Openstax biology 2e chapter 15

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

• complementarity

• nonsense codons

• universality

• degeneracy

How many nucleotides are in 12 mRNA codons?

• 12

• 24

• 36

• 48

Which event contradicts the central dogma of molecular biology?

• Poly-A polymerase enzymes process mRNA in the nucleus.

• Endonuclease enzymes splice out and repair damaged DNA.

• Scientists use reverse transcriptase enzymes to make DNA from RNA.

• Codons specifying amino acids are degenerate and universal.

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

• GC box

• TATA box

• octamer box

• -10 and -35 sequences

How do enhancers and promoters differ?Promoters bind transcription factors to increase the efficiency of transcription.

• Enhancers bind transcription factors to silence gene expression, while promoters activate transcription.

• Enhancers increase the efficiency of gene expression, but are not essential for transcription. Promoter recognition is essential to transcription initiation.

• Enhancers bind RNA polymerases to initiate transcription. There is no difference.

• Both are transcription factor-binding sequences in DNA.

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

• poly-A tail

• RNA editing

• splicing

• 7-methylguanosine cap

The RNA components of ribosomes are synthesized in the ________.

• cytoplasm

• nucleus

• nucleolus

• endoplasmic reticulum

A scientist introduces a mutation that makes the 60S ribosomal subunit nonfunctional in a human cell line. What would be the predicted effect on translation?

• Translation stalls after the initiation AUG codon is identified.

• The ribosome cannot catalyze the formation of peptide bonds between the tRNAs in the A and P sites.

• The ribosome cannot interact with mRNAs.

• tRNAs cannot exit the E site of the ribosome.

Many antibiotics inhibit bacterial protein synthesis. For example, tetracycline blocks the A site on the bacterial ribosome, and chloramphenicol blocks peptidyl transfer. What specific effect would you expect each of these antibiotics to have on protein synthesis?

Tetracycline would directly affect:

• tRNA binding to the ribosome

• ribosome assembly

• growth of the protein chain

three-nucleotide sequence in a tRNA molecule that corresponds to an mRNA codon

• anticodon

• codon

• amino acid

• polypeptide