chapter 17 practice questions- complete by Friday 11/23/2011

Chapter 17 From Gene To Protein: Practice questions

Multiple Choice

Identify the letter of the choice that best completes the statement or answers the question.

____    1.   Base-pair substitutions involving the third base of a codon are unlikely to result in an error in the polypeptide. This is because

a.	substitutions are corrected before transcription begins.
b.	substitutions are restricted to introns.
c.	the base-pairing rules are less strict for the third base of codons and anticodons.
d.	a signal-recognition particle corrects coding errors.
e.	transcribed errors attract snRNPs, which then stimulate splicing and correction.

____    2.   In eukaryotic cells, transcription cannot begin until

a.	the two DNA strands have completely separated and exposed the promoter.
b.	several transcription factors have bound to the promoter.
c.	the 5' caps are removed from the mRNA.
d.	the DNA introns are removed from the template.
e.	DNA nucleases have isolated the transcription unit.

____    3.   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 does.
c.	It never codes for more than one amino acid.
d.	It extends from one end of a tRNA molecule.
e.	It is the basic unit of the genetic code.

____    4.   The metabolic pathway of arginine synthesis is as follows:

Precursor		Ornithine		Citrulline		Arginine
	A		B		C

Beadle and Tatum discovered several classes of Neurospora mutants that were able to grow on minimal medium with arginine added. Class I mutants were also able to grow on medium supplemented with either ornithine or citrulline, whereas class II mutants could grow on citrulline medium but not on ornithine medium. From the behavior of their mutants, Beadle and Tatum were able to conclude that

a.	one gene codes for the entire metabolic pathway.
b.	the genetic code of DNA is a triplet code.
c.	class I mutants have their mutations later in the nucleotide chain than do class II mutants.
d.	class I mutants have a nonfunctional enzyme at step A, and class II mutants have one at step B.
e.	class III mutants have nonfunctional enzymes for all three steps.

____    5.   The anticodon of a particular tRNA molecule is

a.	complementary to the corresponding mRNA codon.
b.	complementary to the corresponding triplet in rRNA.
c.	the part of tRNA that bonds to a specific amino acid.
d.	changeable, depending on the amino acid that attaches to the tRNA.
e.	catalytic, making the tRNA a ribozyme.

____    6.   Which of the following is not true of RNA processing?

a.	Exons are cut out before mRNA leaves the nucleus.
b.	Nucleotides may be added at both ends of the RNA.
c.	Ribozymes may function in RNA splicing.
d.	RNA splicing can be catalyzed by spliceosomes.
e.	A primary transcript is often much longer than the final RNA molecule that leaves the nucleus.

____    7.   Which of the following is true of translation in both prokaryotes and eukaryotes?

a.	Translation is coupled to transcription.
b.	The product of transcription is immediately ready for translation.
c.	The codon UUU codes for phenylalanine.
d.	Ribosomes are affected by streptomycin.
e.	The signal-recognition particle (SRP. binds to the first 20 amino acids of certain polypeptides.

Use the table of condons below to answer the following questions.

Use Diagram in book- stop and start codon diagram- The one with the chart!

____    8.   Using the genetic code in the table, identify a 5'  3' sequence of nucleotides in the DNA template strand for an mRNA coding for the polypeptide sequence Phe-Pro-Lys.

a.	UUU-GGG-AAA
b.	GAA-CCC-CTT
c.	AAA-ACC-TTT
d.	CTT-CGG-GAA
e.	AAA-CCC-UUU

____    9.   Which of the following mutations would be most likely to have a harmful effect on an organism?

a.	a base-pair substitution
b.	a deletion of three nucleotides near the middle of a gene
c.	a single nucleotide deletion in the middle of an intron
d.	a single nucleotide deletion near the end of the coding sequence
e.	a single nucleotide insertion downstream of, and close to, the start of the coding sequence

____  10.   Which component is not directly involved in translation?

a.	mRNA
b.	DNA
c.	tRNA
d.	ribosomes
e.	GTP