Transcription and Translation
As a ribosome translocates along an mRNA molecule by one codon, which of the following occurs?
***NOT The tRNA that was in the A site moves into the P site and The tRNA that was in the P site moves to the E site and is released OR The tRNA that was in the A site moves into the P site OR The tRNA that was in the P site moves to the E site and is released.
If proteins were composed of only 12 different kinds of amino acids, what would be the smallest possible codon size in a genetic system with four different nucleotides?
2
An extraterrestrial life form is discovered. It has a genetic code much like that of organisms on Earth except that there are five different DNA bases instead of four and the base sequences are translated as doublets instead of triplets. How many different amino acids could be accommodated by this genetic code?
25
A particular triplet of bases in the template strand of DNA is 5 - AGT - 3 . The corresponding codon for the mRNA transcribed is
5 - ACU - 3
A particular eukaryotic protein is 300 amino acids long. Which of the following could be the maximum number of nucleotides in the DNA that codes for the amino acids in this protein?
903
During translation, chain elongation continues until what happens?
A stop codon is encountered
Which of the following does not occur during the termination phase of translation?
A tRNA with the next amino acid enters the P site.
There are 61 mRNA codons that specify an amino acid, but only 45 tRNAs. This is best explained by the fact that
A&B only
All of the following are directly involved in translation except
DNA
What is the effect of a nonsense mutation in a gene?
It introduces a stop codon into the mRNA
A particular triplet of bases in the coding strand of DNA is AAA The anticodon on the tRNA that binds the mRNA codon is
UUU
Which point mutation would be most likely to have a catastrophic effect on the functioning of a protein?
a base deletion near the start of a gene
Which of the following DNA mutations is the most likely to be damaging to the protein it specifies?
a base-pair deletion
During RNA processing a(n) ________ is added to the 3' end of the RNA.
a long string of adenine nucleotides
What enzyme catalyzes the attachment of an amino acid to tRNA?
aminoacyl-tRNA synthetase
Which of the following is the first event in translation in eukaryotes?
base pairing of activated methionine-tRNA to AUG of the messenger RNA
Accuracy in the translation of mRNA into the primary structure of a protein depends on specificity in the
binding of ribosomes to mRNA and bonding of the anticodon to the codon.
What are ribosomes composed of?
both rNA and protein
The anticodon of a particular tRNA molecule is
complementary to the corresponding mRNA codon.
A frameshift mutation could result from
either an insertion or a deletion of a base.
What are the coding segments of a stretch of eukaryotic DNA called?
exons
Which of the following are transcribed from DNA?
exons and mRNA
What are polyribosomes?
groups of ribosomes reading a single mRNA simultaneously
The function of the ribosome in polypeptide synthesis is to
hold mRNA and tRNAs together. catalyze the addition of amino acids from tRNAs to the growing polypeptide chain. move along the mRNA and eject tRNAs during the translocation process.
What type of bonding is responsible for maintaining the shape of the tRNA molecule?
hydrogen bonding between base pairs
All of the following are found in prokaryotic mRNA except
introns
Which of the following is not directly involved in the process of translation?
ligase
A codon
may code for the same amino acid as another codon.
Which of the following represents a similarity between RNA and DNA?
nucleotides consisting of a phosphate, sugar, and nitrogenous base
Of the following types of mutations, which one is likely to be the most common?
point mutation
Which of the following helps to stabilize mRNA by inhibiting its degradation?
poly-A-tail
What is the most abundant type of RNA?
rRNA
Which of the following is not a part of the eukaryotic transcription initiation complex?
snRNP
When does translation begin in prokaryotic cells?
soon after a transcription elongation begins
What is an anticodon part of?
tRNA
Base-pair substitutions involving the third base of a codon are unlikely to result in an error in the polypeptide. This is because
the base-pairing rules are less strict for the third base of codons and anticodons.
Translation occurs in
the cytoplasm.
Introns are significant to biological evolution because
their presence allows exons to be moved around more easily, creating proteins with new combinations of functional domains.
Which of the following is least related to the other items?
translation
