Deck 6: Gene Expression: Translation

Question 1

A β-pleated sheet is a type of

A)primary structure found in a protein.
B)secondary structure found in a protein.
C)tertiary structure found in a protein.
D)quaternary structure found in a protein.
E)heme structure found in a protein.

Answer 1

B

Question 2

The majority of naturally occurring amino acids are

A)acidic and polar.
B)basic and nonpolar.
C)acidic and nonpolar.
D)neutral and nonpolar.
E)neutral and polar.

Answer 2

D

Question 3

Which of the following is not a characteristic of proteins?

A)High molecular weight
B)Presence of nitrogen
C)Presence of amino acids
D)Presence of nucleic acids
E)Structure built of one or more polypeptides

Answer 3

D

Question 4

In a gene sequence,the DNA codon for tryptophan experiences a mutation at the first base position,changing it to T.What will the resulting amino acid be?

A)Tryptophan (no change)
B)Serine
C)Arginine
D)Threonine
E)None (a stop codon will halt translation)

Question 5

How can a carrot plant express a bacterial gene?

A)Because the bacterial gene hijacks the carrot's cellular machinery
B)Because the genetic code is the same in both organisms
C)Because of the wobble phenomenon
D)Because of the degeneracy of the genetic code
E)A carrot cannot express a bacterial gene.

Question 6

Which of the following statements is not true of proteins destined for the ER?

A)They have a signal sequence.
B)The signal sequence for the ER consists of 15-30 amino acids.
C)The proteins are modified with carbohydrates in the ER.
D)The signal sequence is subsequently removed from the mature protein.
E)The SRP binds to the protein and prevents entry into the ER until translation is completed.

Question 7

In the genetic code,both AAU and AAC code for asparagine.For this reason,the code is said to be

A)degenerate.
B)nonspecific.
C)universal.
D)ambiguous.
E)wobbly.

Question 8

Which of the following events signals the termination of translation?

A)The ribosome reaches the end of the mRNA.
B)The ribosome reaches a start codon.
C)The ribosome reaches a stop codon.
D)The ribosome runs out of charged tRNAs.
E)The polypeptide chain folds into a protein.

Question 9

A mutation causes a G to be inserted after the first base of the codon for tryptophan.How will this affect the growing polypeptide chain?

A)It will not be affected.
B)Elongation will stop prematurely.
C)There will be a single amino acid substitution.
D)The reading frame will be shifted to the left,and the wrong amino acids will be added from this point on.
E)None of these

Question 10

Where does translation take place?

A)In the cytoplasm
B)In the nucleus
C)In the nucleolus
D)Anywhere in the cell
E)In the centriole

Question 11

How many naturally occurring amino acids are used by ribosomes to construct proteins?

A)46
B)64
C)3
D)20
E)10

Question 12

What is the basic shape of a tRNA molecule?

A)A three-dimensional cloverleaf
B)A straight strand
C)A right-handed helix
D)A globular ball
E)A β-pleated sheet

Question 13

In eukaryotes,the AUG initiation codon is located in the ________ sequence.

A)Shine-Dalgarno
B)Kozak
C)Khorana
D)Goldberg-Hogness
E)Pribnow

Question 14

Molecular chaperones

A)help guide proteins from the nucleus to the cytoplasm.
B)help guide proteins from the cytoplasm to the endoplasmic reticulum.
C)help fold proteins properly.
D)are proteins with structural function.
E)are proteins with enzymatic function.

Question 15

What is the role of tRNA in translation?

A)It brings together two subunits of a ribosome.
B)It couples an amino acid with aminoacyl-tRNA synthetase.
C)It helps fold up the finished polypeptide chain.
D)It catalyzes peptidyl transferase activity.
E)It binds to an mRNA codon and carries the corresponding amino acid.

Question 16

Every amino acid contains

A)an amino group and a hydroxyl group.
B)an amino group and an acetyl group.
C)a hydroxyl group and a carboxyl group.
D)a carboxyl group and an amino group.
E)a carboxyl group and a hydroxyl group.

Question 17

A peptide bond forms between the ________ of one amino acid and the ________ of another.

A)amino group,carboxyl group
B)amino group,R group
C)carboxyl group,sulfide group
D)amino group,phosphate group
E)R group,R group

Question 18

What is the function of a ribosome?

A)To direct transcription
B)To attach amino acids to the appropriate tRNAs
C)To unwind the double-stranded DNA helix to enable translation
D)To hold mRNA and tRNAs in the correct positions to enable translation
E)To make more mRNA

Question 19

The concept that a set of three nucleotides specifies a particular amino acid provides the basis for

A)the one-gene-one-enzyme hypothesis.
B)the one-gene-one-polypeptide hypothesis.
C)the genetic code.
D)biochemical reactions among nucleic acids.
E)All of these

Question 20

During translation,mRNA codons bind to complementary tRNA anticodons.

Question 21

Which of the following statements is correct?

A)For every codon,there is one amino acid.
B)For every amino acid,there is one codon.
C)A codon may signify more than one amino acid.
D)Three codons make up an amino acid.
E)Three amino acids make up a codon.

Question 22

A DNA codon reads GCC.Give the corresponding mRNA codon,tRNA anticodon,and amino acid.

Question 23

Molecules of mRNA are translated from 3' to 5',which is the opposite direction from which they were made.

Question 24

In the genetic code,when the first two nucleotides of a triplet are identical and the third letter is U or C,the codon always codes for the same amino acid.

Question 25

In the experiments performed on bacteriophage T4 by Francis Crick and others,in which it was shown that the genetic code was triplet,what were the researchers trying to identify?

Question 26

If a poly(C)is used as an mRNA and translated,a poly-glycine polypeptide is formed.If on the other hand a poly(G)mRNA is used,a poly-proline polypeptide is made.However,if both poly(C)and poly(G)are used in the same reaction,no polypeptide is made.Explain why.

Question 27

Why is methionine the first amino acid to be added to every polypeptide chain?

Question 28

What are the two sulfur-containing amino acids that contribute to a protein's tertiary structure?

Question 29

Part of a DNA gene sequence reads CAT.If a mutation occurs that changes the T to A,will the final protein be affected?

Question 30

There are 64 sense codons in the genetic code and 61 different types of tRNA molecules.

Question 31

When does quaternary structure occur?

Question 32

The genetic code is comma-free,nonoverlapping,and almost universal.

Question 33

A new initiation event cannot occur on an mRNA molecule until the first ribosome falls away.

Question 34

Protein synthesis begins when ribosomes bind to the UGA codon.

Question 35

The Shine-Dalgarno sequence is a purine-rich region just upstream of a start codon and is necessary for the initiation of protein synthesis in prokaryotes.

Question 36

If a tRNA anticodon reads GAI,to which mRNA codon(s)will it bind? What amino acid will the tRNA carry?

Question 37

Describe and differentiate among the primary,secondary,and tertiary structures of a protein.To which kinds of interactions can each of these stages be ascribed?

Question 38

With absolutely no exception,all organisms use the same genetic code for the production of proteins.

Question 39

In eukaryotes,the translation initiation complex forms in association with the 40S ribosomal subunit.

Question 40

Of the codons AAU,AUG,UAA,and UAU,which is considered a nonsense codon? What does this mean?

Question 41

How are proteins sorted into their appropriate cell compartments in eukaryotes?

Question 42

Would a two-letter code with four different nucleotides be sufficient to encode the 20 amino acids found in cells? Why or why not? What does the three-letter code imply about the nature of the genetic code?

Question 43

What is the wobble hypothesis,and what implications does it have for base-pairing rules and selective pressure on codons?

Question 44

Describe a cell-free protein synthesizing system with which you could determine unambiguously which codons specify which amino acids.

Question 45

How did von Ehrenstein et al.demonstrate that the specificity of codon recognition lies in the tRNA molecule and not in the amino acid it carries?