Module 7
The total number of different three-base combinations of the four nucleic acid bases is:
64
Viruses that infect bacteria are known as?
Bacteriophages
The 3' trailing sequences are located upstream of the stop codon.
False
The process of DNA replication is conservative.
False
If you consider a DNA molecule to resemble a twisted ladder, the rungs of the ladder are paired nitrogen bases.
True
In one strand of a DNA molecule, adjacent nucleotides are joined by a phosphodiester linkage.
True
Reverse transcriptase catalyzes the synthesis of DNA from an RNA template.
True
The poly-A tail is thought to facilitate the export of mRNA from the nucleus.
True
A "5′ cap":
protects mRNA from degradation.
small double-stranded RNA molecules; regulates gene expression
siRNA
In replication, once the DNA strands have been separated, reformation of the double helix is prevented by
single-strand binding proteins.
responsible for pre-rRNA molecule processing in the nucleolus
snoRNA
RNA synthesis is also known as:
transcription
What happens during nucleotide excision repair?
A nuclease removes the damaged DNA.
catalyzes the synthesis of an RNA primer at both leading and lagging strand
DNA primase
Alfred Hershey's and Martha Chase's experiments with bacteriophages showed that
DNA was injected into bacteria.
An RNA primer is synthesized by RNA primase.
False
Okazaki fragments are complementary to the leading strand of DNA
False
Proteins synthesized in bacteria have which of the following at their amino terminal end?
N-formyl-methionine
____, the ends of eukaryotic chromosomes, shorten with every cell division.
Telomeres
How is a bacterial chromosome replicated?
The circular DNA molecule is replicated from one origin of replication bidirectionally.
Which of the following statements concerning DNA is FALSE?
The sugar present in DNA is ribose
During protein synthesis, ribosomes:
attach to the mRNA molecule and travel along its length to produce a polypeptide
Hydrogen bonds can form between guanine and ____, and between adenine and ____
cytosine; thymine
Because a newly synthesized DNA molecule contains ____, the replication process is said to be semiconservative.
one parental strand and one new strand
tRNA molecules are able to act as adapters between amino acids and mRNA during translation because:
tRNA can bind to both mRNA and an amino acid.
If an mRNA transcript of the human XYZ gene was introduced into a yeast cell, the transcript would be:
translated into the human XYZ protein
When a mutation occurs during DNA replication, ____ replaces the incorrect nucleotide with the correct one after the mismatched nucleotide has been removed.
DNA polymerase
adds nucleotides only to the 3¢ end of an existing polynucleotide strand
DNA polymerase
joins successive nucleotides to a growing polynucleotide strand, complementary to the template strand
DNA polymerase
The two strands of a DNA double helix can be described as running parallel to each other.
False
snRNPs function to splice introns together.
False
Who first confirmed that the replication of DNA was semiconservative?
Meselson and Stahl
How many different kinds of amino acids are known?
More than 20
What are the small circular DNA molecules that carry genes separate from those on a bacterial chromosome?
Plasmids
helps to deliver the ribosome-mRNA-polypeptide complex to the rough ER
SRP RNA
prevents formation of hydrogen bonds between complementary base pairs
Single-strand binding protein
prevents the hydrolysis of single DNA strands by nucleases
Single-strand binding protein
What happened in an experiment where normal cultured human cells were infected with a virus that carried DNA encoding for the telomerase catalytic subunit?
The cells underwent more cell divisions than normal
How does the first nucleotide at the 5′ end of a new mRNA chain differ from the other nucleotides in the chain?
The first nucleotide retains its triphosphate group, while the others do not.
produces breaks in the DNA molecules and then rejoins the strands to prevent supercoiling
Topoisomerase
In one strand of a DNA molecule, adjacent nucleotides are joined by a phosphodiester linkage
True
Which is a powerful method for determining the 3D structure of a molecule?
X-ray diffraction
Initiation of transcription requires:
a promoter sequence
The 3′ end of eukaryotic pre-mRNAs is changed by:
adding 100−250 adenine nucleotides
Leader sequences contain signals that:
allow the ribosomes to be properly positioned for translation of mRNA molecules.
Aminoacyl-tRNA synthetases link ____ to their respective tRNA molecules by ____ bonds.
codons; covalent
large RNA molecules; regulates chromatin structure
lncRNA
Primase is the enzyme responsible for
making short strands of RNA at the site of replication initiation.
Garrod first proposed that
metabolic defects were due to the lack of an enzyme
Garrod first proposed that:
metabolic defects were due to the lack of an enzyme.
A mutation that replaces one amino acid in a protein with another is called a ____ mutation.
missense
Following peptide bond formation between the amino acid in the A site on the ribosome and the growing polypeptide chain, the tRNA in the A site:
moves to the P site of the ribosome
The information encoded by the DNA is specified by the
nucleotide sequence of the DNA molecule.
These noncoding sequences located within coding regions of ____ genes are called ____.
only eukaryotic; introns
small RNA molecules; inhibits mobile DNA element activity in germ cells
piRNA
Peptidyl transferase, a _____ molecule, catalyzes the formation of _____ between amino acids at the P and A sites.
ribozyme; peptide bonds
RNA is ____ and contains the nitrogenous base ____, which is absent in DNA.
single stranded; uracil
The molecule that connects a growing polypeptide chain and mRNA is called:
tRNA
opens the double helix like a zipper
DNA helicase
The first scientists to use Griffith's transformation assay to identify genetic material were
Avery, MacLeod, and McCarty.
Errors in DNA replication can come from
DNA polymerase
What conclusions did Beadle and Tatum reach in their studies of Neurospora?
Each mutant gene affected only one enzyme
Which of the following numbered events represents the correct sequence of events of prokaryotic translation initiation? 1) Large ribosomal subunit binds to initiation complex. 2) Initiation tRNA binds small ribosomal subunit. 3) Initiation complex binds to ribosome recognition sequence on mRNA.
2 → 3 → 1
One of the mRNA codons specifying the amino acid leucine is 5′-CUA-3′. Its corresponding anticodon is:
3′-GAU-5′
Which of the following nucleotide sequences represents the complement to the DNA strand, 5′-AGATCCG-3′?
3′-TCTAGGC-5′
Beadle and Tatum began their studies with wild-type Neurospora. How is this organism best characterized?`
A normal phenotype that will grow on minimal medium
Translation is initiated at the ____.
AUG codon
Beadle and Tatum irradiated Neurospora and initially grew the mutant strains on complete medium. How were they able to determine the type of mutation for each strain?
By growing the mold on minimal media supplemented with different combinations of amino acids and vitamins
binds DNA at the origin of replication and breaks the hydrogen bonds between the paired bases
DNA helicase
Catalyzes formation of sugar-phosphate bonds in adjacent Okazaki fragments
DNA ligase
Okazaki fragments are joined together by
DNA ligase
catalyzes a reaction that occurs in the lagging strand but not in the leading strand
DNA ligase
Refer to the accompanying figure. Which label indicates the location of the promoter region?
E
A(n) nonsense mutation is a base-pair substitution that results in the replacement of one amino acid with another.
False
DNA Pol III catalyzes the addition of successive nucleotides to the 5' end of a growing polynucleotide chain
False
In eukaryotes, the initiator tRNA carries the amino acid leucine.
False
One function of snoRNAs is to process pre-rRNA molecules in the mitochondrion.
False
One of the pyrimidine bases in a DNA molecule is adenine.
False
RNA polymerase binds to the promoter sequence in RNA.
False
Replication typically occurs at a single origin of replication in eukaryotic chromosomes.
False
The process in which RNA is synthesized using a DNA template is called translation
False
The process in which RNA is synthesized using a DNA template is called translation.
False
Why is DNA able to store large amounts of information?
Its nucleotides can be arranged in many possible sequences
Refer to the accompanying figure. The component labeled as B is:
RNA polymerase.
Which of the following consists of short, noncoding, guanine-rich DNA sequences that repeat many times?
Telomere
Short, noncoding, guanine-rich DNA sequences found at the ends of chromosomes are called telomeres.
True
Single-strand binding proteins prevent the hydrolysis of single-strand regions of DNA by nucleases.
True
The enzyme peptidyl transferase catalyzes peptide bond formation during the elongation stage of translation
True
To fit X-ray crystallographic data, the two DNA strands in Watson and Crick's model must be ____ to each other
antiparallel
To fit X-ray crystallographic data, the two DNA strands in Watson and Crick's model must be ____ to each other.
antiparallel
Which of the following is made from DNA?
mRNA, tRNA, rRNA
small RNA molecules; inhibit translation
miRNA
A ____ mutation results in the conversion of a codon specifying an amino acid to a termination codon.
nonsense
A nucleotide is made up of a phosphate group, a five-carbon sugar molecule, and
one of four nitrogeneous bases.
Individuals with mutations in excision repair enzymes may suffer from ____ due to unrepaired DNA damage caused by ____.
skin cancer; the sun's UV rays
From the DNA X-ray crystallography data, Franklin and Wilkins inferred that ____, while Watson and Crick determined that ____.
the flat nucleotide bases are stacked upon each other; DNA is helical
The experimental design in the accompanying figure was used to examine:
the relationship between genetic changes and metabolic enzymes
The process illustrated in the accompanying figure is:
transcription
