Bio Ch 17 questions
After transcription begins, several steps must be completed before the fully processed mRNA is ready to be used as a template for protein synthesis on the ribosomes. Which three statements correctly describe the processing that takes place before a mature mRNA exits the nucleus? -Noncoding sequences called introns are spliced out by molecular complexes called spliceosomes. -Coding sequences called exons are spliced out by ribosomes. -A poly-A tail (50-250 adenine nucleotides) is added to the 3' end of the pre-mRNA. -A translation stop codon is added at the 3' end of the pre-mRNA. -A cap consisting of a modified guanine nucleotide is added to the 5' end of the pre-mRNA.
-Noncoding sequences called introns are spliced out by molecular complexes called spliceosomes. -A poly-A tail (50-250 adenine nucleotides) is added to the 3' end of the pre-mRNA. -A cap consisting of a modified guanine nucleotide is added to the 5' end of the pre-mRNA.
Place the events in the transcription of a gene in their proper order from left (first event) to right (last event). Rank from first event to last event.
1) RNA polymerase binds promoter 2) RNA polymerase transcribes gene 3) RNA polymerase reaches terminator 4) RNA polymerase exit gene. RNA is released
The direction of synthesis of an RNA transcript is _____. 1' —> 5' 5' —> 3' 1' —> 3' 3' —> 5' 2' —> 4'
5' ---> 3'
Why is a frameshift missense mutation more likely to have a severe effect on phenotype than a nucleotide-pair substitution missense mutation in the same protein? -A frameshift missense mutation will cause an early Stop codon, but a substitution missense might be silent. -A frameshift missense will cause the codons to be out of order, but a substitution missense does not change the order of the codons. -A substitution missense mutation causes the protein to be shorter and thus non-functional. -A substitution missense affects only one codon, but a frameshift missense affects all codons downstream of the frameshift.
A substitution missense affects only one codon, but a frameshift missense affects all codons downstream of the frameshift.
At which site do new aminoacyl tRNAs enter the ribosome during elongation? -A-site -E-site -B-site -P-site
A-site
How is translation initiated? -The small ribosomal subunit binds to the mRNA. -The tRNA bearing methionine binds to the start codon. -The large ribosomal subunit binds to the small one. -The start codon signals the start of translation. -All of the above.
All of the above
Which of the following molecules is/are produced by translation? Include molecules that are subject to further modification after initial synthesis. Select all that apply. -The amino acid glycine -Aminoacyl-tRNA synthetase -RNA polymerase
Aminoacyl-tRNA synthetase, RNA polymerase
What determines which base is to be added to an RNA strand during transcription? -Base pairing between the two DNA strands -The previous base -The order of the chemical groups in the backbone of the RNA molecule -Base pairing between the DNA template strand and the RNA nucleotides
Base pairing between the DNA template strand and the RNA nucleotides
The tRNA anticodon, GAC, is complementary to the mRNA codon with the sequence _____. -CAG -CTG -GAC -CUG -TCG
CUG
Which component is not directly involved in translation? -ribosomes -mRNA -tRNA -GTP -DNA
DNA
Which of the following is not true of RNA processing? -Exons are cut out before mRNA leaves the nucleus. -A primary transcript is often much longer than the final RNA molecule that leaves the nucleus. -Ribozymes may function in RNA splicing. -Nucleotides may be added at both ends of the RNA. -RNA splicing can be catalyzed by spliceosomes.
Exons are cut out before mRNA leaves the nucleus.
True or false. A tRNA with an anticodon complementary to the stop codon catalyzes the reaction by which translation is terminated.
False
Think about the DNA coding sequence of a gene. If an A were swapped for a T, what kind of mutation could it cause and why? -It could cause a frameshift nonsense or frameshift missense mutation because it would change the reading frame of the codon triplet. -It could cause a nonsense mutation because the sequence would no longer be the same, so the protein would be shorter and non-functional. -It could cause a silent mutation because A and T are complementary to each other so it is not really a substitution mutation. -It could cause a silent, missense, or nonsense mutation because those are the types that can be caused by a nucleotide-pair substitution like this one.
It could cause a silent, missense, or nonsense mutation because those are the types that can be caused by a nucleotide-pair substitution like this one.
Which of the following is not true of a codon? -It extends from one end of a tRNA molecule. -It consists of three nucleotides. -It is the basic unit of the genetic code. -It never codes for more than one amino acid. -It may code for the same amino acid as another codon.
It extends from one end of a tRNA molecule.
What happens to RNA polymerase II after it has completed transcription of a gene? -It is free to bind to another promoter and begin transcription. -It is degraded. -It joins with another RNA polymerase to carry out transcription. -It begins transcribing the next gene on the chromosome.
It is free to bind to another promoter and begin transcription.
Where does RNA polymerase begin transcribing a gene into mRNA? -The ribosome directs it to the correct portion of the DNA molecule. -Transfer RNA acts to translate the message to RNA polymerase. -It looks for the AUG start codon. -It starts after a certain nucleotide sequence called a promoter.
It starts after a certain nucleotide sequence called a promoter.
The initiator tRNA attaches at the ribosome's _____ site. -A -translocation -E -P -Q
P
Which of the following processes is an example of a post-translational modification? -Initiation -Peptide bond formation -Phosphorylation -Elongation
Phosphorylation
What name is given to the process in which pre-mRNA is edited into mRNA? -RNA processing -gene expression -polypeptide formation -transcription -translation
RNA processing
Which of the following steps occurs last in the initiation phase of translation? -An aminoacyl tRNA binds to the start codon. -A peptide bond is formed between two adjacent amino acids. -The small subunit of the ribosome binds to the 5' cap on the mRNA. -The large ribosomal subunit joins the complex.
The large ribosomal subunit joins the complex.
Which of the following statements best describes the promoter of a protein-coding gene? -The promoter is a site at which only RNA polymerase will bind. -The promoter is part of the RNA molecule itself. -The promoter is a site found on RNA polymerase. -The promoter is a nontranscribed region of a gene.
The promoter is a nontranscribed region of a gene.
What is meant by translocation? -The ribosome slides one codon down the mRNA. -The completed polypeptide is released from the ribosome. -The two ribosomal subunits are joined in a complex. -The polypeptide chain grows by one amino acid.
The ribosome slides one codon down the mRNA.
What is a ribozyme? -a mutated ribosome -a biological catalyst made of RNA -a biological catalyst consisting of DNA -an enzyme that holds open the DNA double helix while RNA polymerase adds nucleotides -a DNA sequence near the promoter that assists in the binding of RNA polymerase
a biological catalyst made of RNA
What does a mutagen cause? -problems with mitosis -decreased enzyme activity throughout the cell -decreased permeability of the nuclear envelope -a reduction in the number of tRNA molecules available for protein synthesis -a change in the sequence of DNA
a change in the sequence of DNA
Transcription begins at a promoter. What is a promoter? -A site found on the RNA polymerase -A site in DNA that recruits the RNA Polymerase -Part of the RNA molecule itself -The same as a start codon
a site in DNA that recruits the RNA polymerase
Polypeptides are assembled from _____. -hexoses -glycerol -nucleotides -proteins -amino acids
amino acids
Amino acids are attached to tRNA by enzymes called
aminoacyl-tRNA synthase
What enzyme catalyzes the attachment of an amino acid to tRNA? -aminoacyl-tRNA synthetase -rubisco -dextrinase -argininosuccinate lyase -nuclease
aminoacyl-tRNA synthetase
Which of the following terms best describes the relationship between the newly synthesized RNA molecule and the DNA template strand? -Permanently base-paired -Complementary -Identical -Covalently bound
complementary
The anticodon of a particular tRNA molecule is -complementary to the corresponding triplet in rRNA. -complementary to the corresponding mRNA codon. -changeable, depending on the amino acid that attaches to the tRNA. -catalytic, making the tRNA a ribozyme. -the part of tRNA that bonds to a specific amino acid.
complementary to the corresponding mRNA codon.
Translation occurs in the _____. -cytoplasm -lysosome -nucleus -Golgi apparatus -nucleoplasm
cytoplasm
The RNA segments joined to one another by spliceosomes are _____. -caps -exons -snRNPs -tails -introns
exons
The flow of information in a cell proceeds in what sequence? -from RNA to DNA to protein -from DNA to RNA to protein -from DNA to protein to RNA -from protein to RNA to DNA -from RNA to protein to DNA
from DNA to RNA to protein
After an RNA molecule is transcribed from a eukaryotic gene, what are removed and what are spliced together to produce an mRNA molecule with a continuous coding sequence? -operators ... promoters -exons ... introns -promoters ... operators -silencers ... enhancers -introns ... exons
introns...exons
RNA processing converts the RNA transcript into _____. -a protein -DNA -a eukaryotic cell -mRNA -a polypeptide
mRNA
Which nucleic acid is translated to make a protein? -rRNA -tRNA -DNA -mRNA
mRNA
A _____ mutation causes a wild-type amino acid to be replaced by a different amino acid.
missense
A _______ mutation causes an early Stop codon to occur.
nonsense
The RNA that has an amino acid attached to it, and that binds to the codon on the mRNA, is called a
tRNA
A codon consists of _____ bases and specifies which _____ will be inserted into the polypeptide chain. -four ... fatty acid -four ... amino acid -three ... nucleotide -two ... nucleotide -three ... amino acid
three...amino acid
What is the process called that converts the genetic information stored in DNA to an RNA copy? -Translocation -Translation -Transcription -Replication
transcription
What name is given to the process in which a strand of DNA is used as a template for the manufacture of a strand of pre-mRNA? -RNA processing -gene expression -polypeptide formation -transcription -translation
transcription
The process, performed by the ribosome, of reading mRNA and synthesizing a protein is called
translation
What name is given to the process in which the information encoded in a strand of mRNA is used to construct a protein? -RNA processing -gene expression -polypeptide formation -transcription -translation
translation
Which of the following sequences shows a frameshift mutation compared to the wild-type mRNA sequence? wild-type 5'-AUGCAUACAUUGGAGUGA-3' mutant 5'-AUGCAUACAUCUGGAGUGA-3' wild-type 5'-AUGCAUACAUUGGAGUGA-3' mutant 5'-AUGCAUGUGACAUUGGAGUGA-3' wild-type 5'-AUGCAUACAUUGGAGUGA-3' mutant 5'-AUGCAUACAGAGUGA-3' wild-type 5'-AUGCAUACAUUGGAGUGA-3' mutant 5'-AUGCAUACGUUGGAGUGA-3'
wild-type 5'-AUGCAUACAUUGGAGUGA-3' mutant 5'-AUGCAUACAUCUGGAGUGA-3'
Which of these is currently considered the best definition of a gene? -A gene codes for a single enzyme. -A gene codes for either a polypeptide or an RNA molecule. -A gene codes for a particular ribozyme. -A gene codes for a single polypeptide. -A gene codes for a single protein.
A gene codes for either a polypeptide or an RNA molecule.
What is the function of RNA polymerase? -It adds nucleotides to the 5' end of the growing mRNA molecule. -It relies on other enzymes to unwind the double helix. -It proceeds slowly along the DNA strand, requiring about a minute to add two nucleotides to the growing mRNA molecule. -It unwinds the double helix and adds nucleotides to a growing strand of RNA. -All of the above.
It unwinds the double helix and adds nucleotides to a growing strand of RNA.
The average length of a transcription unit along a eukaryotic DNA molecule is about 27,000 nucleotide pairs, whereas an averaged-sized protein is about 400 amino acids long. What is the best explanation for this fact? -Each amino acid in a protein is encoded by a triplet of nucleotides. -Many genes are subject to alternative RNA splicing. -Most eukaryotic genes and their RNA transcripts have long noncoding stretches of nucleotides that are not translated.
Most eukaryotic genes and their RNA transcripts have long noncoding stretches of nucleotides that are not translated.
Suppose that the triplet of nucleotides indicated in bold (AGC) spans two codons, that is, CTA and GCC. If the triplet AGC were deleted from this DNA coding sequence, what effect would it have on the resulting protein? 5'-ATGCTAGCCTATCGTAAC-3' -The entire amino acid sequence would be altered due to the frameshift. -All of the amino acids after the deletion would be altered due to the frameshift. -The two flanking codons would be altered, but the rest of the amino acid sequence would be the same because there would be no frameshift. -All of the amino acids up to the deletion would be altered due to the frameshift.
The two flanking codons would be altered, but the rest of the amino acid sequence would be the same because there would be no frameshift.
During RNA processing a(n) _____ is added to the 3' end of the RNA. -3' untranslated region -a long string of adenine nucleotides -5' untranslated region -coding segment -modified guanine nucleotide
a long string of adenine nucleotides
Which of the following mutations would be most likely to have a harmful effect on an organism? -a single nucleotide deletion in the middle of an intron -a single nucleotide deletion near the end of the coding sequence -a deletion of three nucleotides near the middle of a gene -a nucleotide-pair substitution -a single nucleotide insertion downstream of, and close to, the start of the coding sequence
a single nucleotide insertion downstream of, and close to, the start of the coding sequence
of translation always happens at the start codon of the mRNA.
initiation
During RNA processing a(n) _____ is added to the 5' end of the RNA. -3' untranslated region -a long string of adenine nucleotides -5' untranslated region -coding segment -modified guanine nucleotide
modified guanine nucleotide
DNA does not store the information to synthesize which of the following? -Proteins -Organelles -Messenger RNA -DNA
organelles
Which of the following terms associated with transcription describe regions of nucleic acid? -promoter -RNA polymerase -gene -terminator
promoter gene terminator
Where does translation take place? -Ribosome -Golgi apparatus -Endoplasmic reticulum -Nucleus
ribosome
Which of the following molecules are produced by transcription? Select all that apply. -Ribosomal proteins -Messenger RNA -Ribozymes
ribozymes, messenger RNA
In eukaryotic cells, transcription cannot begin until -DNA nucleases have isolated the transcription unit. -several transcription factors have bound to the promoter. -the DNA introns are removed from the template. -the two DNA strands have completely separated and exposed the promoter. -the 5' caps are removed from the mRNA.
several transcription factors have bound to the promoter.
A ______ mutation does not change the wild-type amino acid sequence.
silent
Spliceosomes are composed of _____. -small RNAs and proteins -polymerases and ligases -introns and exons -the RNA transcript and protein
small RNAs and proteins
of translation happens when the ribosome hits a stop codon on the mRNA.
termination
During transcription in eukaryotes, a type of RNA polymerase called RNA polymerase II moves along the template strand of the DNA in the 3'→5' direction. However, for any given gene, either strand of the double-stranded DNA may function as the template strand. For any given gene, what ultimately determines which DNA strand serves as the template strand? -the location of specific proteins (transcription factors) that bind to the DNA -the base sequence of the gene's promoter -which of the two strands of DNA carries the RNA primer -the location along the chromosome where the double-stranded DNA unwinds
the base sequence of the gene's promoter
