quiz 10

How many nucleotides are in 12 mRNA codons? A. 36 B. 24 C. 48 D. 12

A. 36

Which feature of promoters can be found in both prokaryotes and eukaryotes? A. -10 and -35 sequences B. octamer box C. TATA box D. GC box

C. TATA box

What are exons? A. Untranslated DNA sequences in a gene B. DNA sequences to which polymerases bind C. Translated DNA sequences in a gene D. The processed mRNA

C. Translated DNA sequences in a gene

The anticodon of a particular tRNA molecule is A. the part of tRNA that bonds to a specific amino acid. B. complementary to the corresponding triplet in rRNA. C. complementary to the corresponding mRNA codon. D. changeable, depending on the amino acid that attaches to the tRNA.

C. complementary to the corresponding mRNA codon.

Which pre-mRNA processing step is important for initiating translation? A. 7-methylguanosine cap B. splicing C. RNA editing D. poly-A tail

A. 7-methylguanosine cap

The AUC and AUA codons in mRNA both specify isoleucine. What feature of the genetic code explains this? A. degeneracy B. universality C. complementarity D. nonsense codons

A. degeneracy

In eukaryotic cells, transcription cannot begin until A. several transcription factors have bound to the promoter. B. the two DNA strands have completely separated and exposed the promoter. C. the 5' caps are removed from the mRNA. D. the DNA introns are removed from the template.

A. several transcription factors have bound to the promoter.

Which subunit of the E. coli polymerase confers specificity to transcription? A. σ B. β C. α D. β'

A. σ

Which event contradicts the central dogma of molecular biology? A. Codons specifying amino acids are degenerate and universal. B. Scientists use reverse transcriptase enzymes to make DNA from RNA. C. Endonuclease enzymes splice out and repair damaged DNA. D. Poly-A polymerase enzymes process mRNA in the nucleus.

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

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? A. The ribosome cannot interact with mRNAs. B. Translation stalls after the initiation AUG codon is identified. C. The ribosome cannot catalyze the formation of peptide bonds between the tRNAs in the A and P sites. D. tRNAs cannot exit the E site of the ribosome.

B. Translation stalls after the initiation AUG codon is identified.

Which of the following mutations would be most likely to have a harmful effect on an organism? A. a nucleotide-pair substitution B. a single nucleotide insertion downstream of, and close to, the start of the coding sequence C. a single nucleotide deletion in the middle of an intron D. a deletion of three nucleotides near the middle of a gene

B. a single nucleotide insertion downstream of, and close to, the start of the coding sequence

In any given species, there are at least how many types of aminoacyl tRNA synthetases? A. 200 B. 40 C. 20 D. 100

C. 20

Which component is not directly involved in translation? A. tRNA B. mRNA C. DNA D. ribosomes

C. DNA

Which of the following is not true of a codon? A. It consists of three nucleotides. B. It may code for the same amino acid as another codon. C. It extends from one end of a tRNA molecule. D. It never codes for more than one amino acid.

C. It extends from one end of a tRNA molecule.

How do enhancers and promoters differ? A. There is no difference. Both are transcription factor-binding sequences in DNA. B. Promoters bind transcription factors to increase the efficiency of transcription. Enhancers bind RNA polymerases to initiate transcription. C. DNA D. Enhancers increase the efficiency of gene expression but are not essential for transcription. Promoter recognition is essential to transcription initiation.

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

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

D. Exons are cut out before mRNA leaves the nucleus.

What processing step enhances the stability of pre-tRNAs and pre-rRNAs? A. Splicing B. Nucleotide modification C. Cleavage D. Methylation

D. Methylation

What are introns? A. DNA sequences to which polymerases bind B. Translated DNA sequences in a gene C. The processed mRNA D. Untranslated DNA sequences in a gene

D. Untranslated DNA sequences in a gene

The RNA components of ribosomes are synthesized in the ________. A. cytoplasm B. endoplasmic reticulum C. nucleus D. nucleolus

D. nucleolus

What transcripts will be most affected by low levels of α-amanitin? A. 18S and 28S rRNAs B. other small nuclear RNAs C. 5S rRNAs and tRNAs D. pre-mRNAs

D. pre-mRNAs

The -10 and -35 regions of prokaryotic promoters are called consensus sequences because ________. A. they have the same function in all organisms B. they are identical in all bacterial species C. they exist in all organisms D. they are similar in all bacterial species

D. they are similar in all bacterial species

A poly-A sequence is added at the: A. 3'-end of a transcript in the cytoplasm B. 3'-end of a transcript in the nucleus C. 5' end of a transcript in the nucleus D. 5' end of a transcript in the cytoplasm

not a

What is the flow of information for the synthesis of proteins according to the central dogma? A. DNA to mRNA to tRNA to protein B. mRNA to DNA to mRNA to protein C. DNA to protein to mRNA to protein D. DNA to mRNA to protein

not a

Which of the following is associated with the docking of mRNA on a ribosome in eukaryotic cells? A. Shine-Dalgarno sequence B. Poly-A sequence C. Kozak's sequence D. TATA box

not a

The sequence that signals the end of transcription is called the: A. Stop codon B. Promoter C. TATA box D. Terminator

not d