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WorksheetsCh. 15 review
Total questions: 78
Worksheet time: 39mins
Which term refers to the hypothesis that each gene encodes a single polypeptide?
One gene / one polypeptide hypothesis
Central Dogma
Transcription
Translation
What is the process called where DNA is converted into RNA?
Translation
Transcription
Replication
Mutation
Which molecule acts as the template for protein synthesis during translation?
mRNA
tRNA
rRNA
DNA
What is the role of Beadle and Tatum’s experiments with Neurospora crassa?
To show that genes specify enzymes
To prove DNA replication
To discover the structure of RNA
To identify codons
Which term describes a mutation that shifts the reading frame of the genetic message?
Point mutation
Frameshift mutation
Translocation
Intron
According to the central dogma of molecular biology, what is the usual flow of genetic information?
Protein → RNA → DNA
DNA → RNA → Protein
RNA → DNA → Protein
DNA → Protein → RNA
Which process involves changing nucleotide sequences into amino acid sequences?
Transcription
Translation
Replication
Mutation
What is the significance of Garrod’s conclusion regarding inherited disorders?
They can involve specific enzymes
They are always caused by environmental factors
They are unrelated to genes
They only affect physical traits
How did Beadle and Tatum link gene mutations to specific enzymes?
By supplementing with pathway intermediates
By sequencing DNA
By observing cell division
By measuring protein synthesis rates
What modification to the central dogma was made after the discovery of reverse transcriptase?
DNA can be made from RNA
Proteins can be made from DNA directly
RNA cannot be transcribed from DNA
Translation does not occur
Which enzyme is responsible for producing a copy of RNA from DNA during transcription?
RNA polymerase
DNA ligase
Helicase
Topoisomerase
During transcription, which strand of DNA is complementary to the RNA produced?
Template strand
Coding strand
Sense strand
Antisense strand
What is the main function of mRNA in gene expression?
Carries the code from DNA out of the nucleus to the ribosome
Synthesizes amino acids
Acts as a component of ribosomes
Pairs with mRNA and carries amino acids
Which type of RNA has an anticodon to pair with mRNA and carries amino acids used to build proteins?
tRNA
mRNA
rRNA
snRNA
What is the role of siRNA in gene expression?
Regulatory function
Carries the code from DNA
Component of ribosomes
Directs translation to RoughER
How many possible codon sequences are there with four base pairs?
64
16
32
128
What do the three stop codons (UAA, UAG, UGA) indicate in genetic coding?
Termination of translation
Start of transcription
Initiation of replication
Splicing of mRNA
Why do frameshift mutations alter the reading frame?
Because they involve the deletion or addition of a base
Because they change the base pairing rules
Because they only affect the template strand
Because they occur during translation
Explain how Crick and Brenner demonstrated the lack of spaces in genetic coding.
They induced mutations that deleted single, double, and triple nucleotides from DNA and observed the protein products.
They compared DNA sequences with and without spaces.
They used RNA polymerase to transcribe DNA with spaces.
They measured the length of mRNA transcripts.
Why is the genetic code described as degenerate but specific?
Because multiple codons can code for the same amino acid, but each codon specifies only one amino acid.
Because codons can code for multiple amino acids.
Because the code changes with mutations.
Because the code is not universal.
Which codon indicates the beginning of translation in protein synthesis?
UAA
AUG
UGA
GCU
How many of the 64 codons specify amino acids?
20
61
64
3
What is the wobble effect in the genetic code?
The effect of codon redundancy at the first position
The effect of degenerate base at the third nucleotide position
The effect of stop codons on translation
The effect of AUG codon on translation initiation
Why is the universality of the genetic code considered strong evidence for a common ancestor?
Because all organisms have identical genes
Because all organisms use the same codons for amino acids
Because the genetic code is nearly universal among organisms
Because all organisms have the same number of chromosomes
Which RNA polymerase feature is unique to prokaryotes?
Multiple types of RNA polymerase
A single RNA polymerase with multiple subunits
RNA polymerase with proofreading ability
RNA polymerase that synthesizes DNA
Where are prokaryotic promoter recognition sites typically located?
+10 and +35 downstream from the start site
-10 and -35 upstream from the start site
-20 and -50 upstream from the start site
+20 and +50 downstream from the start site
What is the role of the transcription unit in prokaryotic transcription?
It binds ribosomes to mRNA
It is the DNA from the promoter to the terminator sequence
It synthesizes proteins
It degrades mRNA
During elongation in prokaryotic transcription, which nucleotide does the 5’ end often begin with?
GTP
CTP
ATP
TTP
What is the most common mechanism for termination in prokaryotic transcription?
Formation of a hairpin structure
Cleavage by ribonuclease
Addition of poly-A tail
Binding of release factor
How is prokaryotic transcription coupled to translation?
Transcription and translation occur in separate compartments
Multiple ribosomes begin translation as soon as mRNA is available
Transcription occurs only after translation is complete
Only one ribosome can translate mRNA at a time
Why are operons significant in prokaryotic gene expression?
They allow multiple genes to be translated as one mRNA
They prevent transcription of unnecessary genes
They increase the accuracy of translation
They separate transcription and translation
Explain why genes can be transferred from one organism to another, according to the universality of the genetic code.
Because all organisms have the same DNA sequence
Because the genetic code is nearly universal, allowing gene expression across species
Because only prokaryotes share genetic material
Because all organisms have identical ribosomes
Compare the coupling of transcription and translation in prokaryotes and eukaryotes.
Both are coupled in prokaryotes and eukaryotes
Only eukaryotes couple transcription and translation
Prokaryotes couple transcription and translation, while eukaryotes do not
Neither prokaryotes nor eukaryotes couple transcription and translation
Describe the process of initiation at promoters in prokaryotic transcription.
RNA polymerase binds to the terminator sequence
RNA polymerase binds to a recognition site upstream of the start site, indicating attachment and direction of transcription
Ribosomes bind to the mRNA before transcription begins
DNA polymerase binds to the promoter region
Which RNA polymerase in eukaryotes is responsible for transcribing mRNA and snRNA?
RNA polymerase I
RNA polymerase II
RNA polymerase III
RNA polymerase IV
What is the function of the 5’ Methyl G cap added to eukaryotic mRNA transcripts?
Initiates transcription
Protects the end from degradation and allows binding to the ribosome
Splices introns from mRNA
Terminates transcription
Which sequence in eukaryotic promoters is comparable to the -10 sequence in prokaryotes?
Poly A tail
TATA sequence
Shine-Dalgarno sequence
Pribnow box
What is the role of polyadenylation in eukaryotic transcription?
Initiates transcription
Adds a 3’ poly A tail to mRNA, protecting it from degradation and regulating transcript products
Splices exons together
Binds transcription factors to the promoter
Which process allows a single primary transcript to be spliced into different mRNAs using different sets of exons?
Polyadenylation
Alternative splicing
Translation
Replication
What is the function of the spliceosome in eukaryotic cells?
Adds a 5’ cap to mRNA
Recognizes intron-exon junctions and removes introns from mRNA
Initiates transcription
Terminates translation
Approximately what percentage of the human genome is made up of exons?
24%
50%
1-1.5%
80%
How many genes does the human genome have, and how many proteins can it produce?
20,000 genes, can produce more than 80,000 proteins
80,000 genes, can produce 20,000 proteins
24,000 genes, can produce 24,000 proteins
1,000 genes, can produce 10,000 proteins
Why can the human genome produce more proteins than the number of genes it contains?
Because of alternative splicing
Because of DNA replication
Because of translation errors
Because of RNA polymerase I activity
Which of the following best describes the transcriptome?
All the proteins produced from the genome
All the RNAs produced from the genome
All the DNA sequences in the genome
All the exons in the genome
Which molecule is responsible for attaching amino acids to tRNA with the correct anticodon?
Aminoacyl-tRNA synthetase
Ribosome
mRNA polymerase
DNA ligase
What is the shape of tRNA?
Double helix
Cloverleaf
Linear
Circular
Which part of tRNA base-pairs with mRNA codons?
Acceptor end
Anticodon loop
D loop
Variable arm
What happens to tRNA once it has bound an amino acid?
It is degraded
It is “charged”
It is exported from the nucleus
It binds to DNA
Which ribosomal site accepts new charged tRNAs with anticodons complementary to mRNA?
P site
E site
A site
S site
What is the function of the P site in the ribosome?
Releases empty tRNA
Binds new charged tRNA
Catalyzes peptide bond formation
Decodes mRNA
Which ribosomal subunit is responsible for binding mRNA and decoding it?
Large subunit
Small subunit
Both subunits
tRNA
During prokaryotic initiation, which amino acid is first attached to the initiator tRNA?
Methionine
N-formylmethionine
Glycine
Alanine
In eukaryotic initiation, what does the small ribosomal subunit bind to?
3’ end of mRNA
5’ cap of mRNA
tRNA anticodon
DNA promoter
Why does the ribosome use the first AUG in an mRNA?
To signal the end of translation
To encode the amino acid glycine
To signal the start of translation
To attach the ribosome to DNA
Which ribosomal site is where empty tRNA is released from the ribosome?
A site
P site
E site
S site
What is the main enzymatic function of the large ribosomal subunit?
Decoding mRNA
Formation of peptide bonds between amino acids
Binding tRNA
Synthesizing DNA
Explain the difference between prokaryotic and eukaryotic initiation in translation.
Prokaryotes use more initiation factors than eukaryotes
Eukaryotes use N-formylmethionine as the first amino acid
Prokaryotes bind the small subunit to a conserved mRNA sequence, while eukaryotes bind to the 5’ cap of mRNA
Both use the same process
What is the role of accessory factors in translation initiation?
They degrade mRNA
They help the ribosome recognize the start codon and assemble properly
They synthesize amino acids
They transport tRNA out of the nucleus
Which enzyme attaches an amino acid to the acceptor end of tRNA?
DNA polymerase
Aminoacyl-tRNA synthetase
RNA helicase
Peptidyl transferase
Which site does the next tRNA with an anticodon that pairs to the codon enter during elongation in translation?
A site
P site
E site
G site
What is the function of release factors during termination of translation?
They bind the stop codon and release the polypeptide.
They add amino acids to the growing chain.
They pair with tRNA anticodons.
They initiate transcription.
In eukaryotes, translation can occur in which cellular locations?
Cytoplasm or roughER
Nucleus or mitochondria
Golgi apparatus or lysosome
Plasma membrane or peroxisome
What is the role of the signal recognition particle (SRP) in protein targeting?
It binds the new polypeptide and receptor on the roughER, directing translation into roughER.
It synthesizes amino acids.
It degrades mRNA.
It transports ribosomes to the nucleus.
Which process describes the conversion from genotype to phenotype?
Gene expression
Mutation
Replication
Translocation
What is a point mutation?
A change that alters a single base in DNA
A deletion of an entire gene
A duplication of a chromosome
A fusion of two genes
Which type of mutation changes a codon to a stop codon?
Nonsense mutation
Missense mutation
Silent mutation
Frameshift mutation
What is an indel?
A small insertion or deletion in DNA
A large chromosomal rearrangement
A point mutation
A change in gene expression
How do frameshift mutations affect the reading frame?
They shift the reading frame and randomize the downstream sequence.
They only change one amino acid.
They duplicate the entire gene.
They have no effect on the protein.
What is copy number variation (CNV)?
A type of structural variation involving changes in the number of copies of a gene
A single base substitution
A silent mutation
A frameshift mutation
Which type of DNA mutation results in a portion of DNA being lost?
Deletion
Duplication
Inversion
Translocation
What is the effect of duplication in DNA mutations?
A portion of DNA is copied
A portion of DNA is lost
A portion of DNA is excised and inverted
A portion of DNA is moved to another chromosome
Balanced rearrangements in DNA do not change which of the following?
Copy number
DNA sequence
Mutation rate
Evolutionary starting point
Which DNA mutation involves a portion of DNA being excised, inverted, and inserted?
Inversion
Deletion
Duplication
Translocation
Translocation in DNA mutations refers to which process?
Portion moved from one chromosomal location to another
Portion of DNA is lost
Portion of DNA is copied
Portion of DNA is excised and inverted
Why are mutations considered important in the context of evolution?
They are the starting point of evolution
They prevent genetic variation
They always cause disease
They stop natural selection
Which statement is true regarding human mutation rates?
They have been directly measured
They cannot be measured
They are always constant
They are only estimated
Explain how balanced rearrangements differ from unbalanced rearrangements in terms of their effect on DNA copy number.
Balanced rearrangements do not change copy number, while unbalanced rearrangements do.
Both types increase copy number.
Both types decrease copy number.
Balanced rearrangements always delete DNA.
A scientist observes a mutation where a segment of DNA is moved from one chromosome to another. Which type of mutation is this, and what could be a possible consequence for the organism?
Translocation; it may disrupt gene function or regulation
Duplication; it always increases gene expression
Inversion; it never affects phenotype
Deletion; it always causes lethality
