Chapter 17:
In bacteria, transcription ends at a distinct site in each gene. What best describes transcription in eukaryotes?
Transcription ends at variable distances from the Poly (A) signal.
If a mutation rendered the sigma protein nonfunctional, what would result?
Transcription of bacterial genes would be reduced or eliminated.
In bacteria, when does transcription end?
When a stem-loop structure forms in the transcribed RNA
An advantage of introns is that they __________.
allow expression of different exon combinations from one gene
The release factor (RF) __________.
binds to the stop codon in the A site in place of a tRNA
A gene is a __________.
coding and regulatory sequence that directs the production of one or more related polypeptides or RNAs
The poly(A) tail at the end of eukaryotic mRNA __________.
helps protect the mRNA from degradation by enzymes in the cytoplasm; at the 3' end
The process of translation, whether in bacteria or eukaryotes, requires tRNAs, amino acids, ribosomal subunits, and __________.
initiation and elongation factors, plus GTP
A primary transcript in the nucleus of a eukaryotic cell is __________ the functional mRNA, whereas a primary transcript in a bacterial cell is __________ the functional mRNA.
larger than; the same size as
What molecule carries a genetic message from DNA to the protein-synthesizing components of the cell?
mRNA
According to the wobble hypothesis,....
more than one codon codes for an amino acid, and codons for the same amino acid tend to have the same nucleotides in the first two positions
During RNA splicing, which molecular component of the spliceosome catalyzes the excision reaction?
snRNA
What happens to introns in eukaryotic mRNA?
snRNPs bind to the primary transcript and form the spliceosome, which removes introns.
Ribosomes translate mRNAs into proteins with the help of ____________.
tRNAs
RNA polymerase reads the template strand. The non-template strand is ________.
the coding strand—its sequence matches the sequence of the RNA that is transcribed from the template strand
Amino acids are transferred from tRNAs...
to proteins
In what direction is RNA synthesized during transcription?
5′ to 3′
What best describes the spliceosome?
A complex molecular machine that splices introns out of pre-mRNA
What is true about translational initiation in bacteria?
A specific sequence on the small ribosomal subunit binds a complementary sequence on the mRNA.
Where does an amino acid attach to a tRNA?
At the 3′ end
What is true about transcription in bacteria and eukaryotes?
Bacteria and eukaryotes rely on proteins that recognize specific DNA sequences in the promoter to initiate transcription.
What about transcription in bacteria and eukaryotes is true?
Bacteria use only one RNA polymerase to transcribe RNA, whereas eukaryotes use three.
How does RNA polymerase begin transcription in eukaryotes?
By binding to promoter sequences in DNA
In bacteria, sigma binds to the polymerase before transcription begins. Bacterial RNA polymerase and sigma form what?
Holoenzyme
What best describes why eukaryotic transcription is more complex?
In eukaryotic transcription, the promoters are more diverse, and the primary RNA transcript must be extensively processed.
What best describes the significance of the TATA box in eukaryotic promoters?
It is the binding site for a transcription factor.
In a eukaryotic cell, what is true about post-translational modification of proteins?
Many proteins are modified chemically after they are synthesized
In a eukaryotic cell, what about post-translational modification of proteins is true?
Many proteins are modified chemically after they are synthesized.
What is the term for a complex of mRNA bound with multiple ribosomes, each synthesizing its own polypeptide strand?
Polyribosome
What transcribes protein-coding genes in eukaryotes?
RNA polymerase II
In eukaryotes, transcription normally stops when...
RNA polymerase reaches a termination signal on the DNA that leads to the formation of a hairpin loop in the mRNA
What best describes the termination of transcription in bacteria?
RNA polymerase transcribes a terminator sequence, causing the polymerase to separate from the DNA and release the transcript.
In transcription, ___________ produces an RNA molecule with a base sequence complementary to the base sequence of the _____________.
RNA polymerase; DNA template strand
Modifications needed for converting a primary transcript into a mature RNA are called...
RNA processing
What are the steps for terminating translation?
Release factor binds to stop codon; polypeptide and uncharged tRNAs are released; ribosome subunits separate
During elongation, what substrates are used for the polymerization reaction catalyzed by RNA polymerase?
Ribonucleoside triphosphates
In addition to RNA polymerase, transcription in eukaryotes requires...
Several transcription factors
What proteins associate with promoters in bacteria during transcription?
Sigma
The ____________ of the eukaryotic promoter is analogous to the __________ of the bacterial promoter.
TATA box; -10 box
What best describes the processing of eukaryotic pre-mRNAs in the proper order?
The addition of a 5′ cap; removal of introns; Poly (A) tail
What best describes the ribosome binding site?
The ribosome binding site is where the small ribosome subunit binds; it is located upstream of the start codon.
Which of the following statements best describes the ribosome binding site?
The ribosome binding site is where the small ribosome subunit binds; it is located upstream of the start codon.
What is true of the sequence called the TATA box?
The sequence is located 30 base pairs upstream of the transcription site and is important for recognition by RNA polymerase.
What factors are associated with transcription in eukaryotes?
Three polymerases, basal transcription factors, 5′ cap, and 3′ poly A tail
The lack of membrane-bound organelles in bacteria impacts transcription and translation in which way?
Transcription and translation can occur simultaneously
