Biology Lecture 12 Clicker Questions

The amino acid forms a peptide bond with the growing peptide chain when it is in which site. A. A B. P C. E D. That mRNA looks like a tapeworm

A. A

MCAT question: If a portion of prokaryotic mRNA has the base sequence: 5' - ACUACUAUGCGUCGA-3' What could be the result from a mutation whereby the underlined base changed to A? I. truncation of the polypeptide II. Inhibition of initiation of translation III. No effect on protein synthesis A. I and II only B. I and III only C. II and III only D. III only E. All possible

A. I and II only

The sequence shown is at the beginning of an mRNA. If the shown mutation were to happen (C->G @ bp 15), what would be the effect? 5' AUG GUC CAC CCC UAC CUC CGG UGA 3' A. Translation would terminate early B. Transcription would continue longer C. You'd get three extra amino acids D. Translation wouldn't stop E. Transcription would terminate early

A. Translation would terminate early

There are 61 mRNA codons that specify an amino acid, but only 45 tRNAs. This is best explained by the fact that... A) some tRNAs have anticodons that recognize four or more different codons. B) the rules for base pairing between the third base of a codon and tRNA are flexible. C) many codons are never used, so the tRNAs that recognize them are dispensable. D) the DNA codes for all 61 tRNAs but some are then destroyed. E) competitive exclusion forces some tRNAs to be destroyed by nucleases.

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

MCAT Q: A ribosome has made a tri-peptide methionine-arginine-serine, which is attached to the tRNA in the P site. What codon is in the E-site? A. AUG B. CGU C. UCA D. UGA

B. CGU

This is the beginning of an mRNA. Insertion of a U (between the U and C) would mean what for the mRNA? 5' AUG CUC UUC CUG AAA CAC 3' A. It would be silent because UUU and UUC both code for phenylalanine B. It would change the reading frame - a frame shift C. It would insert a premature stop codon (nonsense). D. It depends on which protein this is for. More than one

B. It would change the reading frame - a frame shift

The gene model above is for a eukaryotic protein. Blue sections are exons and brown are introns. If you wished to make this protein in the popular lab bacterium E. coli. What would you have to do? Pick as many numbers as you think are necessary. A. Insert the gene in the bacterial genome B. Treat the mRNA with reverse transcriptase (RNA DNA) and insert that in the bacterial genome C. Isolate the mRNA and insert that in the genome D. Add a bacterial promoter and 3'UTR

B. Treat the mRNA with reverse transcriptase (RNA DNA) and insert that in the bacterial genome D. Add a bacterial promoter and 3'UTR

You can run protein on a gel in a way very similar to DNA smaller goes to the bottom, modifications change molecular weight. The relative migration of DNA and protein is irrelevant so don't compare size between the gels, it's meaningless. What type of mutation could have produced these results? 1. Frameshift mutation 2. Nonsense mutation 3. Missense mutation 4. Silent mutation A. 1-4 B. 1,3 C. 1,2 D. 2,3 E. 2

C. 1,2

Which of the following is NOT a silent mutation? A. UUA-> UUG B. CUU->CUG C. AUG -> AUU D. UAG->UGA E. Like a troop of baboons, they're all silent.

C. AUG -> AUU

The following is a piece of mRNA from the middle of an exon. Can you tell what the first amino acid from this sequence would be? 5'AGUCUUACCGCAUUGUGG-3' A.Serine B. Valine C. Can't tell D. Won't tell E. I just don't know

C. Can't tell

AUG codes for methionine. What might happen if a mistake added another A after the first one (so now it's AAUG)? A. Nothing, because the tRNA would still recognize the codon for methionine. B. It would cause the other codons to be read differently. C. It depends where in the mRNA this happens. D. AUG is the start codon, so the protein would never get translated. E. None of the above.

C. It depends where in the mRNA this happens.

Which of the following occurs as the ribosome shifts down the mRNA by a distance of one codon? A. the tRNA that was in the A site picks up another amino acid B. tRNA that was in the A site releases the growing polypeptide chain C. the tRNA that was in the A site moves into the P site D. the tRNA that was in the P site moves into the A site E. the tRNA that was in the P site picks up another amino acid

C. the tRNA that was in the A site moves into the P site

This is the beginning of the translated part of an mRNA. Substitution of an A (for the underlined C) would mean what for the protein? 5' AUG CUC UUC CUG AAA CAC 3' A. It would be silent because UUU and UUC both code for phenylalanine B. It would change the reading frame - a frame shift C. It would insert a premature stop code (nonsense). D. It would change the amino acid, but otherwise the protein would be the same.

D. It would change the amino acid, but otherwise the protein would be the same.