Biology

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The toxin ricin can be fatal; it works by
a. breaking peptide bonds and destroying healthy proteins.
b. killing the cell by blocking protein synthesis.
c. blocking the synthesis of bacterial cell walls.
d. producing a lethal toxin that affects mRNA and ribosomal movement.
e. inhibiting the translocation of mRNA along the ribosome.

killing the cell by blocking protein synthesis

Genetic material is composed of
a. DNA.
b. amino acids.
c. ribose.
d. carbohydrates.
e. lipids.

DNA

The major phenotypic expression of genotype is in
a. proteins.
b. tRNA.
c. mRNA.
d. nucleic acids.
e. a mutation

proteins.

Which of the following are model organisms used in biological research?
a. Pea plants
b. Fruit flies
c. E. coli
d. Bread mold
e. All of the above

All of the above

After irradiating Neurospora, Beadle and Tatum collected mutants that would
a. not grow on a minimal medium but would grow on a minimal medium with arginine.
b. grow on any minimal medium.
c. not grow on any minimal medium.
d. grow on a minimal medium but would not grow on a minimal medium with arginine.
e. None of the above

not grow on a minimal medium but would grow on a minimal medium with arginine.

Within a group of mutants with the same growth requirement (i.e., the same overt phenotype), mapping studies determined that individual mutations were on different chromosomes. This indicates that
a. the same gene governs all the steps in a particular biological pathway.
b. different genes can govern different individual steps in the same biological pathway.
c. different genes govern the same step in a particular biological pathway.
d. all biological pathways are governed by different genes.
e. genes do not govern steps in biological pathways.

different genes can govern different individual steps in the same biological pathway.

The study of Neurospora mutants grown on various supplemented media led to
a. a determination of the steps in biological pathways.
b. the "one-gene, one-enzyme" theory.
c. the idea that genes are "on" chromosomes.
d. Both a and b
e. Both a and c

Both a and b

Genes code for
a. enzymes.
b. polypeptides.
c. RNA.
d. All of the above
e. None of the above

All of the above

The classic work of Beadle and Tatum, later refined by others, provided evidence for the
a. one-gene, one-enzyme hypothesis.
b. one-gene, one-polypeptide hypothesis.
c. mechanism by which information in genes is translated into traits.
d. effects of some mutations on organisms.
e. All of the above

All of the above

How does RNA differ from DNA?
a. RNA contains uracil instead of thymine and it is usually single-stranded.
b. RNA contains uracil instead of thymine and it is usually double-stranded.
c. RNA contains thymine instead of uracil and it is usually single-stranded.
d. RNA contains uracil instead of cytosine.
e. None of the above

RNA contains uracil instead of thymine and it is usually single-stranded

Which of the following statements about the flow of genetic information is true?
a. Proteins encode information that is used to produce other proteins of the same amino acid sequence.
b. RNA encodes information that is translated into DNA, and DNA encodes information that is translated into proteins.
c. Proteins encode information that can be translated into RNA, and RNA encodes information that can be transcribed into DNA.
d. DNA encodes information that is translated into RNA, and RNA encodes information that is translated into proteins.
e. None of the above

DNA encodes information that is translated into RNA, and RNA encodes information that is translated into proteins

Which of the following molecules transfers information from the nucleus to the cytoplasm?
a. DNA
b. mRNA
c. tRNA
d. Proteins
e. Lipids

mRNA

The link between mRNA and a protein is
a. tRNA.
b. a promoter.
c. RNA polymerase.
d. DNA polymerase.
e. a start codon.

tRNA.

Which of the following molecules transfers information from mRNA to protein?
a. DNA
b. mRNA
c. tRNA
d. Proteins
e. Lipids

tRNA

The "central dogma" of molecular biology states that
a. information flow between DNA, RNA, and protein is reversible.
b. information flow in the cell is unidirectional, from protein to RNA to DNA.
c. information flow in the cell is unidirectional, from DNA to RNA to protein.
d. the DNA sequence of a gene can be predicted if we know the amino acid sequence of the protein it encodes.
e. the genetic code is ambiguous but not degenerate.

information flow in the cell is unidirectional, from DNA to RNA to protein.

The adapters that allow translation of the four-letter nucleic acid language into the 20-letter protein language are called
a. aminoacyl tRNA synthetases.
b. transfer RNAs.
c. ribosomal RNAs.
d. messenger RNAs.
e. ribosomes.

transfer RNAs.

Which of the following does (do) not follow the "central dogma"?
a. Yeast
b. Onion cells
c. Bread mold
d. Skin cells
e. Retroviruses

Retroviruses

Retroviruses do not follow the "central dogma" of DNARNAprotein because they
a. contain RNA that is used to make DNA.
b. contain DNA that is used to make more RNA.
c. contain DNA that is used to make tRNA.
d. contain only RNA as the genetic material.
e. do not contain either DNA or RNA as the genetic material.

contain RNA that is used to make DNA.

Viruses that violate the "central dogma" through the use of an enzyme that makes DNA copies of an RNA molecule are called
a. bacteriophage.
b. retroviruses.
c. RNA viruses.
d. DNA viruses.
e. enveloped viruses.

retroviruses.

Single-stranded RNA replicates by
a. making an RNA strand that is complementary to the original RNA strand.
b. using an adapter molecule.
c. the process of transcription.
d. the process of translation.
e. the process of reverse transcription.

making an RNA strand that is complementary to the original RNA strand.

Transcription is the process of
a. synthesizing a DNA molecule from an RNA template.
b. assembling ribonucleoside triphosphates into an RNA molecule without a template.
c. synthesizing an RNA molecule using a DNA template.
d. synthesizing a protein using information from a messenger RNA.
e. replicating a single-stranded DNA molecule.

synthesizing an RNA molecule using a DNA template.

The process of transcription synthesizes
a. transfer RNA.
b. messenger RNA.
c. ribosomal RNA.
d. proteins.
e. a, b, and c

a, b, and c

The region of DNA in prokaryotes to which RNA polymerase binds most tightly is the
a. promoter.
b. poly C center.
c. enhancer.
d. operator site.
e. minor groove.

promoter.

Promoters are made of
a. proteins.
b. carbohydrates.
c. lipids.
d. nucleic acids.
e. amino acids.

nucleic acids.

A transcription start signal is called a(n)
a. initiation codon.
b. promoter.
c. origin.
d. operator.
e. nonsense codon.

promoter.

RNA polymerase uses the _______ DNA template to synthesize a _______ mRNA.
a. 5' to 3'; 5' to 3'
b. 3' to 5'; 3' to 5'
c. 5' to 3'; 3' to 5'
d. 3' to 5'; 5' to 3'
e. Examples of all of the above have been found.

3' to 5'; 5' to 3'

RNA polymerase is a(n)
a. RNA-directed DNA polymerase.
b. RNA-directed RNA polymerase.
c. DNA-directed RNA polymerase.
d. typical enzyme.
e. form of RNA.

DNA-directed RNA polymerase.

The direction of synthesis for a new mRNA molecule is _______ from a _______ template strand.
a. 5' to 3'; 5' to 3'
b. 5' to 3'; 3' to 5'
c. 3' to 5'; 5' to 3'
d. 3' to 5'; 3' to 5'
e. 5' to 5'; 3' to 3'

5' to 3'; 3' to 5'

The error rate for RNA polymerase is _______ that for most DNA polymerases.
a. less than
b. equal to
c. greater than
d. greater for frame shifts but less for base substitutions than
e. greater for base substitutions but less for frame shifts than

greater than

The process of transcription requires
a. a temporary stopping of DNA replication.
b. a temporary separation of the strands in the DNA template.
c. destruction of one of the strands of the DNA template.
d. relaxation of positive supercoils in the DNA template.
e. induction of positive supercoils in the DNA template

a temporary separation of the strands in the DNA template.

DNA is composed of two strands, only one of which typically is used as a template for RNA synthesis. By what mechanism is the correct strand chosen?
a. Both strands are tried and the one that works is remembered.
b. Only one strand has the start codon.
c. The promoter acts to aim the RNA polymerase.
d. A start factor informs the system.
e. It is chosen randomly.

The promoter acts to aim the RNA polymerase

There are differences in the amount of transcription that takes place for different genes. One reason for these differences is that
a. some promoters are more effective at transcription initiation.
b. longer genes take longer to transcribe.
c. the outcome is influenced by random chance.
d. ribosomes tend to attach to transcripts even before transcription is completed.
e. None of the above

some promoters are more effective at transcription initiation.

. Termination of transcription involves a
a. stop codon.
b. terminator sequence.
c. termiproteator.
d. hairline slip.
e. series of As.

terminator sequence.

There are _______ different RNA polymerases in eukaryotes.
a. two
b. three
c. four
d. five
e. six

three

The termination of transcription is signaled by
a. the stop codon.
b. a sequence of nitrogenous bases.
c. a protein bound to a certain region of DNA.
d. rRNA.
e. tRNA.

a sequence of nitrogenous bases.

In eukaryotes, there are _________ RNA polymerases that catalyze the synthesis of RNA from DNA.
a. two
b. three
c. four
d. five
e. six

three

The stop codons code for
a. no amino acid.
b. methionine.
c. glycine.
d. halt enzyme.
e. DNA binding protein.

no amino acid.

How can DNA, which is made up of only four different bases, encode the information necessary to specify the workings of an entire organism?
a. DNA molecules are extremely long.
b. DNA molecules form codons of three bases that code for amino acids.
c. The genetic code is redundant but not ambiguous.
d. DNA can be replicated with low error rates.
e. All of the above

All of the above

How many codons specify amino acids?
a. 20
b. 23
c. 45
d. 60
e. 61

61

The genetic code is best described as
a. redundant but not ambiguous.
b. ambiguous but not redundant.
c. both ambiguous and redundant.
d. neither ambiguous nor redundant.
e. nonsense.

redundant but not ambiguous.

The three codons in the genetic code that do not specify amino acids are called
a. missense codons.
b. start codons.
c. stop codons.
d. promoters.
e. initiator codons.

stop codons.

A template DNA strand has the following base sequence: 3'-GUC, CCA-5'. What would be the corresponding mRNA sequence?
a. 3'-GUC, CCA-5'
b. 5'-GUC, CCA-5'
c. 3'-CAG, GGU-5'
d. 5'-CAG, GGU-3'
e. 5'-CAG, GGT-3'

. 5'-CAG, GGU-3'

Imagine that a novel life form is found deep within Earth's crust. Evaluation of its DNA yields no surprises. However, it is found that a codon for this life form is just two bases in length. How many different amino acids could this organism be composed of?
a. 4
b. 8
c. 16
d. 32
e. 64

16

. Poly uracil codes for
a. three different amino acids.
b. poly tryptophan.
c. mRNA.
d. a fatty acid.
e. phenylalanine.

phenylalanine.

What events must take place to ensure that the protein made is the one specified by mRNA?
a. tRNA must read mRNA correctly.
b. tRNA must carry the amino acid that is correct for its reading of the mRNA.
c. covalent bonding between the base pairs must occur.
d. Both a and b
e. All of the above

Both a and b

Fewer different tRNA molecules exist than might have been expected for the complexity of its function. This is possible because
a. the third position of the codon does not have to pair conventionally.
b. the second position of the codon does not have to pair conventionally.
c. the anticodon does not have the conventional bases.
d. there are fewer amino acids than there are possible codons.
e. the code is degenerating.

the third position of the codon does not have to pair conventionally.

A sequence of three RNA bases can function as a(n)
a. codon.
b. anticodon.
c. gene.
d. Both a and b
e. Both a and c

Both a and b

The difference between mRNA and tRNA is that
a. tRNA has a more elaborate three-dimensional structure.
b. tRNAs are usually much smaller than mRNAs.
c. mRNA carries amino acids.
d. Both a and b
e. None of the above

Both a and b

How is it possible for single-stranded RNA to fold into complex shapes?
a. Phosphodiester linkages form between the phosphate and the sugar ribose.
b. Internal base pairings make this possible: adenine with uracil and cytosine with guanine.
c. Uracil's methyl group binds to adenine, spiraling the molecule.
d. The single strand "twists" around itself.
e. The RNA binds to proteins, creating a conformation (three-dimensional shape).

Internal base pairings make this possible: adenine with uracil and cytosine with guanine.

Which of the following statements about codons and anticodons is true?
a. The codon bonds covalently with the anticodon.
b. The base sequences are the same.
c. There are 64 codons and 61 anticodons.
d. Activating enzymes link codons and anticodons.
e. At contact, the codon and the anticodon are anti¬parallel to each other.

At contact, the codon and the anticodon are anti¬parallel to each other.

The conformation of tRNA is maintained by
a. peptide bonds.
b. hydrogen bonds.
c. disulfide bridges.
d. phosphodiester bonds.
e. glycosidic linkages.

hydrogen bonds

Activating enzymes
a. are sometimes referred to as the second genetic code.
b. link the right tRNAs and amino acids.
c. are also known as aminoacyl-tRNA synthetases.
d. are specific for one amino acid.
e. All of the above

All of the above

The energy for translation is derived from
a. ATP.
b. GTP.
c. ATP and GTP.
d. the phosphodiester linkages in the incorporated nucleoside triphosphates.
e. glucose.

he phosphodiester linkages in the incorporated nucleoside triphosphates.

The enzyme that charges the tRNA molecules with appropriate amino acids is
a. tRNA chargeatase.
b. amino tRNA chargeatase.
c. transcriptase.
d. aminoacyl-tRNA synthetase.
e. None of the above

aminoacyl-tRNA synthetase.

Ribosomes are a collection of _______ that are needed for _______.
a. small proteins; translation
b. proteins and small RNAs; translation
c. proteins and tRNAs; transcription
d. proteins and mRNAs; translation
e. mRNAs and tRNAs; translation

proteins and small RNAs; translation

During translation initiation, the first site occupied by a charged tRNA is the
a. A site.
b. B site.
c. large subunit.
d. T site.
e. P site.

P site.

It is currently believed that the enzyme that catalyzes formation of the peptide bond during translation is composed of
a. amino acids.
b. proteins.
c. carbohydrates.
d. RNA.
e. DNA.

RNA.

During translation elongation, the existing polypeptide chain is transferred to
a. the tRNA occupying the A site.
b. the tRNA occupying the P site.
c. the ribosomal rRNA.
d. a signal recognition particle.
e. None of the above

the tRNA occupying the P site.

. mRNA is synthesized in the _______ direction, which corresponds to the _______ of the protein.
a. 5' to 3'; N terminus to C terminus
b. 3' to 5'; C terminus to N terminus
c. 5' to 3'; C terminus to N terminus
d. 3' to 5'; N terminus to C terminus
e. Examples of all of the above have been found.

5' to 3'; N terminus to C terminus

Proteins are synthesized from the _______, in the _______ direction along the mRNA.
a. N terminus to C terminus; 5' to 3'
b. C terminus to N terminus; 5' to 3'
c. C terminus to N terminus; 3' to 5'
d. N terminus to C terminus; 3' to 5'
e. N terminus to N terminus; 5' to 5'

N terminus to C terminus; 5' to 3'

. In protein synthesis, the endoplasmic reticulum
a. is the site where mRNA attaches.
b. is the site where all ribosomes bind.
c. is the site of translation of membrane-bound and exported proteins.
d. produces tRNAs.
e. brings together mRNA and tRNA.

is the site of translation of membrane-bound and exported proteins.

Which of the following is the correct order of events by which a protein is delivered to its cellular destination?
a. A signal sequence binds to a docking protein, a membrane channel is formed, chaperonins unfold the protein, the protein enters the organelle, and the protein refolds.
b. A membrane channel is formed, a signal sequence binds to a docking protein, chaperonins unfold the protein, the protein enters the organelle, and the protein refolds.
c. Chaperonins unfold the protein, a signal sequence binds to a docking protein, a membrane channel is formed, the protein enters the organelle, and the protein refolds.
d. A membrane channel is formed, chaperonins unfold the protein, a signal sequence binds to a docking protein, the protein enters the organelle, and the protein refolds.
e. A signal sequence binds to a docking protein, a transmembrane-gated channel opens, and the protein enters the organelle.

A signal sequence binds to a docking protein, a membrane channel is formed, chaperonins unfold the protein, the protein enters the organelle, and the protein refolds.

In eukaryotes, ribosomes become associated with endoplasmic reticulum membranes when
a. a signal sequence on the mRNA interacts with a receptor protein on the membrane.
b. a signal sequence on the ribosome interacts with a receptor protein on the membrane.
c. a signal sequence at the amino terminus of the protein being synthesized interacts with a receptor protein on the ribosome.
d. a signal sequence on the protein being synthesized interacts with a signal recognition particle and both bind to the endoplasmic reticulum.
e. the messenger RNA passes through a pore in the membrane.

a signal sequence on the protein being synthesized interacts with a signal recognition particle and both bind to the endoplasmic reticulum

The addition of sugar residues to the protein after translation is called
a. glycation.
b. glycosylation.
c. phosphorylation.
d. proteolysis.
e. exonuclease digestion.

glycosylation.

After translation, some proteins are processed by _______, which is cleavage of the protein to make a shortened finished protein.
a. glycation
b. glycosylation
c. phosphorylation
d. proteolysis
e. exonuclease digestion

proteolysis

In eukaryotic cells, proteins that contain covalently attached sugar residues are translated
a. in the nucleus.
b. in the cytoplasm.
c. in mitochondria.
d. on the endoplasmic reticulum.
e. on the Golgi apparatus.

on the endoplasmic reticulum

Mutations are
a. heritable changes in the sequence of DNA bases that produce an observable phenotype.
b. heritable changes in the sequence of DNA bases.
c. mistakes in the incorporation of amino acids into proteins.
d. heritable changes in the mRNA of an organism.
e. None of the above

heritable changes in the sequence of DNA bases.

The type of mutation that stops translation of a protein is a(n)
a. missense mutation.
b. nonsense mutation.
c. frame-shift mutation.
d. aberration.
e. None of the above

nonsense mutation

The type of mutation that is an insertion or a deletion of a single base is a(n)
a. missense mutation.
b. nonsense mutation.
c. frame-shift mutation.
d. aberration.
e. None of the above

frame-shift mutation.

. Sickle-cell disease is caused by a _______ mutation.
a. nonsense
b. missense
c. frame-shift
d. temperature sensitive
e. silent

missense

Breaking and rejoining of chromosomes can lead to
a. deletions.
b. duplications.
c. inversions.
d. translocations.
e. All of the above

All of the above

Damage to DNA can be caused by _______ absorbed by thymine in DNA, causing interbase covalent bonds.
a. X-rays
b. cosmic radiation
c. ultraviolet radiation
d. smoke
e. cigarettes

ultraviolet radiation

The rates of DNA mutations are _______ in different organisms.
a. the same
b. constant
c. different
d. dependent on health
e. dependent on temperature

different

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