MCAT The Princeton Review AAMC Practice
Exam 1 - Biological and Biochemical
Foundations of Living Systems
Question 1
Passage 1 (Questions 1 - 6)
Correct Answer
About 15% of colorectal cancers (CRCs), or colon cancers, are caused by defects in
the mismatch repair system (MMR) that corrects certain DNA replication errors. In
some cases, this MMR defect contributes to microsatellite instability (MSI), which is
characterized by genetic hypermutability in DNA microsatellites (small repeated
sequences that occur throughout the genome).
Researchers studying MSI in CRC cell lines and primary tumors observed that 100%
of those analyzed contained deletions of 3 to 8 base pairs in the 17-thymine
nucleotide microsatellite (T17) located in Intron 8 of the gene encoding heat shock
protein 110 (HSP110). HSP110 can bind structurally similar heat shock proteins and
functions to facilitate proper protein folding and to reduce levels of nonfunctional
protein aggregates. The larger HSP110 T17 deletions cause Exon 9 to be omitted
from the final sequence during pre-mRNA processing. This generates a premature
stop codon in Exon 10, resulting in the mutant protein HSP110ΔE9. People with MSI
CRC have HSP110ΔE9 transcripts in cancerous tissue only.
Table 1 shows, with respect to T17-deletion size, the amount of HSP110ΔE9 mRNA
expressed relative to the total amount of HSP110 mRNA expressed in MSI CRC
primary tumor cells. The total amount of HSP110 mRNA expressed includes both
wild-type HSP110 (HSP110WT) and HSP110ΔE9 mRNA.
Page 1 of 69
,Question 2
1. Based on the data presented in the passage, which statement best describes the
HSP110ΔE9 allele?
A. Cancer-promoting and dominant to HSP110WT
B. Cancer-promoting and recessive to HSP110WT
C. Cancer-suppressing and dominant to HSP110WT
D. Cancer-suppressing and recessive to HSP110WT
Correct Answer
Answer:
C. Cancer-suppressing and dominant to HSP110WT
Reasoning:
A. Based on Figure 1, expression of HSP110ΔE9 results in reduced, not increased,
tumorigenicity. Thus, HSP110ΔE9 expression suppresses, it does not promote,
cancer.
B. Based on Figure 1, HSP110ΔE9 expression suppresses, it does not promote,
cancer. Furthermore, based on Table 2, HSP110ΔE9 expression is dominant, not
recessive, to HSP110 because it counteracts HSP110Δ activity in protein
aggregation.
C. Figure 1 shows that HSP110ΔE9 expressing cells have a reduced tumor
growth when injected in other mice. Based on Table 2, HSP110ΔE9 counteracts
the effects of HSP110 on protein aggregation and stimulates apoptosis, thus
HSP110ΔE9 expression is dominant to HSP110.
D. Based on Figure 1, HSP110ΔE9 expression is cancer-suppressing; however, the
effects of HSP110ΔE9 are dominant, and not recessive, to HSP110 because
HSP110ΔE9 is able to counteract the effects of HSP110 and stimulate apoptosis.
Page 2 of 69
,Question 3
2. Based on the passage, in MSI CRC primary tumor cells, the size of the deletion in
the HSP110 T17 microsatellite is inversely correlated with:
A. the amount of HSP110ΔE9 protein expressed.
B. the number of mature HSP110WT transcripts synthesized.
C. the frequency of the omission of HSP110 Exon 9 during splicing.
D. the extent of premature translation termination in Exon 10.
Correct Answer
Answer:
B. The number of mature HSP110WT transcripts synthesized
Reasoning:
A. The passage does not report protein levels for HSP110 or HSP110ΔE9.
B. Table 1 shows that as the number of deleted base pairs (bp) increases from
3 to 8, the levels of HSP110ΔE9 increase whereas the levels of HSP110
decrease. This data indicates that there is an inverse relationship between the
number of deleted bps and HSP110 levels.
C. The passage does not show a frequency of E9 omissions. It only indicates that the
larger omission results in deletion of E9.
D. The passage does not show the extent of premature translation termination, but
only the levels of HSP110ΔE9 and HSP110 transcripts (mRNA).
Page 3 of 69
, Question 4
A man with a CRC mutation that results in the synthesis of HSP110ΔE9 and a woman
that does not carry this mutation in any of her tissues have a child. What is the
percent chance that the child will inherit the CRC mutation?
A. 0%
B. 25%
C. 50%
D. 100%
Correct Answer
Answer:
A. 0%
Reasoning:
A. Based on the passage, HSP110ΔE9 is only expressed in somatic cells, not
germline. Thus, it cannot be inherited.
B. The passage indicates that HSP110ΔE9 is only expressed in cancerous cells;
therefore, it cannot be inherited.
C. As the transcripts are only expressed in cancerous cells, the mutation will not be
inherited.
D. The child is not likely to inherit the mutation because, based on the passage,
HSPΔE9 is only expressed in cancerous cells.
Page 4 of 69
Exam 1 - Biological and Biochemical
Foundations of Living Systems
Question 1
Passage 1 (Questions 1 - 6)
Correct Answer
About 15% of colorectal cancers (CRCs), or colon cancers, are caused by defects in
the mismatch repair system (MMR) that corrects certain DNA replication errors. In
some cases, this MMR defect contributes to microsatellite instability (MSI), which is
characterized by genetic hypermutability in DNA microsatellites (small repeated
sequences that occur throughout the genome).
Researchers studying MSI in CRC cell lines and primary tumors observed that 100%
of those analyzed contained deletions of 3 to 8 base pairs in the 17-thymine
nucleotide microsatellite (T17) located in Intron 8 of the gene encoding heat shock
protein 110 (HSP110). HSP110 can bind structurally similar heat shock proteins and
functions to facilitate proper protein folding and to reduce levels of nonfunctional
protein aggregates. The larger HSP110 T17 deletions cause Exon 9 to be omitted
from the final sequence during pre-mRNA processing. This generates a premature
stop codon in Exon 10, resulting in the mutant protein HSP110ΔE9. People with MSI
CRC have HSP110ΔE9 transcripts in cancerous tissue only.
Table 1 shows, with respect to T17-deletion size, the amount of HSP110ΔE9 mRNA
expressed relative to the total amount of HSP110 mRNA expressed in MSI CRC
primary tumor cells. The total amount of HSP110 mRNA expressed includes both
wild-type HSP110 (HSP110WT) and HSP110ΔE9 mRNA.
Page 1 of 69
,Question 2
1. Based on the data presented in the passage, which statement best describes the
HSP110ΔE9 allele?
A. Cancer-promoting and dominant to HSP110WT
B. Cancer-promoting and recessive to HSP110WT
C. Cancer-suppressing and dominant to HSP110WT
D. Cancer-suppressing and recessive to HSP110WT
Correct Answer
Answer:
C. Cancer-suppressing and dominant to HSP110WT
Reasoning:
A. Based on Figure 1, expression of HSP110ΔE9 results in reduced, not increased,
tumorigenicity. Thus, HSP110ΔE9 expression suppresses, it does not promote,
cancer.
B. Based on Figure 1, HSP110ΔE9 expression suppresses, it does not promote,
cancer. Furthermore, based on Table 2, HSP110ΔE9 expression is dominant, not
recessive, to HSP110 because it counteracts HSP110Δ activity in protein
aggregation.
C. Figure 1 shows that HSP110ΔE9 expressing cells have a reduced tumor
growth when injected in other mice. Based on Table 2, HSP110ΔE9 counteracts
the effects of HSP110 on protein aggregation and stimulates apoptosis, thus
HSP110ΔE9 expression is dominant to HSP110.
D. Based on Figure 1, HSP110ΔE9 expression is cancer-suppressing; however, the
effects of HSP110ΔE9 are dominant, and not recessive, to HSP110 because
HSP110ΔE9 is able to counteract the effects of HSP110 and stimulate apoptosis.
Page 2 of 69
,Question 3
2. Based on the passage, in MSI CRC primary tumor cells, the size of the deletion in
the HSP110 T17 microsatellite is inversely correlated with:
A. the amount of HSP110ΔE9 protein expressed.
B. the number of mature HSP110WT transcripts synthesized.
C. the frequency of the omission of HSP110 Exon 9 during splicing.
D. the extent of premature translation termination in Exon 10.
Correct Answer
Answer:
B. The number of mature HSP110WT transcripts synthesized
Reasoning:
A. The passage does not report protein levels for HSP110 or HSP110ΔE9.
B. Table 1 shows that as the number of deleted base pairs (bp) increases from
3 to 8, the levels of HSP110ΔE9 increase whereas the levels of HSP110
decrease. This data indicates that there is an inverse relationship between the
number of deleted bps and HSP110 levels.
C. The passage does not show a frequency of E9 omissions. It only indicates that the
larger omission results in deletion of E9.
D. The passage does not show the extent of premature translation termination, but
only the levels of HSP110ΔE9 and HSP110 transcripts (mRNA).
Page 3 of 69
, Question 4
A man with a CRC mutation that results in the synthesis of HSP110ΔE9 and a woman
that does not carry this mutation in any of her tissues have a child. What is the
percent chance that the child will inherit the CRC mutation?
A. 0%
B. 25%
C. 50%
D. 100%
Correct Answer
Answer:
A. 0%
Reasoning:
A. Based on the passage, HSP110ΔE9 is only expressed in somatic cells, not
germline. Thus, it cannot be inherited.
B. The passage indicates that HSP110ΔE9 is only expressed in cancerous cells;
therefore, it cannot be inherited.
C. As the transcripts are only expressed in cancerous cells, the mutation will not be
inherited.
D. The child is not likely to inherit the mutation because, based on the passage,
HSPΔE9 is only expressed in cancerous cells.
Page 4 of 69
