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