DNA Structure
If there is 10% Adenine in a strand of DNA, what percent is Guanine?
40%
What part of a prokaryotic operon does a repressor bind to?
a. Promoter
b. Operator
c. Enhancer
d. Exon
Answer:B
Explanation: In prokaryotes, repressors bind to the operator to block transcription.
Which enzyme synthesizes short RNA primers?
a. DNA polymerase
b. Ligase
c. Primase
d. Helicase
Answer: c
Explanation: Primase lays down RNA primers to initiate DNA synthesis.
What is produced during transcription?
a. mRNA
b. DNA
c. Protein
d. tRNA
Answer: a
Explanation: Transcription synthesizes mRNA from a DNA template
Where does translation occur?
a. Nucleus
b. Ribosome
c. Mitochondria
d. Golgi
Answer: b
Explanation: Translation takes place at ribosomes in the cytoplasm
Which technique is used to amplify DNA segments in vitro?
a. CRISPR
b. Gel electrophoresis
c. PCR
d. Southern blot
C, PCR (Polymerase Chain Reaction) amplifies specific DNA segments
Which mechanism is an example of post-transcriptional regulation in eukaryotes?
a. Enhancer binding
b. DNA methylation
c. Alternative splicing
d. Transcription factors
C
What enzyme unzips the DNA helix during replication?
a. Ligase
b. Helicase
c. Polymerase
d. Primase
Answer: b
Explanation: Helicase unwinds and separates the DNA strands at the replication fork.
Where does transcription occur in eukaryotes?
a. Cytoplasm
b. Nucleus
c. Ribosome
d. Golgi body
Answer: b
Explanation: Transcription occurs in the nucleus and translation occurs in the cytoplasm of eukaryotic cells.
What is the function of tRNA?
a. Transcribes RNA
b. Carries amino acids
c. Replicates DNA
d. Codes for mRNA
Answer: b
Explanation: tRNA carries specific amino acids to the ribosome.
Explain how restriction enzymes and gel electrophoresis can be used in DNA fingerprinting.
a. They sequence DNA
b. They cut and separate DNA fragments
c. They amplify DNA
d. They denature proteins
B - They cut and separate DNA fragments
How does the lac operon function in the presence of lactose?
a. Repressor stays bound
b. Repressor is removed
c. Lactose prevents translation
d. RNA polymerase is blocked
B
Why is replication described as semi-conservative?
a. Each new helix is all new
b. Both strands are degraded
c. Only one strand is copied
d. One old and one new strand form each helix
Answer: d
Explanation: Each new DNA molecule contains one original and one new strand.
How does RNA polymerase know where to start transcription?
a. It reads introns
b. Binds to start codon
c. Binds to promoter
d. Follows ribosomes
Answer:C
Explanation: RNA polymerase binds to a promoter sequence to begin transcription.
What is the role of the start codon AUG?
a. Terminates translation
b. Binds the stop tRNA
c. Begins translation with methionine
d. Transcribes mRNA
Answer: c
Explanation: AUG signals the start of translation and codes for methionine.
Evaluate the ethical implications of genetic engineering in agriculture.
a. Always positive
b. No effect
c. Includes concerns about safety and biodiversity
d. Only benefits corporations
Answer:C
Explanation: There are both benefits and ethical concerns including biodiversity and safety.
Explain the role of transcription factors in gene expression.
a. They degrade mRNA
b. Initiate DNA replication
c. Translate proteins
d. Help RNA polymerase bind to DNA
Answer: d
Explanation: Transcription factors assist RNA polymerase in initiating transcription.
Evaluate the consequences of a mutation that disables DNA ligase.
a. Primers will not bind
b. Replication will begin early
c. Lagging strand fragments remain unconnected
d. No new bases will be added
Answer: c
Explanation: Ligase connects Okazaki fragments on the lagging strand.
Analyze the impact of a mutation in the promoter region.
a. Protein production increases
b. DNA cannot replicate
c. RNA polymerase becomes inactive
d. Transcription may not initiate
Answer:D
Explanation: Mutations in promoters can prevent RNA polymerase from binding and initiating transcription.
Analyze the effect of a frameshift mutation in translation.
a. Alters every downstream amino acid
b. Silent mutation
c. No change
d. Deletes a chromosome
Answer: A
Explanation: Frameshifts change all downstream codons, often leading to dysfunctional proteins.
How does DNA's antiparallel structure affect replication?
a. It speeds up synthesis
b. Causes errors
c. Requires different mechanisms for each strand
d. Prevents proofreading
Answer:C
Explanation: Each strand is synthesized differently because DNA strands run in opposite directions.
Compare the impact of DNA methylation versus histone acetylation on gene expression.
a. Both increase expression
b. Methylation decreases, acetylation increases
c. Both decrease expression
d. Both remove promoters
Answer:B
Explanation: Methylation usually silences genes while acetylation opens chromatin for transcription.
Explain the role of the leading and lagging strands in replication.
a. Both synthesize toward the fork
b. Leading is continuous, lagging is fragmented
c. Lagging strand is faster
d. Both go 3' to 5'
Answer: b
Explanation: The leading strand is synthesized continuously while the lagging strand is done in Okazaki fragments.
Explain how introns and exons are processed in eukaryotic transcription.
a. Introns are translated
b. Exons are removed
c. Introns are spliced out
d. Exons are destroyed
Answer: c
Explanation: Introns are removed during RNA processing and exons are spliced together.
Explain how codons and anticodons interact to build proteins.
a. Anticodons match mRNA codons to insert correct amino acids
b. Codons bind DNA
c. Codons digest mRNA
d. Anticodons are in DNA
Answer:A
Explanation: tRNA anticodons match codons on mRNA to ensure the correct amino acid is added.