to DNA until religation 
E)  Topoisomerase relaxes only positively supercoiled species 
A)  Gyrases are a subset of topoisomerases I 
B)  Topoisomerase I breaks one strand and II both strands 
C)  Topoisomerase I needs ATP, and II does not 
D)  Topoisomerase II remains bound to DNA until religation 
E)  Topoisomerase relaxes only positively supercoiled species

Question 11

The H1 histone

Accepted Answer

A)  is one of the four histones in the nucleosome core. 
B)  helps form the octamer nucleosome complex. 
C)  is one of the two arginine-rich histones. 
D)  is present at 1:1 weight ratio with DNA. 
E)  helps fold the bead-on-a-string structure into higher order structures. 
A)  is one of the four histones in the nucleosome core. 
B)  helps form the octamer nucleosome complex. 
C)  is one of the two arginine-rich histones. 
D)  is present at 1:1 weight ratio with DNA. 
E)  helps fold the bead-on-a-string structure into higher order structures.

Question 12

Hyperchromic shift is caused by

Accepted Answer

A)  high GC content. 
B)  high AT content. 
C)  melting of double stranded DNA. 
D)  cooling of double stranded DNA. 
E)  none of the above 
A)  high GC content. 
B)  high AT content. 
C)  melting of double stranded DNA. 
D)  cooling of double stranded DNA. 
E)  none of the above

Question 13

The nucleotide sequence 5'-ATTGCAG-3' should base pair with

Accepted Answer

A)  5'-TAACGTC-3'. 
B)  5'-CTGCAAT-3'. 
C)  3'-ATTGCAG-5'. 
D)  3'-CTGCAAT-5'. 
A)  5'-TAACGTC-3'. 
B)  5'-CTGCAAT-3'. 
C)  3'-ATTGCAG-5'. 
D)  3'-CTGCAAT-5'.

Question 14

Restriction enzymes have all of the following properties EXCEPT

Accepted Answer

A)  they cleave double_stranded DNA. 
B)  they modify DNA by methylation. 
C)  they recognize specific DNA sequences. 
D)  they cleave DNA, producing staggered ends. 
A)  they cleave double_stranded DNA. 
B)  they modify DNA by methylation. 
C)  they recognize specific DNA sequences. 
D)  they cleave DNA, producing staggered ends.

Question 15

Enzymes that catalyze stepwise hydrolysis of mononucleotides from one end of a polynucleotide chain are

Accepted Answer

A)  polymerases. 
B)  endonucleases. 
C)  ligases. 
D)  exonucleases. 
E)  nickases. 
A)  polymerases. 
B)  endonucleases. 
C)  ligases. 
D)  exonucleases. 
E)  nickases.

Question 16

All of the following statements concerning DNA are correct EXCEPT

Accepted Answer

A)  Base-stacking involves the interaction of aromatic pi-electron orbitals and contributes to the stability of the double helix. 
B)  Denatured DNA shows an increased extinction coefficient at 260 nm as compared to double-stranded DNA. 
C)  DNA that is rich in G and C shows a higher melting temperature. 
D)  The nucleotides are joined through glycosidic bonds. 
E)  The two strands have opposite polarity (5'->and >5'). 
A)  Base-stacking involves the interaction of aromatic pi-electron orbitals and contributes to the stability of the double helix. 
B)  Denatured DNA shows an increased extinction coefficient at 260 nm as compared to double-stranded DNA. 
C)  DNA that is rich in G and C shows a higher melting temperature. 
D)  The nucleotides are joined through glycosidic bonds. 
E)  The two strands have opposite polarity (5'->and >5').

Question 17

Each of the following describes tRNA EXCEPT

Accepted Answer

A)  the end terminates in CCA. 
B)  it is synthesized with extra bases on the and 5' ends. 
C)  its extended structure looks like a cloverleaf. 
D)  it furnishes a codon for protein synthesis. 
E)  it has many bases which are modified. 
A)  the end terminates in CCA. 
B)  it is synthesized with extra bases on the and 5' ends. 
C)  its extended structure looks like a cloverleaf. 
D)  it furnishes a codon for protein synthesis. 
E)  it has many bases which are modified.

Question 18

Which of the following observations is part of the evidence supporting the Watson-Crick structure of DNA?

Accepted Answer

A)  In the DNAs examined from a wide variety of sources, the adenine and cytosine contents are equal. 
B)  A non-virulent pneumococcus can be transformed to a virulent strain by the addition of DNA. 
C)  RNA is susceptible to hydrolysis by alkali, whereas DNA is not. 
D)  The sum of the purines present in any double-stranded DNA is equal to the sum of the pyrimidines present. 
A)  In the DNAs examined from a wide variety of sources, the adenine and cytosine contents are equal. 
B)  A non-virulent pneumococcus can be transformed to a virulent strain by the addition of DNA. 
C)  RNA is susceptible to hydrolysis by alkali, whereas DNA is not. 
D)  The sum of the purines present in any double-stranded DNA is equal to the sum of the pyrimidines present.

Question 19

Restriction endonucleases

Accepted Answer

A)  cleave single stranded DNA preferentially. 
B)  cleave DNA at specific sequences only when those sequences are unmethylated. 
C)  remove bases one at a time from the 5' end of the DNA only when the bases are incorrectly matched with the template strand. 
D)  initiate the repair process by making a single endonucleolytic incision at the 5' end of the damaged DNA region. 
E)  are required for the correct processing of tRNA in the cell. 
A)  cleave single stranded DNA preferentially. 
B)  cleave DNA at specific sequences only when those sequences are unmethylated. 
C)  remove bases one at a time from the 5' end of the DNA only when the bases are incorrectly matched with the template strand. 
D)  initiate the repair process by making a single endonucleolytic incision at the 5' end of the damaged DNA region. 
E)  are required for the correct processing of tRNA in the cell.

Question 20

Which of the following statements about supercoiling of DNA are true?
(1) Supercoiled DNA differs in linking number from relaxed DNA.
(2) Supercoiled DNA can be relaxed through the action of topoisomerases.
(3) All DNA in the cell is positively supercoiled.
(4) A negatively supercoiled DNA is more difficult to unwind.

Accepted Answer

A)  Only 2, 3 and 4 are true 
B)  Only 1, 2 and 3 are true 
C)  Only 1 and 3 are true 
D)  Only 1 and 2 are true 
E)  All are true 
A)  Only 2, 3 and 4 are true 
B)  Only 1, 2 and 3 are true 
C)  Only 1 and 3 are true 
D)  Only 1 and 2 are true 
E)  All are true

Exam 2: DNA and RNA: Composition and Structure

All of the following statements concerning histones are true EXCEPT that they

The nucleosome is the basic repeating unit of chromatin. Which of the following statements concerning nucleosomes is incorrect:

Which of the following is a nucleoside found exclusively in tRNA?

A segment of DNA has the following sequence pTpApCpGpTpGpC-H. Which of the sequences below would represent the complement of this DNA strand? (Note, all sugars are deoxyribose)

What are the complementary base pairs in DNA?

The histones are

Which of the following classes of RNA contain the largest relative percentage of unusual modified purine and pyrimidine bases?

In thermal denaturation of double-stranded DNA

All of the following statements are true concerning the base composition of DNA EXCEPT

What is the main difference between topoisomerases I and II?

The H1 histone

Hyperchromic shift is caused by

The nucleotide sequence 5'-ATTGCAG-3' should base pair with

Restriction enzymes have all of the following properties EXCEPT

Enzymes that catalyze stepwise hydrolysis of mononucleotides from one end of a polynucleotide chain are

All of the following statements concerning DNA are correct EXCEPT

Each of the following describes tRNA EXCEPT

Which of the following observations is part of the evidence supporting the Watson-Crick structure of DNA?

Restriction endonucleases

Eukaryotic Cell Structure

Protein I: Composition and Structure

DNA Replication, Recombination, and Repair

RNA: Transcription and Rna Processing

Protein Synthesis: Translation and Posttranslational Modifications

Recombinant Dna and Biotechnology

Regulation of Gene Expression

Protein II: Structure-Function Relationships in Protein Families

Enzymes: Classification, Kinetics, and Control

The Cytochromes P450 and Nitric Oxide Synthases

Biological Membranes: Structure and Membrane Transport

Fundamentals of Signal Transduction

Bioenergetics and Oxidative Metabolism

Carbohydrate Metabolism I: Major Metabolic Pathways and Their Control

Carbohydrate Metabolism II: Special Pathways and Glycoconjugates

Lipid Metabolism I: Synthesis, Storage, and Utilization of Fatty Acids and Triacylglycerols

Lipid Metabolism II: Pathways of Metabolism of Special Lipids

Amino Acid Metabolism

Purine and Pyrimidine Nucleotide Metabolism

Metabolic Interrelationships

Biochemistry of Hormones

Molecular Cell Biology

Cell Cycle, Programmed Cell Death, and Cancer

Digestion and Absorption of Basic Nutritional Constituents

Digestion and Absorption of Basic Nutritional Constituents

Principles of Nutrition I and II

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