LIFESCI 7C — 100 Long Most Recent exam COMPLETE (2026)
EXAM Questions and Answers (Verified Answers) (Latest Update
2026) UPDATE!!
🔵 SECTION 1 — MOLECULAR BIOLOGY & GENE EXPRESSION (1–25)
1.
A researcher mutates a region 30 bp upstream of a gene’s transcription start site. After the
mutation, RNA polymerase II can still bind weakly, but transcription begins at multiple incorrect
locations, creating heterogeneous mRNA sizes.
Which specific promoter element was most likely disrupted?
The TATA box, which positions RNA polymerase II for accurate transcription
initiation.
2.
A mutation changes the DNA coding sequence from GAG to GAA. Lab tests show the protein
1
remains fully functional and the amino acid is unchanged.
Page
What type of mutation occurred and why is there no functional effect?
EXAMPREPMASTER
, Silent mutation; both codons encode glutamate, so the amino acid sequence is
unchanged.
3.
A scientist isolates the template strand of DNA containing the sequence 3’-GCTTACGGA-5’.
What is the correct mRNA transcript produced from this strand?
5’-CGA AUG CCU-3’
4.
A gene becomes transcriptionally silent when heavily methylated at CpG islands.
What is the direct consequence of DNA methylation enabling gene repression?
Recruitment of proteins that condense chromatin into heterochromatin, blocking
transcription factors.
5.
Mutating a splice donor site prevents removal of an intron.
What is the most likely consequence for translation?
A frameshift or premature stop codon due to inclusion of intronic sequence.
6.
A gene is activated only when a transcription factor binds to a promoter-proximal element.
Removing this factor leads to almost no transcription.
What regulatory mechanism does this illustrate?
Positive control requiring an activator.
7.
An enhancer located 20,000 bp from a gene increases its transcription.
How can it act at such a distance?
2
Page
EXAMPREPMASTER
, DNA looping brings the enhancer physically close to transcription machinery at the
promoter.
8.
You delete the AAUAAA signal from a eukaryotic gene.
What happens to the mRNA?
It fails to be cleaved and polyadenylated, resulting in instability and degradation.
9.
A transcription factor that binds DNA and blocks RNA polymerase binding reduces transcription
dramatically.
What is this protein acting as?
A repressor.
10.
A gene is transcribed normally, but translation fails to initiate because ribosomes cannot bind the
mRNA.
Which mRNA modification was most likely disrupted?
5’ cap addition.
11.
A scientist compares euchromatin and heterochromatin.
Which difference explains their opposite effects on transcription?
Euchromatin is loosely packed and accessible; heterochromatin is tightly condensed
and inaccessible.
12.
3
Page
EXAMPREPMASTER
EXAM Questions and Answers (Verified Answers) (Latest Update
2026) UPDATE!!
🔵 SECTION 1 — MOLECULAR BIOLOGY & GENE EXPRESSION (1–25)
1.
A researcher mutates a region 30 bp upstream of a gene’s transcription start site. After the
mutation, RNA polymerase II can still bind weakly, but transcription begins at multiple incorrect
locations, creating heterogeneous mRNA sizes.
Which specific promoter element was most likely disrupted?
The TATA box, which positions RNA polymerase II for accurate transcription
initiation.
2.
A mutation changes the DNA coding sequence from GAG to GAA. Lab tests show the protein
1
remains fully functional and the amino acid is unchanged.
Page
What type of mutation occurred and why is there no functional effect?
EXAMPREPMASTER
, Silent mutation; both codons encode glutamate, so the amino acid sequence is
unchanged.
3.
A scientist isolates the template strand of DNA containing the sequence 3’-GCTTACGGA-5’.
What is the correct mRNA transcript produced from this strand?
5’-CGA AUG CCU-3’
4.
A gene becomes transcriptionally silent when heavily methylated at CpG islands.
What is the direct consequence of DNA methylation enabling gene repression?
Recruitment of proteins that condense chromatin into heterochromatin, blocking
transcription factors.
5.
Mutating a splice donor site prevents removal of an intron.
What is the most likely consequence for translation?
A frameshift or premature stop codon due to inclusion of intronic sequence.
6.
A gene is activated only when a transcription factor binds to a promoter-proximal element.
Removing this factor leads to almost no transcription.
What regulatory mechanism does this illustrate?
Positive control requiring an activator.
7.
An enhancer located 20,000 bp from a gene increases its transcription.
How can it act at such a distance?
2
Page
EXAMPREPMASTER
, DNA looping brings the enhancer physically close to transcription machinery at the
promoter.
8.
You delete the AAUAAA signal from a eukaryotic gene.
What happens to the mRNA?
It fails to be cleaved and polyadenylated, resulting in instability and degradation.
9.
A transcription factor that binds DNA and blocks RNA polymerase binding reduces transcription
dramatically.
What is this protein acting as?
A repressor.
10.
A gene is transcribed normally, but translation fails to initiate because ribosomes cannot bind the
mRNA.
Which mRNA modification was most likely disrupted?
5’ cap addition.
11.
A scientist compares euchromatin and heterochromatin.
Which difference explains their opposite effects on transcription?
Euchromatin is loosely packed and accessible; heterochromatin is tightly condensed
and inaccessible.
12.
3
Page
EXAMPREPMASTER
