During translation, an mRNA molecule has a codon with the triplet sequence 5′-AUC-3′. Which anticodon sequence in a tRNA molecule would pair with this codon?
3′-UAG-5′
A ____ recognizes stop codons present at the A site of the ribosome to terminate elongation of a polypeptide chain.
release factor
When is a peptide bond formed during the process of translation?
During the elongation phase just after a tRNA charged with an amino acid binds to the A site on the ribosome
In which direction do incoming tRNA molecules move between the sites on the large ribosomal subunit as the elongation process takes place?
A-P-E
Which single-base substitution in the template strand of DNA would result in the premature termination of translation (sequences are written 5? to 3?)?
TTG to TTA
UAU and UAC both code for tyrosine. A change from UAU to UAC would thus be a _______ mutation; a change from UAU to UAG would be a _______ mutation.
silent; nonsense
Sickle-cell disease and hemoglobin C disease are both caused by point mutations, resulting in glutamic acid at position 6 in the ?-globin being replaced by _______ and _______, respectively.
valine; lysine
A protein destined for a lysosome carries a signal peptide for the
Rough ER
During protein synthesis, ribosomes
translate mRNA into polypeptides
Which component of transcribed RNA in eukaryotes is present in the primary transcript but is removed before translation occurs?
Intron
Posttranslational alterations of proteins
may include the addition of polysaccharides to proteins
In the elongation stage of translation,
rRNA is catalytically active
RNA polymerases differ from DNA polymerases in that
RNA polymerases are less effective at proofreading than DNA polymerases
Which component is not involved in the elongation step of translation?
RNA polymerase
Which component is required for the initiation of transcription?
Promoter DNA sequence
Why did the original “one-gene, one-enzyme” hypothesis have to be modified?
Some enzymes are made up of more than one polypeptide
In eukaryotes, the first amino acid in a growing polypeptide chain is always _____ because the codon for this amino acid is also the ____ codon.
methionine; start
Put the following four steps of eukaryotic gene expression in order, from beginning to end.
(1) Pre-mRNA is processed to make mRNA.
(2) Ribosomes translate the mRNA sequence to make proteins.
(3) mRNA is transported to the cytoplasm.
(4) DNA is used as a template to make pre-mRNA
4; 1; 3; 2
Ribosomes
carry out translation
At the initiation complex of translation in eukaryotes,
the anticodon of tRNA charged with methionine binds to mRNA associated with the small ribosomal subunit.
The mRNA codon for leucine is 5′-UUG-3′, and the tRNA anticodon is
5′-CAA-3′
Which statement about tRNAs is false?
They have an anticodon at their 5′ end and an amino acid attachment site at their 3′ end
Which statement about pre-mRNA splicing is false?
It is common in prokaryotes
What are the intracellular destinations of the following proteins: DNA polymerase; pyruvate kinase; rubisco; citrate synthase?
Nucleus; cytoplasm; chloroplast; mitochondrion
x

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