Deck 9: The Chemistry of Heredity and Gene Expression

Question 1

A codon consists of _____ nucleotides in a(n) ____ molecule.

A) two; DNA
B) three; DNA
C) four; DNA
D) three; RNA
E) four; RNA

Answer 1

D

Question 2

Each strand in a DNA molecule:

A) is bonded to two other strands.
B) has a 5′ end and a 3′ end.
C) has two 5′ ends.
D) has two 3′ ends.
E) is parallel to the other strand(s) but not antiparallel.

Answer 2

B

Question 3

DNA replication requires a short strand of _____ as a primer to initiate synthesis.

A) carbohydrates
B) amino acids
C) phospholipids
D) RNA
E) magnesium ions

Answer 3

D

Question 4

The role of ______ is to carry amino acids to the ribosomes.

A) DNA
B) mRNA
C) tRNA
D) rRNA
E) protein

Question 5

Which of the following statements about DNA replication in eukaryotes is FALSE?

A) It is a bidirectional process.
B) Helicases break the hydrogen bonds at the origin of replication.
C) DNA polymerases catalyze the synthesis of the new strands.
D) The two replication forks move in opposite directions away from the origin.
E) There is only one origin of replication.

Question 6

The process of translation results in the synthesis of:

A) DNA.
B) mRNA.
C) tRNA.
D) rRNA.
E) protein.

Question 7

The pyrimidine bases of DNA are:

A) cytosine and thymine.
B) cytosine and adenine.
C) adenine and guanine.
D) guanine and cytosine.
E) guanine and thymine.

Question 8

In the ladder analogy of DNA structure, the sides of the ladder are composed of:

A) sugars.
B) phosphates.
C) alternating sugars and phosphates.
D) alternating sugars and nitrogenous bases.
E) nitrogenous bases.

Question 9

In a DNA molecule, the hydrogen bonds join:

A) the paired nitrogenous bases.
B) sugars and phosphates.
C) sugars and nitrogenous bases.
D) phosphates and nitrogenous bases.
E) pairs of sugars.

Question 10

When scientists describe the genetic code as redundant, they mean that:

A) it becomes disorganized over time.
B) many amino acids have more than one codon.
C) some codons specify stop signals.
D) it varies with cell type.
E) it varies among species.

Question 11

RNA contains ______ instead of the ______ found in DNA.

A) adenine; thymine
B) uracil; thymine
C) adenine; uracil
D) guanine; cytosine
E) uracil; guanine

Question 12

Data obtained by Erwin Chargaff indicated that in DNA the ratio of nucleotides containing _________ to those containing _______ is approximately 1:1.

A) adenine; cytosine
B) adenine; thymine
C) guanine; thymine
D) thymine; cytosine
E) guanine; adenine

Question 13

A transfer RNA molecule carries a(n) ______ to the ribosomes.

A) amino acid
B) protein
C) mRNA molecule
D) ATP molecule
E) segment of DNA nucleotides

Question 14

Which of the following statements about promoters is FALSE?

A) They are specific nucleotide sequences of DNA.
B) They consist of three nucleotides that bind to a codon.
C) They determine the position where RNA synthesis begins.
D) They determine which DNA strand is used as a template.
E) They are binding sites for RNA polymerase.

Question 15

In DNA replication, _______ catalyzes the joining of Okazaki fragments.

A) single-strand binding protein
B) DNA ligase
C) histone
D) DNA polymerase
E) helicase

Question 16

In DNA replication, the lagging strand differs from the leading strand in that the lagging strand is synthesized:

A) in a 5′ to 3′ direction.
B) in a 3′ to 5′ direction.
C) in fragments.
D) using DNA polymerase.
E) outside the replication bubble.

Question 17

Which of the following molecules contains an anticodon?

A) DNA
B) mRNA
C) tRNA
D) rRNA
E) protein

Question 18

The DNA molecule has the shape of a:

A) single helix.
B) double helix
C) triple helix.
D) step ladder.
E) staircase.

Question 19

After a DNA molecule "unzips," the two strands are kept separated by:

A) single-strand binding proteins.
B) DNA polymerase.
C) DNA ligase.
D) helicases.
E) telomerase.

Question 20

Which of the following are complementary bases?

A) adenine and cytosine
B) adenine and guanine
C) thymine and cytosine
D) guanine and cytosine
E) thymine and guanine

Question 21

An incoming aminoacyl-tRNA molecule binds to the ribosome at the ______ site.

A) A (aminoacyl)
B) mRNA-binding
C) P (peptidyl)
D) E (exit)
E) promoter

Question 22

Which of the following events is NOT part of the initiation stage of translation?

A) The smaller ribosomal subunit attaches to mRNA.
B) GTP is hydrolyzed.
C) The larger ribosomal subunit attaches to the smaller subunit.
D) fMet-tRNA binds at the P site.
E) The initiator tRNA is released from the E site.

Question 23

When DNA is methylated:

A) transcription is repressed.
B) transcription is stimulated.
C) histone tails bind DNA.
D) histone tails are released from DNA.
E) histones are acetylated.

Question 24

During the elongation stage of translation:

A) the two ribosomal subunits separate.
B) a polysome forms.
C) release factors bind at the A site.
D) fMet-tRNA binds to the initiation codon.
E) a peptide bond is formed.

Question 25

Polypeptides destined for membranes of the Golgi complex are synthesized on ribosomes:

A) that are free in the cytosol.
B) attached to the endoplasmic reticulum.
C) in the nucleus.
D) in mitochondria.
E) in plastids.

Question 26

In a cell of a multicellular organism:

A) all enzymes are expressed continuously.
B) some genes are expressed continuously.
C) some genes are not expressed.
D) some genes are switched "on" at certain times.
E) some genes are switched "off" at certain times.

Question 27

Which of the following statements concerning transposons is FALSE?

A) They are "molecular parasites."
B) They replicate more slowly than other genes.
C) They can be inserted into host genes.
D) Eukaryotes have epigenetic mechanisms for silencing them.
E) They can increase in number from one cell generation to the next.

Question 28

Interspersed repeated DNA units:

A) are arranged in tandem.
B) tend to be smaller than 10 base pairs long.
C) constitute less than 10 percent of the DNA of most multicellular organisms.
D) are identical to one another.
E) are believed to have originated from transposons.

Question 29

Which of the following events occurs in eukaryotic cells but NOT in prokaryotic cells?

A) RNA polymerase attaches to a particular nucleotide sequence on the DNA.
B) RNA is synthesized using the 3′ to 5′ DNA strand as a template.
C) Two or more structural genes are transcribed onto a single RNA molecule.
D) mRNA transcripts are extensively modified before they leave the nucleus.
E) tRNAs, rRNAs, and mRNAs are all involved in the translation process.

Question 30

Which of the following statements about simple-sequence repeated DNA segments is FALSE?

A) They are tandemly repeated.
B) They occur in telomeres.
C) They are dispersed throughout the DNA.
D) They occur in centromeres.
E) They have fewer than 10 base pairs.

Question 31

A ribosome consists of ______ and ______.

A) DNA; mRNA
B) mRNA; protein
C) mRNA; tRNA
D) rRNA; mRNA
E) rRNA; protein

Question 32

Which of the following is the best estimate for the percentage of DNA in eukaryotic cells that codes for proteins?

A) less than 1 percent
B) less than 10 percent
C) about 25 percent
D) about 50 percent
E) about 75 percent

Question 33

Which of the following statements concerning telomeres is FALSE?

A) They consist of simple-sequence repeated DNA.
B) They are located at the ends of the chromosomes.
C) They serve as caps.
D) They are regions of active transcription.
E) They protect the chromosome from degradation.

Question 34

Euchromatin differs from heterochromatin in that euchromatin:

A) stains more strongly.
B) is more tightly condensed.
C) predominates in centromeres.
D) predominates in telomeres.
E) is more readily transcribed during interphase.

Question 35

Which of the following events is NOT involved in mRNA processing?

A) the addition of a 5′ "cap"
B) the addition of a poly-A tail
C) the forming of peptide bonds
D) the splicing together of exons
E) the removal of introns

Question 36

An aminoacyl-tRNA synthetase catalyzes the:

A) attachment of a particular tRNA to mRNA.
B) binding of RNA polymerase to the terminator.
C) binding of RNA polymerase to the promoter.
D) attachment of a particular amino acid to a particular tRNA.
E) attachment of a particular tRNA to the ribosome.

Question 37

Which of the following statements concerning noncoding RNAs is FALSE?

A) They are types of tRNA molecules.
B) They are present in most eukaryotic genomes.
C) Some are responsible for striking developmental abnormalities.
D) An example is microRNA.
E) Some are responsible for RNA interference.

Question 38

Which of the following events is NOT part of the termination stage of translation?

A) The ribosome encounters a stop codon.
B) Release factors bind at the A site.
C) The ribosome moves along the mRNA to the next codon.
D) The ribosomal subunits separate.
E) The polypeptide chain is released.

Question 39

Acetyltransferases catalyze the attachment of acetyl groups to:

A) DNA.
B) ribosomes.
C) histones.
D) mRNA.
E) tRNA.

Question 40

Exons are segments of a gene that:

A) are transcribed into segments of mRNA that are snipped out before translation.
B) occur in prokaryotic but not eukaryotic chromosomes.
C) consist of RNA rather than DNA nucleotides.
D) are not transcribed by RNA polymerase.
E) are translated into protein.

Question 41

The function of aminoacyl-tRNA synthetase is to catalyze the synthesis of tRNA.

Question 42

The most abundant interspersed repeat sequences are transposons.

Question 43

Epigenetic inheritance refers to the inheritance of traits encoded by genes in the telomeres.

Question 44

DNA polymerase synthesizes new DNA strands only in the 5′ to 3′ direction.

Question 45

The genetic code in prokaryotes is different from that in eukaryotic cells.

Question 46

The two major categories of repeated DNA are tandemly repeated DNA and interspersed repeated DNA.

Question 47

In a plant, root cells have the same genetic composition as leaf cells.

Question 48

Simple-sequence repeated DNA occurs throughout the genome except at the centromeres and telomeres.

Question 49

The "primer" that initiates DNA replication is composed of RNA.

Question 50

When DNA is methylated, transcription is stimulated.

Question 51

RNA contains thymine instead of uracil.

Question 52

In DNA replication, the leading strand is synthesized in fragments, called Okazaki fragments, while the lagging strand is synthesized continuously.

Question 53

The incoming amino-acid-bearing tRNA binds at the A site.

Question 54

Exons are noncoding sequences of nucleotides that are present in genes.

Question 55

Peptide bond formation on the ribosome is catalyzed by RNA.

Question 56

The complementarity of the two strands of DNA is a direct result of A pairing only with T and C pairing only with G.

Question 57

The two strands of a DNA molecule are said to be antiparallel, each strand having its 5′ end at the same end of the molecule.

Question 58

Histone acetylation neutralizes the histone tails, and consequently transcription is repressed.

Question 59

In the ladder molecule of a DNA molecule, the purine and pyrimidine bases comprise the sides of the ladder.

Question 60

Heterochromatin is more tightly condensed than euchromatin and in some regions is never transcribed.

Question 61

Most eukaryotic structural genes contain introns.

Question 62

Before transcription is completed, a poly-A tail is added to the 3′ end of the mRNA.

Question 63

The 5′ cap of mRNA serves to bind the mRNA molecule to the ribosome.

Question 64

An example of a noncoding RNA is tRNA.