Deck 13: Regulation of Gene Expression in Eukaryotes

Question 1

What makes up the initiation complex at the start of translation?

A) A large and a small ribosomal subunit
B) The small ribosomal subunit, an mRNA molecule, and an initiator tRNA molecule
C) The small ribosomal subunit and an mRNA molecule
D) A codon and an anticodon
E) The E site, the P site, and the A site

Answer 1

B

Question 2

Which of the following is a characteristic of protein?

A) Contains nitrogen
B) High molecular weight
C) Composed of nucleic acids
D) Both A and B
E) All of the above

Answer 2

D

Question 3

What is the function of a ribosome?

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

Answer 3

E

Question 4

Which of the following statements is correct?

A) For every amino acid, there is one codon.
B) For every codon, there is one amino acid.
C) A codon may signify more than one amino acid.
D) All of these are correct.
E) None of these are correct.

Question 5

The majority of naturally occurring amino acids are

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

Question 6

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

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

Question 7

An alpha helix and a beta-pleated sheet are types of

A) protein primary structure.
B) protein secondary structure.
C) tRNA secondary structure.
D) protein quaternary structure.
E) protein tertiary structure.

Question 8

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

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

Question 9

What signals the termination of translation?

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

Question 10

Where does translation take place?

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

Question 11

Which enzyme "charges" a tRNA molecule with the appropriate amino acid?

A) RNA polymerase
B) DNA polymerase
C) tRNA ligase
D) Aminoacyl-tRNA synthetase
E) Peptidyl transferase

Question 12

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

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

Question 13

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) The reading frame will be shifted to the left, and the wrong amino acids will be added from this point on.
C) There will be a single amino acid substitution.
D) Elongation will stop prematurely.
E) None of the above

Question 14

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

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

Question 15

What is the basic shape of a tRNA molecule?

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

Question 16

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

A) Arginine
B) Tryptophan (no change)
C) Threonine
D) Serine
E) A stop codon will halt translation.

Question 17

Why is it that a carrot plant can express a bacterial gene?

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

Question 18

Ribozymes in the large ribosomal subunit catalyze peptidyl transferase activity during elongation. What is the immediate result?

A) The tRNA in the P site falls off the ribosome.
B) The ribosome shifts by one codon toward the 3' end of the mRNA.
C) A new charged tRNA moves into the A site.
D) The bond is broken between the tRNA at the P site and its amino acid, and a peptide bond is formed between this amino acid and the one attached to the tRNA in the A site.
E) The elongation factor EF-Tu is recycled.

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

Question 20

What is the role of tRNA in translation?

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

Question 21

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

Question 22

Out of the following codons, which one is considered a nonsense codon? What does this mean? AAU, AUG, UAA, UAU

Question 23

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

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

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

Question 26

When does quaternary structure occur?

Question 27

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 28

Protein synthesis begins when ribosomes bind to the UGA codon.

Question 29

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

Question 30

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

Question 31

Describe the basic structure of an amino acid.

Question 32

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

Question 33

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

Question 34

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

Question 35

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

Question 36

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

Question 37

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

Question 38

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

Question 39

During translation, mRNA codons bind to complementary tRNA anticodons.

Question 40

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

Question 41

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

Question 42

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

Question 43

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?