Chapter 14 MC Part 1

What is a ribozyme?

an RNA with enzymatic activity

Accuracy in the translation of mRNA into the primary structure of a polypeptide depends on specificity in the

bonding of the anticodon to the codon and the attachment of amino acids to tRNAs.

Alternative RNA splicing

can allow the production of proteins of different sizes and functions from a single mRNA.

A eukaryotic transcription unit that is 8,000 nucleotides long may use 1,200 nucleotides to make a protein consisting of approximately 400 amino acids. This is best explained by the fact that

many noncoding stretches of nucleotides are present in eukaryotic DNA.

There are 61 mRNA codons that specify an amino acid, but only 45 tRNAs. This is best explained by the fact that

the rules for base pairing between the third base of a codon and tRNA are flexible.

Which of the following is the first event to take place in translation in eukaryotes?

the small subunit of the ribosome recognizes and attaches to the 5' cap of mRNA

Which of the following does not occur in prokaryotic gene expression, but does occur in eukaryotic gene expression?

A poly-A tail is added to the 3' end of an mRNA and a cap is added to the 5' end.

Which of the following provides some evidence that RNA probably evolved before DNA?

DNA polymerase uses primer, usually made of RNA.

Which of the following best describes the significance of the TATA box in eukaryotic promoters?

It is the recognition site for a specific transcription factor.

RNA polymerase in a prokaryote is composed of several subunits. Most of these subunits are the same for the transcription of any gene, but one, known as sigma, varies considerably. Which of the following is the most probable advantage for the organism of such variability in RNA polymerase?

It might allow the polymerase to recognize different promoters under certain environmental conditions.

Which of the following statements best describes the termination of transcription in prokaryotes?

RNA polymerase transcribes through the terminator sequence, causing the polymerase to separate from the DNA and release the transcript.

In an experimental situation, a student researcher inserts an mRNA molecule into a eukaryotic cell after he has removed its 5' cap and poly-A tail. Which of the following would you expect him to find?

The molecule is digested by exonucleases because it is no longer protected at the 5' end.