Biology 20A Module 2 Practice Midterm

Which of the following statements about the genetic code are true?

The genetic code is not ambiguous

The genetic code is universal

The genetic code is redundant

What is the role of DNA polymerase I?

Replaces primers with DNA

What is the role of helicase?

Unwinds the DNA double helix to expose the template strands

What is the role of primase?

Synthesizes the RNA primers required to begin the synthesis of DNA

What is the role of topoisomerase?

Prevents DNA from getting tangled up ahead of the replication fork

What is the role of DNA polymerase III?

The enzyme that synthesizes DNA beginning at the 3' end of a primer

What is the role of DNA ligase?

Covalently links Okazaki fragments

When a reaction yields a shorter DNA molecules covalently bound to short segments of RNA at their 5' ends, what was probably left out?

DNA polymerase I

What is true about capping and polyadenylation?

They can influence the stability and translation of mRNAs

Introns are removed from primary transcripts by:

The spliceosome

A mutation changes the termination codon of the mRNA encoding protein X from UAA to CCC.  What will be the consequence of this mutation?

One or more amino acids will be added to the C terminus of the protein X

What is associated with the DNA sequence?

trp operator, promoter

What is associated with the RNA sequence?

3’ untranslated region, iron-response element

What is associated with Proteins?

trp repressor, ferritin

A mutation in which of the following regions would probably have the greatest effect on the amino acid sequence of a protein encoded by a gene?

Coding region

The __________ determines which strand of DNA will be used as the template for transcription

Promoter

A mutation that changes a codon into a termination codon is a:

Nonsense mutation

Protein X is encoded by gene X.  In cancer cells, protein X is 125 amino acids in length.  In normal cells, protein X is 100 amino acids in length.  The N-terminal 75 amino acids and C terminal 25 amino acids of protein X are identical in normal and cancer cells.  Based on these data, which of the following are plausible explanations for why protein X is longer in cancer cells than normal cells:

In cancer cells, a mutation in a 5' splice site prevents the removal of a 75 base intron from the primary transcript of gene X

Humans have approximately 25,000 different genes that encode mRNAs but can produce a much larger number of different proteins.  Which of the following help explain this observation?

Alternative splicing allows some genes to encode more than one protein

During translation, ribosome moves from the _________ of an mRNA as the protein is synthesized from its ____________.

5’ to 3’ end, N to C terminus

True or false:  The coding region of a eukaryotic mRNA always corresponds to a single exon.

False

Which of the following catalyzes the formation of the peptide bond during protein synthesis?

The ribosome

The template strand is always:

3’ to '5’

What is associated with DNA replication?

origin

What is associated with Transcription?

promoter, operator

What is associated with RNA processing?

splicesome, intron

What is associated with Translation?

ribosome, release factor, tRNA

Which of the following specify the region of an mRNA that encodes a protein?

start and stop codons

What occurs when tryptophan levels are high in bacteria?

The trp repressor binds the operator and blocks the transcription of the trp operon

During transcription, RNA polymerase:

adds nucleotides to the 3' end of the growing RNA as it moves to the 5' end of the template strand

What adds the correct amino acid to a tRNA?

aminoacyl tRNA synthetase