WGU BIOCHEMISTRY EXAM (QUESTIONS AND ANSWERS)
DNA replication is semiconservative, meaning that each new duplex has one original (parent) strand and
one new strand. Because the two parent strands are separated during replication and the base pairing is
predictable, each parent strand can serve as a template for the new strand synthesis.
DNA replication is ___________, which allows each of the two strands to serve as a _______ for the new
strands.
b. semiconservative, template
Helicase unwinds the double stranded DNA to allow for replication, but this is not a problem for the DNA
polymerase.
Which of the following enzymes does NOT assist the DNA polymerase on the lagging strand to overcome its two
problems? (Recall that the DNA polymerase can only make DNA in the 5'->3' direction, and it must bind a
double-stranded nucleotide polymer before it can start making its own DNA polymer.)
c. Helicase
Nucleotide excision repair is used to repair deletions, insertions, and helix-distorting lesions, such as
thymine dimers.
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?
c. Nucleotide Excision Repair
Frame shift mutations are a kind of mutations which result from addition of deletion of a nucleotide base
resulting in an altered reading frame and ultimately a different protein, than the one the gene originally
encoded. Frameshift mutations are genetic changes because they alter the DNA sequence, whereas
epigenetic changes do not alter the DNA sequence. Epigenetic changes are modifications to genomic
structure (not sequence) that are caused by the external environment. These environmental factors affect
the overall chromatin structure to allow more or less "access" to the DNA by gene expression machinery to
turn the genes "on" or "off". In other words, epigenetics can alter gene expression without changing the
underlying DNA sequences. The changes may or may not be heritable, depending on the location and
circumstances.
Maternal smoking during pregnancy is hazardous yet common in many places. Many studies have associated
prenatal smoking to unhealthy physical and psychological outcomes for the baby. Researchers know that
maternal smoking affects are epigenetic in nature. Which of the following events can be considered epigenetic in
nature?
,a. Changes in chromatin structure
The genes that produce the A and B antigen proteins can both be expressed independently, and a
heterozygote (someone with both genes) will be produce both A and B proteins - neither will dominate the
other. The is an example of codominance.
Blood type is an example of what type of inheritance?
a. Codominance
If D is the disease-conferring dominant allele and d is the normal allele, the father has the genotype Dd and
the mother's genotype is dd. Each child can only inherit a d allele from their mother, and they have a 50%
chance of inheriting the D allele from their father. As a result, the expected probability that their child will
inherit the disease is 50%.
What is the expected probability that a child will have an autosomal dominant disease if their father is
heterozygous for the allele and their mother is homozygous for the normal allele?
a. 50%
The correct answer is incomplete dominance. The blending of the large and small lip protrusion into an
intermediate, medium lip protrusion, as well as the presence of all three variations in the offspring,
demonstrate a clear example of incomplete dominance.
The physical trait of lip protrusion exhibits a characteristic type of inheritance, as shown by the pedigree above.
What type of inheritance best describes this inheritance pattern?
a. Incomplete dominance
Silent mutations are those in which the amino acid encoded doesn't change as a result of the mutation.
Missense mutations are those in which the amino acid encoded changes to a different amino acid as a
result of the mutation.
Nonsense mutations are those in which the amino acid encoded changes to a stop codon as a result of the
mutation, yielding a smaller protein.
Insertions are the inclusion of extra nucleotides compared to the original sequence. They can result in
other mutations, such as nonsense mutations.
Deletions are the removal of nucleotides compared to the original sequence. They can result in other
mutations, such as nonsense mutations.
, The normal sequence of a section of the HLA-B27 gene, a genetic marker of the inflammatory disease
Ankylosing spondylitis, is given below. Match each mutation of the sequence to the type of mutation it exhibits. A
genetic code table is provided for your use in answering the question.
5'- CGG CAG AAU UUA -3'
5'- CAG CAG AAU UUA -3' - Missense mutation
5'- CGG CAG AAA UUU A-3' - Insertion
5'- CGG CAG AAC UUA -3' - Silent mutation
5'- CGG CAG AAU UA -3' - Deletion
5'- CGG UAG AAU UUA-3' - Nonsense mutation
PCR's ability to amplify is powerful, and products can even be generated from samples with just a few
cells. PCR is less reliable for amplifying large segments of DNA greater than 6 kb, though some careful
changes to the techniques can allow it.
PCR is a powerful tool that can do all of the following....
b. detect mutations that lead to disease
c. copy small segments of DNA, less than 6kb
d. amplify DNA from samples that have just a few cells
The primers used in PCR are made from DNA, rather than RNA. RNA primers are used in DNA replication
inside the cell, but the quick degradation of RNA makes it less useful for PCR reactions. Instead, PCR
reactions contain primers made of DNA to anneal to the region of DNA that will be amplified and serve as a
starting point for DNA polymerase.
Which of the following is a required "ingredient" in a PCR
reaction?
a. DNA nucleotides
b. DNA primers
c. DNA polymerase
Differences in DNA sequence can be detected since these changes can alter the ability of primers to anneal
to the DNA. They can also be detected by DNA sequencing of the PCR product. Epigenetic changes are not
detectable via PCR because they don't affect the DNA sequence.
Which of the following changes can be detected using PCR?
a. Differences in DNA sequence
DNA replication is semiconservative, meaning that each new duplex has one original (parent) strand and
one new strand. Because the two parent strands are separated during replication and the base pairing is
predictable, each parent strand can serve as a template for the new strand synthesis.
DNA replication is ___________, which allows each of the two strands to serve as a _______ for the new
strands.
b. semiconservative, template
Helicase unwinds the double stranded DNA to allow for replication, but this is not a problem for the DNA
polymerase.
Which of the following enzymes does NOT assist the DNA polymerase on the lagging strand to overcome its two
problems? (Recall that the DNA polymerase can only make DNA in the 5'->3' direction, and it must bind a
double-stranded nucleotide polymer before it can start making its own DNA polymer.)
c. Helicase
Nucleotide excision repair is used to repair deletions, insertions, and helix-distorting lesions, such as
thymine dimers.
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?
c. Nucleotide Excision Repair
Frame shift mutations are a kind of mutations which result from addition of deletion of a nucleotide base
resulting in an altered reading frame and ultimately a different protein, than the one the gene originally
encoded. Frameshift mutations are genetic changes because they alter the DNA sequence, whereas
epigenetic changes do not alter the DNA sequence. Epigenetic changes are modifications to genomic
structure (not sequence) that are caused by the external environment. These environmental factors affect
the overall chromatin structure to allow more or less "access" to the DNA by gene expression machinery to
turn the genes "on" or "off". In other words, epigenetics can alter gene expression without changing the
underlying DNA sequences. The changes may or may not be heritable, depending on the location and
circumstances.
Maternal smoking during pregnancy is hazardous yet common in many places. Many studies have associated
prenatal smoking to unhealthy physical and psychological outcomes for the baby. Researchers know that
maternal smoking affects are epigenetic in nature. Which of the following events can be considered epigenetic in
nature?
,a. Changes in chromatin structure
The genes that produce the A and B antigen proteins can both be expressed independently, and a
heterozygote (someone with both genes) will be produce both A and B proteins - neither will dominate the
other. The is an example of codominance.
Blood type is an example of what type of inheritance?
a. Codominance
If D is the disease-conferring dominant allele and d is the normal allele, the father has the genotype Dd and
the mother's genotype is dd. Each child can only inherit a d allele from their mother, and they have a 50%
chance of inheriting the D allele from their father. As a result, the expected probability that their child will
inherit the disease is 50%.
What is the expected probability that a child will have an autosomal dominant disease if their father is
heterozygous for the allele and their mother is homozygous for the normal allele?
a. 50%
The correct answer is incomplete dominance. The blending of the large and small lip protrusion into an
intermediate, medium lip protrusion, as well as the presence of all three variations in the offspring,
demonstrate a clear example of incomplete dominance.
The physical trait of lip protrusion exhibits a characteristic type of inheritance, as shown by the pedigree above.
What type of inheritance best describes this inheritance pattern?
a. Incomplete dominance
Silent mutations are those in which the amino acid encoded doesn't change as a result of the mutation.
Missense mutations are those in which the amino acid encoded changes to a different amino acid as a
result of the mutation.
Nonsense mutations are those in which the amino acid encoded changes to a stop codon as a result of the
mutation, yielding a smaller protein.
Insertions are the inclusion of extra nucleotides compared to the original sequence. They can result in
other mutations, such as nonsense mutations.
Deletions are the removal of nucleotides compared to the original sequence. They can result in other
mutations, such as nonsense mutations.
, The normal sequence of a section of the HLA-B27 gene, a genetic marker of the inflammatory disease
Ankylosing spondylitis, is given below. Match each mutation of the sequence to the type of mutation it exhibits. A
genetic code table is provided for your use in answering the question.
5'- CGG CAG AAU UUA -3'
5'- CAG CAG AAU UUA -3' - Missense mutation
5'- CGG CAG AAA UUU A-3' - Insertion
5'- CGG CAG AAC UUA -3' - Silent mutation
5'- CGG CAG AAU UA -3' - Deletion
5'- CGG UAG AAU UUA-3' - Nonsense mutation
PCR's ability to amplify is powerful, and products can even be generated from samples with just a few
cells. PCR is less reliable for amplifying large segments of DNA greater than 6 kb, though some careful
changes to the techniques can allow it.
PCR is a powerful tool that can do all of the following....
b. detect mutations that lead to disease
c. copy small segments of DNA, less than 6kb
d. amplify DNA from samples that have just a few cells
The primers used in PCR are made from DNA, rather than RNA. RNA primers are used in DNA replication
inside the cell, but the quick degradation of RNA makes it less useful for PCR reactions. Instead, PCR
reactions contain primers made of DNA to anneal to the region of DNA that will be amplified and serve as a
starting point for DNA polymerase.
Which of the following is a required "ingredient" in a PCR
reaction?
a. DNA nucleotides
b. DNA primers
c. DNA polymerase
Differences in DNA sequence can be detected since these changes can alter the ability of primers to anneal
to the DNA. They can also be detected by DNA sequencing of the PCR product. Epigenetic changes are not
detectable via PCR because they don't affect the DNA sequence.
Which of the following changes can be detected using PCR?
a. Differences in DNA sequence
