15. Gene Expression

In eukaryotes, which mechanism operates after transcription, but before translation of mRNA into protein?

Which accurately describes the usual process of eukaryotic transcription?

Which statement correctly describes mRNA processing?

Two different proteins with mostly different structures are translated from two different mRNAs. These mRNAs, however, were transcribed from the same gene. Which mechanism could best account for this?

What is a key difference between eukaryotic and prokaryotic gene expression?

Splicing begins:a. as transcription occurs.b. after transcription is complete.c. as translation occurs.d. after translation is complete.

Compared with mRNAs that have a cap and tail, predict what will be observed if a eukaryotic mRNA lacked a cap and poly(A) tail.a. The primary transcript would not be processed properly.b. Translation would occur inefficiently.c. Enzymes on the ribosome would add a cap and poly(A) tail.d. tRNAs would become more resistant to degradation.

Which of the following is true of RNA processing? (A) Exons are cut out before mRNA leaves the nucleus. (B) Nucleotides are added at both ends of the RNA. (C) Ribozymes may function in the addition of a 5′ cap. (D) RNA splicing adds a poly-A tail to the mRNA.

Which of the following is not true of RNA processing?a. Exons are cut out before mRNA leaves the nucleus.b. Nucleotides may be added at both ends of the RNA.c. Ribozymes may function in RNA splicing.d. RNA splicing can be catalyzed by spliceosomes.

RNases and proteases are enzymes that destroy RNAs and proteins, respectively. Which of the following enzymes, if added to a spliceosome, would be predicted to prevent recognition of pre-mRNA regions critical for splicing?a. an RNase specific for tRNAsb. an RNase specific for snRNAsc. a protease specific for initiation factorsd. a protease specific for a release factor

Would the coupling of the processes shown in Figure 17.24 be found in a eukaryotic cell? Explain why or why not.

Biologists have investigated how fast pre-mRNA splicing occurs by treating cells with a toxin that blocks the production of new pre-mRNAs, then following the rate of splicing of the pre-mRNAs that were transcribed before adding the toxin. Why is addition of a toxin important in this study?