Chapter 15 Review Questions

The AUC and AUA codons in mRNA both specify isoleucine. What feature of the genetic code explains this?

Degeneracy

How many nucleotides are in 12 mRNA codons?

36

What is often the first amino acid added to a polypeptide chain?

Methionine

Where are the RNA components of ribosomes synthesized?

Nucleolus

Which feature of promoters can be found in both prokaryotes and eukaryotes?

TATA box

The DNA of virus A is inserted into the protein coat of virus B. The combination virus is used to infect E. coli. The virus particles produced by the infection are analyzed for DNA and protein. What results would you expect?

DNA and protein from A

A poly-A sequence is added at the —

3′ end of a transcript in the nucleus

Peptide bond synthesis in prokaryotic translation is catalyzed by —

ribosomal RNA

The sequence that signals the end of transcription is called the —

terminator

In any given species, there are at least how many types of aminoacyl tRNA synthetases?

20

Which pre-mRNA processing step is important for initiating translation?

Adding the 7-methylguanosine cap

What processing step enhances the stability of pre-tRNAs and pre-rRNAs?

Methylation

What is the flow of information for protein synthesis according to the central dogma?

DNA to mRNA to protein

Which feature distinguishes eukaryotic transcription from bacterial transcription?

Eukaryotic transcription and translation do not take place at the same time.

At what stage in the transcription of a eukaryotic gene would TFII factors be active?

Initiation

If the ρ protein is missing, will a prokaryotic gene be terminated?

It depends on the gene.

Which option is associated with the docking of mRNA on a ribosome in eukaryotic cells?

Kozak's rules

Which polymerase is responsible for the synthesis of 5S rRNA?

Polymerase III

What transcripts will be most affected by low levels of α -amanitin?

Pre-mRNAs

Which molecule does NOT contain genetic information?

Protein

What would happen if the 5′-methyl guanosine was NOT added to an mRNA?

The transcript would be degraded when the mRNA moves out of the nucleus to the cytoplasm.

Why are the −10 and −35 regions of prokaryotic promoters called consensus sequences?

They are similar in all bacterial species.

What are introns?

Untranslated DNA sequences in a gene

In prokaryotic cells, ribosomes are found in/on the —

cytoplasm

Which molecule in the central dogma can be compared to a disposable photocopy of a book kept on reserve in the library?

mRNA

Which subunit of the E. coli polymerase confers specificity to transcription?

σ