The AUC and AUA codons in mRNA both specify isoleucine. What feature of the genetic code explains this?
- nonsense codons
How many nucleotides are in 12 mRNA codons?
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 subunit of the E. coli polymerase confers specificity to transcription?
The -10 and -35 regions of prokaryotic promoters are called consensus sequences because ________.
- they are identical in all bacterial species
- they are similar in all bacterial species
- they exist in all organisms
- they have the same function in all organisms
Three different bacteria species have the following consensus sequences upstream of a conserved gene.
|Species A||Species B||Species C|
Order the bacteria from most to least efficient initiation of gene transcription.
- A > B > C
- B > C > A
- C > B > A
- A > C > B
Which feature of promoters can be found in both prokaryotes and eukaryotes?
- GC box
- TATA box
- octamer box
- -10 and -35 sequences
What transcripts will be most affected by low levels of α-amanitin?
- 18S and 28S rRNAs
- 5S rRNAs and tRNAs
- other small nuclear RNAs
How do enhancers and promoters differ?
- 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.
- Promoters bind transcription factors to increase the efficiency of transcription. 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
- 7-methylguanosine cap
What processing step enhances the stability of pre-tRNAs and pre-rRNAs?
- nucleotide modification
A scientist identifies a pre-mRNA with the following structure.
What is the predicted size of the corresponding mature mRNA in base pairs (bp), excluding the 5’ cap and 3’ poly-A tail?
The RNA components of ribosomes are synthesized in the ________.
- endoplasmic reticulum
In any given species, there are at least how many types of aminoacyl tRNA synthetases?
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.