Biology 103 - Module 7 Study Guide
The total number of different three-base combinations of the four nucleic acid bases is:
64
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
What happens during nucleotide excision repair?
A nuclease removes the damaged DNA.
Translation is initiated at the ____.
AUG codon
Viruses that infect bacteria are known as?
Bacteriophages
Why is only one strand of DNA transcribed into mRNA?
Because transcribing both DNA strands would produce different amino acid sequences
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
When a mutation occurs during DNA replication, ____ replaces the incorrect nucleotide with the correct one after the mismatched nucleotide has been removed.
DNA polymerase
Refer to the accompanying figure. Which label indicates the location of the promoter region?
E
An RNA primer is synthesized by RNA primase.
False
demonstrated that genetic traits can be transferred from one bacterium to another
Griffith
discovered that the genetic material in bacteriophages is DNA
Hershey and Chase
used proteins labeled with 35S and DNA labeled with 32P to demonstrate that viral DNA entered bacterial cells, but viral proteins did not
Hershey and Chase
What conclusion was associated with mutant strain III in the accompanying figure?
It was missing the enzyme that catalyzes the conversion of citrulline to arginine.
grew bacteria in the presence of heavy nitrogen (15N), followed by growth in 14N medium for one or two generations, then measured the density of the DNA
Meselson and Stahl
What are special enzymes that recognize and remove the incorrectly paired nucleotides in DNA?
Mismatch repair
How many different kinds of amino acids are known?
More than 20
Proteins synthesized in bacteria have which of the following at their amino terminal end?
N-formyl-methionine
Neurospora is an ideal organism to study the effects of genetic mutations because of several reasons. What is one of these?
Neurospora mutant strains that cannot make a particular amino acid can still grow if that amino acid is added to the growth medium.
During translocation, the movement of the ribosome repositions the tRNA linked to the growing polypeptide chain to the ____ site, thereby vacating the ____ site for the arrival of a new amino-acyl tRNA.
P; A
Refer to the accompanying figure. The component labeled as B is:
RNA polymerase.
prevents the hydrolysis of single DNA strands by nucleases
Single-strand binding protein
Which of the following consists of short, noncoding, guanine-rich DNA sequences that repeat many times?
Telomere
____, the ends of eukaryotic chromosomes, shorten with every cell division.
Telomeres
How is the four-letter language of nucleic acids converted into the 20-word language of amino acids?
The four nucleic acid bases combine in three-letter sequences that define different amino acids.
How are eukaryotic chromosomes replicated?
The linear DNA molecules are replicated from multiple origins of replication bidirectionally.
Which of the following statements concerning DNA is FALSE?
The sugar present in DNA is ribose.
The notion that the genetic code is universal suggests a common ancestor for all living organisms.
True
Uracil forms a complementary pair with ____ in RNA and ____ in DNA.
adenine; adenine
Aminoacyl-tRNA synthetases link ____ to their respective tRNA molecules by ____ bonds.
codons; covalent
If DNA replication rejoined the two parental strands, it would be described as
conservative
Hydrogen bonds can form between guanine and ____, and between adenine and ____.
cytosine; thymine
protein synthesis proceeding in a 5' to 3' direction
elongation
assembly of the ribosome
initiation
Frameshift mutations result from the:
insertion or deletion of one or two base pairs
In DNA replication, the lagging strand
is synthesized as a series of Okazaki fragments
The DNA strand that is replicated smoothly and continuously is called the
leading strand.
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
In replication, once the DNA strands have been separated, reformation of the double helix is prevented by
single-strand binding proteins.
Individuals with mutations in excision repair enzymes may suffer from ____ due to unrepaired DNA damage caused by ____.
skin cancer; the sun's UV rays
responsible for pre-rRNA molecule processing in the nucleolus
snoRNA
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.
The molecule that connects a growing polypeptide chain and mRNA is called:
tRNA.
The ends of eukaryotic chromosomes can be lengthened by
telomerase
completed polypeptide chain released from ribosome
termination
triggered by a stop codon
termination
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
Errors in DNA replication can come from
DNA polymerase.
Why does DNA synthesis proceed in a 5′ to 3′ direction?
DNA polymerases can only add nucleotides to the 3′ end of a polynucleotide strand.
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.
The process in which RNA is synthesized using a DNA template is called translation.
False
The process of DNA replication is conservative.
False
The template DNA strand is described as being parallel to the complementary RNA strand.
False
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
X-ray diffraction images produced by ____ were used by Watson and Crick to infer the structure of DNA.
Franklin
Which of the following is a characteristic of uracil?
It has the ability to bond with adenine.
Why is DNA able to store large amounts of information?
Its nucleotides can be arranged in many possible sequences.
Who first confirmed that the replication of DNA was semiconservative?
Meselson and Stahl
demonstrated that DNA is replicated semiconservatively
Meselson and Stahl
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
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 is a bacterial chromosome replicated?
The circular DNA molecule is replicated from one origin of replication bidirectionally.
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.
Which of the following statements is FALSE with regard to DNA replication?
The strand being copied is read in the 5¢->3¢ direction.
produces breaks in the DNA molecules and then rejoins the strands to prevent supercoiling
Topoisomerase
A grouping of three nucleotides codes for one amino acid.
True
A(n) transposon is a DNA sequence that "jumps" into the middle of a gene.
True
Adenine and thymine are held together by two hydrogen bonds in a double stranded DNA molecule.
True
If you consider a DNA molecule to resemble a twisted ladder, the rungs of the ladder are paired nitrogen bases.
True
In mismatch repair, enzymes remove incorrectly-paired nucleotides.
True
In one strand of a DNA molecule, adjacent nucleotides are joined by a phosphodiester linkage.
True
In the process of transcription, incoming RNA nucleotides are in their triphosphates form.
True
RNA interference is a process by which noncoding RNA molecules regulate gene expression.
True
Reverse transcriptase catalyzes the synthesis of DNA from an RNA template.
True
Short, noncoding, guanine-rich DNA sequences found at the ends of chromosomes are called telomeres.
True
Signal-recognition particle RNA is involved in directing the ribosome-mRNA-polypeptide complex to the rough ER.
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
The poly-A tail is thought to facilitate the export of mRNA from the nucleus.
True
Which is a powerful method for determining the 3D structure of a molecule?
X-ray diffraction
What is the modern definition of a gene?
a DNA sequence that encodes a specific RNA or protein product
A polyribosome is:
a complex composed of several ribosomes and plus an mRNA transcript
In the Beadle and Tatum study, it was important that Neurospora was haploid because:
a mutation that arises is not masked by a normal allele on a homologous chromosome.
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.
Ribose differs from deoxyribose by having:
an extra hydroxyl group
Introns in pre-mRNA:
are spliced out of the message.
During protein synthesis, ribosomes:
attach to the mRNA molecule and travel along its length to produce a polypeptide
Unlike normal cells, cancerous cells
can maintain telomere length as they divide.
The wobble hypothesis states that:
certain tRNA anticodons can pair with more than one codon sequence.
X-ray diffraction studies are used to determine the
distances between atoms of molecules.
growth of the polypeptide chain
elongation
Binding of the appropriate aminoacyl-tRNA to the A site requires:
energy supplied by GTP
initiator tRNA binds to the start codon
initiation
the first stage of translation
initiation
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.
small RNA molecules; inhibit translation
miRNA
A mutation that replaces one amino acid in a protein with another is called a ____ mutation.
missense
Mobile genetic elements, such as transposons and retrotransposons, are significant because:
mutations caused by retrotransposons contribute greatly to a species' evolution.
A ____ mutation results in the conversion of a codon specifying an amino acid to a termination codon.
nonsense
The information encoded by the DNA is specified by the
nucleotide sequence of the DNA molecule.
DNA synthesis
occurs only once during each cell generation.
A nucleotide is made up of a phosphate group, a five-carbon sugar molecule, and
one of four nitrogeneous bases.
Because a newly synthesized DNA molecule contains ____, the replication process is said to be semiconservative.
one parental strand and one new strand
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
A "5′ cap":
protects mRNA from degradation.
Retroviruses, such as RNA tumor viruses, use __________ to make DNA from their RNA genomes.
reverse transcriptase
Peptidyl transferase, a _____ molecule, catalyzes the formation of _____ between amino acids at the P and A sites.
ribozyme; peptide bonds
small double-stranded RNA molecules; regulates gene expression miRNA
siRNA
RNA is ____ and contains the nitrogenous base ____, which is absent in DNA.
single stranded; uracil
The two molecules that alternate to form the backbone of a polynucleotide chain are
sugar and phosphate.
According to Chargaff's rules,
the adenine content in any DNA molecule is always equal to the thymine content.
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.
Linus Pauling demonstrated that:
the structure of hemoglobin was altered by a mutation of a single gene.
Enzymes called ____ form breaks in the DNA molecules to prevent the formation of knots in the DNA helix during replication.
topoisomerases
RNA synthesis is also known as:
transcription
The process illustrated in the accompanying figure is:
transcription
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.
In the experiments of Griffith, the conversion of nonlethal R-strain bacteria to lethal S-strain bacteria
was due to transformation.
discovered that DNA was responsible for bacterial transformation
Avery
The first scientists to use Griffith's transformation assay to identify genetic material were
Avery, MacLeod, and McCarty.
demonstrated the ratio of nucleotide bases in DNA
Chargaff
What allows each strand of DNA to serve as a template for a new DNA strand during replication?
Complementary base pairing between purines and pyrimidines on opposite strands
_____ bonds link the sugar and phosphate groups in the backbone of DNA molecules.
Covalent phosphodiester
Which of the following causes the unwinding of the DNA double helix?
DNA helicase
binds DNA at the origin of replication and breaks the hydrogen bonds between the paired bases
DNA helicase
opens the double helix like a zipper
DNA helices
catalyzes a reaction that occurs in the lagging strand but not in the leading strand
DNA ligase
catalyzes formation of sugar-phosphate bonds in adjacent Okazaki fragments
DNA ligase
Okazaki fragments are joined together by
DNA ligase.
In the accompanying figure, the portion of the molecule containing the anticodon is indicated by the label:
3
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′
A sequence of bases located upstream from a reference point occurs toward the:
5′ end of the mRNA sequence
What conclusions did Beadle and Tatum reach in their studies of Neurospora?
Each mutant gene affected only one enzyme.
A ribosome has one binding site for mRNA and two binding sites for tRNAs.
False
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
Linus Pauling proposed the one gene - one enzyme hypothesis.
False
Molecular chaperones assist in the folding of newly synthesized mRNAs.
False
Okazaki fragments are complementary to the leading strand of DNA.
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