WGU BIOCHEMISTRY OA EVALUATION EXAMS
UPDATED QUESTIONS AND ANSWERS SURE A+
✔✔Homologous recombination:
1. Fixes single damaged nucleotides
2. Repairs a broken chromsome using genetic information from same chromosome
inherited from other parent.
3. Fixes mistakes made by DNA polymerase during DNA replication
4. Fixes multiple damaged nucleotides - ✔✔2. Repairs a broken chromsome using
genetic information from same chromosome inherited from other parent.
Feedback
Correct! Homologous refers to the pair of same chromosomes (same genes in same
order, except different alleles) you inherit from each parent - for example, the two
chromosome 12s in your cells, one from your mother and one from your father.
Homologous recombination fixes broken chromosomes using DNA in the same position
on the homologous chromosome as a template to fix the broken chromosome.
Homologous recombination also shuffles DNA between the pair of chromosomes
adding genetic variation.
✔✔When the wrong nucleotide is added to a newly forming DNA strand during DNA
replication
,1. Distortion of the double helix structure occurs because of uncomplimentary pairing of
the nucleotides
2. The DNA can not be repaired
3. The cell dies
4. Thymine dimers occur - ✔✔1. Distortion of the double helix structure occurs because
of uncomplimentary pairing of the nucleotides
Feedback
Correct! A mismatch (A with C or G, T with C or G) causes a bump to form in the DNA
double helix, which is recognized by proofreading enzymes and fixed by excision repair.
✔✔A patient with xeroderma pigmentosum is prone to developing multiple skin cancers
starting in childhood. This occurs because of a mutation in a gene that codes for
enzymes that help repair DNA damage through the nucleotide excision repair (NER)
pathways. How does NER differ from other repair mechanisms? In NER:
a. Only one nucleotide is removed and DNA polymerase replaces the one abnormality
b. The error in one strand of DNA is removed as well as several nucleotides on either
side of the error. The gap that was removed is filled in by DNA polymerase
c. The entire homologous chromosome is used to repair the double stranded DNA error
d. The affected DNA strand and its complementary strand is discarded and a new
double stranded DNA is created - ✔✔b. The error in one strand of DNA is removed as
well as several nucleotides on either side of the error. The gap that was removed is
filled in by DNA polymerase
Feedback
Correct! Nucleotide excision repair replaces several damaged nucleotides plus
additional nucleotides and uses the DNA on the opposite strand as a template to fill in
the gap.
✔✔Which of the following is NOT a step in base excision repair?
a. Ligation to restore continuity of the DNA backbone
b. Synthesis of an RNA primer
c. Recognition of the damage
d. Removal of the damage by excising part of one strand to leave a gap - ✔✔b.
Synthesis of an RNA primer
Feedback
Synthesis of an RNA primer is part of DNA replication, not DNA repair.
✔✔Several components of cigarette smoke, including benzopyrene, insert themselves
(intercalate) into the DNA and lead to several types of mutations such as frameshift
mutations, including both insertions and deletion. Which of the following repair pathways
would be used to repair this type of damage?
,Base excision repair
Mismatch Repair
Nucleotide Excision Repair
Homologous Recombination - ✔✔Nucleotide Excision Repair
Feedback
Correct! Nucleotide excision repair is used to repair deletions, insertions, and helix-
distorting lesions, such as thymine dimers.
✔✔What is the proper order of the steps involved in excision repair?
1. Recognize the damage, resynthesize the sequence, remove the damage, ligate the
DNA backbone.
2. Recognize the damage, remove the damage, resynthesize the sequence, ligate the
DNA backbone.
3. Recognize the damage, remove the damage, ligate the DNA backbone, resynthesize
the sequence.
4. Recognize the damage, ligate the DNA backbone, remove the damage, resynthesize
the sequence. - ✔✔2. Recognize the damage, remove the damage, resynthesize the
sequence, ligate the DNA backbone.
Feedback
Correct! The basic steps of excision repair are given as bullet points at the very
beginning of Lesson 1: DNA and RNA; Chapter - Inheritance of Genes; Subchapter -
DNA Damage and Repair; Section - Excision Repair Corrects The Most Frequent DNA
Lesions.
✔✔Which of the following best describes the nature of protein primary structure?
1. Structural elements such as alpha helices and beta pleated sheets
2. Amino acids linked together in a specific order by peptide bonds
3. Two or more polypeptide chains coming together to form the final functional protein
4. The overall three-dimensional shape of a chain of amino acids - ✔✔2. Amino acids
linked together in a specific order by peptide bonds
Feedback
Correct! The sequence of amino acids connected by peptide bonds in a specific order
defines protein primary structure.
"Structural elements such as alpha helices and beta pleated sheets" refers to secondary
structure.
"The overall three-dimensional shape of a chain of amino acids" refers to tertiary
structure.
, "Two or more polypeptide chains coming together to form the final functional protein"
refers to quaternary structure.
✔✔Which of the following statements about the different levels of protein structure is
true?
1. Two or more polypeptides each with their own secondary structures come together to
form a single larger tertiary structure of a protein
2. Peptide bonds between amino acids make up the secondary structure of a protein
3. The interactions between the side chains of the amino acids make up the secondary
level structure of a protein
4. The interactions between the side chains of the amino acids make up the tertiary
level structure of a protein - ✔✔4. The interactions between the side chains of the
amino acids make up the tertiary level structure of a protein
Feedback
Correct! The interactions between the side chains of the amino acids make up the
tertiary level structure of a protein.
✔✔3. Which type of bonding or interaction is correctly paired with a chemical or change
in environment that will disrupt/break the interaction or bond?
Peptide bonds: Reducing agents
Hydrophobic interactions: Change in pH
Peptide bonds: Change in pH
Hydrogen bonds/ionic bonds: Change in pH - ✔✔Hydrogen bonds/ionic bonds: Change
in pH
Feedback
Correct! Hydrogen bonds and ionic bonds can be disrupted by changes in pH. High salt
concentrations can also disrupt ionic bonds / hydrogen bonds, heat disrupts
hydrophobic interactions, and reducing agents disrupt sulfide bonds.
✔✔Which of the following statements about protein structure and stability is true?
1. Denaturation is the loss of primary, secondary, and tertiary structure
2. Denatured proteins retain their tertiary structure
3. Ionic bonds between the side chains of the charged amino acids stabilize the protein
structure
4. Protein structure is not stabilized by the hydrophobic effect - ✔✔3. Ionic bonds
between the side chains of the charged amino acids stabilize the protein structure
Feedback
Correct! Ionic bonds help stabilize both the tertiary structure of a protein chain and the
quaternary structure of a protein with multiple subunits.
UPDATED QUESTIONS AND ANSWERS SURE A+
✔✔Homologous recombination:
1. Fixes single damaged nucleotides
2. Repairs a broken chromsome using genetic information from same chromosome
inherited from other parent.
3. Fixes mistakes made by DNA polymerase during DNA replication
4. Fixes multiple damaged nucleotides - ✔✔2. Repairs a broken chromsome using
genetic information from same chromosome inherited from other parent.
Feedback
Correct! Homologous refers to the pair of same chromosomes (same genes in same
order, except different alleles) you inherit from each parent - for example, the two
chromosome 12s in your cells, one from your mother and one from your father.
Homologous recombination fixes broken chromosomes using DNA in the same position
on the homologous chromosome as a template to fix the broken chromosome.
Homologous recombination also shuffles DNA between the pair of chromosomes
adding genetic variation.
✔✔When the wrong nucleotide is added to a newly forming DNA strand during DNA
replication
,1. Distortion of the double helix structure occurs because of uncomplimentary pairing of
the nucleotides
2. The DNA can not be repaired
3. The cell dies
4. Thymine dimers occur - ✔✔1. Distortion of the double helix structure occurs because
of uncomplimentary pairing of the nucleotides
Feedback
Correct! A mismatch (A with C or G, T with C or G) causes a bump to form in the DNA
double helix, which is recognized by proofreading enzymes and fixed by excision repair.
✔✔A patient with xeroderma pigmentosum is prone to developing multiple skin cancers
starting in childhood. This occurs because of a mutation in a gene that codes for
enzymes that help repair DNA damage through the nucleotide excision repair (NER)
pathways. How does NER differ from other repair mechanisms? In NER:
a. Only one nucleotide is removed and DNA polymerase replaces the one abnormality
b. The error in one strand of DNA is removed as well as several nucleotides on either
side of the error. The gap that was removed is filled in by DNA polymerase
c. The entire homologous chromosome is used to repair the double stranded DNA error
d. The affected DNA strand and its complementary strand is discarded and a new
double stranded DNA is created - ✔✔b. The error in one strand of DNA is removed as
well as several nucleotides on either side of the error. The gap that was removed is
filled in by DNA polymerase
Feedback
Correct! Nucleotide excision repair replaces several damaged nucleotides plus
additional nucleotides and uses the DNA on the opposite strand as a template to fill in
the gap.
✔✔Which of the following is NOT a step in base excision repair?
a. Ligation to restore continuity of the DNA backbone
b. Synthesis of an RNA primer
c. Recognition of the damage
d. Removal of the damage by excising part of one strand to leave a gap - ✔✔b.
Synthesis of an RNA primer
Feedback
Synthesis of an RNA primer is part of DNA replication, not DNA repair.
✔✔Several components of cigarette smoke, including benzopyrene, insert themselves
(intercalate) into the DNA and lead to several types of mutations such as frameshift
mutations, including both insertions and deletion. Which of the following repair pathways
would be used to repair this type of damage?
,Base excision repair
Mismatch Repair
Nucleotide Excision Repair
Homologous Recombination - ✔✔Nucleotide Excision Repair
Feedback
Correct! Nucleotide excision repair is used to repair deletions, insertions, and helix-
distorting lesions, such as thymine dimers.
✔✔What is the proper order of the steps involved in excision repair?
1. Recognize the damage, resynthesize the sequence, remove the damage, ligate the
DNA backbone.
2. Recognize the damage, remove the damage, resynthesize the sequence, ligate the
DNA backbone.
3. Recognize the damage, remove the damage, ligate the DNA backbone, resynthesize
the sequence.
4. Recognize the damage, ligate the DNA backbone, remove the damage, resynthesize
the sequence. - ✔✔2. Recognize the damage, remove the damage, resynthesize the
sequence, ligate the DNA backbone.
Feedback
Correct! The basic steps of excision repair are given as bullet points at the very
beginning of Lesson 1: DNA and RNA; Chapter - Inheritance of Genes; Subchapter -
DNA Damage and Repair; Section - Excision Repair Corrects The Most Frequent DNA
Lesions.
✔✔Which of the following best describes the nature of protein primary structure?
1. Structural elements such as alpha helices and beta pleated sheets
2. Amino acids linked together in a specific order by peptide bonds
3. Two or more polypeptide chains coming together to form the final functional protein
4. The overall three-dimensional shape of a chain of amino acids - ✔✔2. Amino acids
linked together in a specific order by peptide bonds
Feedback
Correct! The sequence of amino acids connected by peptide bonds in a specific order
defines protein primary structure.
"Structural elements such as alpha helices and beta pleated sheets" refers to secondary
structure.
"The overall three-dimensional shape of a chain of amino acids" refers to tertiary
structure.
, "Two or more polypeptide chains coming together to form the final functional protein"
refers to quaternary structure.
✔✔Which of the following statements about the different levels of protein structure is
true?
1. Two or more polypeptides each with their own secondary structures come together to
form a single larger tertiary structure of a protein
2. Peptide bonds between amino acids make up the secondary structure of a protein
3. The interactions between the side chains of the amino acids make up the secondary
level structure of a protein
4. The interactions between the side chains of the amino acids make up the tertiary
level structure of a protein - ✔✔4. The interactions between the side chains of the
amino acids make up the tertiary level structure of a protein
Feedback
Correct! The interactions between the side chains of the amino acids make up the
tertiary level structure of a protein.
✔✔3. Which type of bonding or interaction is correctly paired with a chemical or change
in environment that will disrupt/break the interaction or bond?
Peptide bonds: Reducing agents
Hydrophobic interactions: Change in pH
Peptide bonds: Change in pH
Hydrogen bonds/ionic bonds: Change in pH - ✔✔Hydrogen bonds/ionic bonds: Change
in pH
Feedback
Correct! Hydrogen bonds and ionic bonds can be disrupted by changes in pH. High salt
concentrations can also disrupt ionic bonds / hydrogen bonds, heat disrupts
hydrophobic interactions, and reducing agents disrupt sulfide bonds.
✔✔Which of the following statements about protein structure and stability is true?
1. Denaturation is the loss of primary, secondary, and tertiary structure
2. Denatured proteins retain their tertiary structure
3. Ionic bonds between the side chains of the charged amino acids stabilize the protein
structure
4. Protein structure is not stabilized by the hydrophobic effect - ✔✔3. Ionic bonds
between the side chains of the charged amino acids stabilize the protein structure
Feedback
Correct! Ionic bonds help stabilize both the tertiary structure of a protein chain and the
quaternary structure of a protein with multiple subunits.
