Bio Unit 3

Suppose X-rays caused a sequence change in the TATA box of a particular gene’s promoter? How would that affect the transcription of the gene?

a. transcription would increase b/c the RNA polymerase would bind more strongly

b. Transcription would decrease or fail b/c RNA polymerase and transcription factors might not bind properly

c. The gene would be transcribed normally b/c the TATA box is not important for transcription

d. Transcription would start at multiple random sites instead of the correct start site

b

Unripe black walnuts contain a compound called juglone that blocks the action of RNA polymerase. Which cellular process would be most directly affected by juglone?

a. mutation rate

b. DNA replication

c. transcription

d. translation 

c

The template strand of a portion of a gene reads 5’TCATTGCAA3’. What will be the sequence of the mRNA resulting transcript for this portion?

a. 3’AGUAACGUU5’

b. 3’AGTAACGTT5’

c. 3’TCATTGCAA5’

d. 3’UUGCAAUGA5’

a

A geneticist isolates a gene for a specific trait under study. She also isolates the corresponding mRNA. Upon comparison, the mRNA is found to contain 1000 fewer bases than the DNA sequence. Did the geneticist isolate the wrong DNA?

a. yes, mRNA is made from a DNA template and should be the same length as the gene sequence 

b. yes, the mRNA should contain more bases than the DNA sequence because bases flanking the gene are also transcribed

c. no, the final mRNA contains only exons, the introns were removed 

d. no, the mRNA was partially degraded after it was transcribed 

c

What would be the effect of treating cells with an agent that removed 5’ cap from mRNA?

a. mRNA will not leave the nucleus

b. mRNA will not be spliced

c. mRNA will not be able to attach to ribosomes

d. mRNA will be easily degraded in cytoplasm

a, c, d

Which of the following terms describes the DNA-protein complexes the look like beads on a string?

a. 30-nanometer fiber

b. chromatin

c. nucleosome

d. histones

c

Which of the following regulatory elements is not composed of DNA sequences?

a. silencers

b. promoter-proximal elements

c. activators

d. enhancers

c

Ture or false? Regulatory and basal transcription factors regulate transcription by binding to the promoter?

a. true

b. false

b

Which of the following regulatory DNA sequences might be located thousands of nucleotides away from the transcription start site of a gene?

a. promoter-proximal element

b. enhancer

c. TATA box

d. promoter 

b

Which of the following events in transcription initiation likely occurs last?

a. basal transcription factors form a basal transcription complex

b. RNA polymerase binds to the promoter of the gene

c. regulatory transcription factors bind to enhancers

d. TBP is recruited to the promoter

b

True or false? One possible way to alter chromatin structure such that genes could be transcribed would be to make histone proteins positively charged.

a. true

b. false

b

DNA methylation is a mechanism used by eukaryotes to

a. cause apoptosis

b. inactivate genes

c. terminate transcription

d. facilitate the binding of DNA to intermediate filaments

e. increase the rate of transcription

b

Which of the following chemical modifications leads to condensation of chromatin and therefore reduces levels of transcription?

a. histone methylation, DNA methylation, and histone acetylation

b. histone methylation and DNA methylation

c. DNA methylation

d. histone acetylation

e. histone methylation 

b

Enzyme complexes that break down protein are called

a. lipases

b. ubiquitins

c. amylase

d. proteasomes

e. nucleases

d

The nuclear membrane’s role in the regulation of gene expression involves

a. protein activation

b. translation

c. protein degradation

d. regulating the transport of mRNA to the cytplasm

e. RNA processing 

d

What is the function of spliceosome?

a. protein activation

b. translation

c. protein degradation

d. regulating the transport of mRNA to the cytoplasm 

e. RNA processing 

e

Protein-phosphorylating enzymes’ role in the regulation of gene expression involves

a. protein activation

b. translation

c. protein degradation

d. regulating the transport of mRNA to the cytoplasm

e. RNA processing

a

In humans, the steroid hormone testosterone enters cells and binds to specific proteins, which in turn bind to specific sites on the cells’ DNA. The result is expression of genes associated with male sexual characteristics. What is the function of these proteins?

a. to alter the pattern of DNA splicing 

b. to promote recombination

c. to methylate the DNA so that its genes can be transcribed

d. to help RNA polymerase transcribe certain genes 

e. to cause mutations in the DNA 

d

It is possible for a cell to make proteins that last for months; hemoglobin in red blood cells is a good example. However, many proteins are not this long-lasting; they may be degraded in days, hours, or even minutes. What is the advantage of short-lived proteins?

a. most cells have a short life span

b. short-lived proteins enable the cells to control their activities precisely and efficiently

c. long-lasting proteins are likely to make the cell cancerous

d. cells lack the raw materials to make most of the proteins they need

e. most proteins are used only once

b

If the 5’ to 3’ nucleotide sequence on the nontemplate DNA strand is CAT, what is the corresponding codon on mRNA?

a. CAU

b. UAC

c. GUA

d. GTA

e. CAT

a

The type of mutation responsible for sickle-cell anemia is

a. both a point mutation and a nucleotide-pair substitution 

b. a silent mutation

c. a nucleotide-pair insertion

d. a point mutation

e. a nucleotide-pair substitution 

a

Which of the following is not a post-translational modification that might be required of a protein before it becomes functional in a cell?

a. attachment of sugars to amino acids of the protein 

b. all of the listed responses 

c. removal of an amino acid

d. cleavage of a polypeptide chain 

e. binding of two or more polypeptide chains 

b

Which of the following is not transcribed from DNA?

a. exons

b. introns

c. promoter

d. tRNA

e. 3’ and 5’ UTRs

c

Which of the following is not part of the translation initiation complex?

a. mRNA

b. TATA box

c. initiator tRNA 

d. small ribosomal unit

e. large ribosomal unit 

b

A series of studies on mutants of Neurospora identified three classes of mutants that needed arginine added to minimal media in order to grow. The production of arginine includes the following steps: precursor —> ornithine —>citrulline —> arginine. What nutrients have to be supplied to the mutants that had a defective enzyme for the orthinie-citrulline step in order to grow?

a. citrulline

b. the precursor

c. ornithine

d. either ornithine or citrulline

e. the precursor, ornithine, and citrulline 

a

How is the template strand for a particular gene determined?

a. it is established by the presence of the promoter

b. it is the DNA strand that runs from the 5’ to 3’ direction 

c. it is the DNA strand that runs from the 3’ to 5’ direction 

d. it doesn’t matter which strand is the template because they are complementary and will produce the same mRNA 

e. it is signaled by the polyadenylation signal sequence 

a

A nucleotide deletion early in the coding sequence of a gene would most likely result in 

a. a frameshift mutation

b. a nonsense mutation

c. multiple missense mutations

d. all of the listed choices

e. a nonfunctional protein 

d

RNA polymerase

a. is the molecule of which ribosomes are constructed 

b. is the enzyme that catalyzes the joining of each amino acid to the right tRNA 

c. is the enzyme that transcribes exons but does not transcribe introns

d. moves along the template strand of DNA, elongating an RNA molecule in a 5’ to 3’ direction

e. is a ribozyme 

d

A signal peptide

a. is the first 20 or so amino acids of a protein destined for a membrane location or for secretion from the cell

b. is most likely to be found on cytosolic proteins produced by bacterial cells 

c. directs an mRNA molecule into the lumen of the ER

d. is a sign to bind the small ribosomal unit at the initiation codon

e. is part of the UTR following the 5’ cap 

a

Which binding site on a ribosome holds a tRNA attached to a growing polypeptide chain?

a. A site

b. P site

c. E site

d. the P site, A site, and E sites all hold tRNA attached to polypeptides

e. none of the responses 

b

Which of the following is transcribed and then translated to form a protein product?

a. a gene for tRNA

b. an intron

c. a gene for a transcription factor

d. 5’ to 3’ UTRs

e. a gene for rRNA 

c

A stretch of bacterial DNA 600 nucleotides long can code at most for a polypeptide of how many amino acids?

a. 100

b. 300

c. 200

d. 600

e. 1800

c

Which of the following is true of transcription factors?

a. all of the listed responses

b. transcription factors are present in eukaryotic cell nuclei

c. transcription factors are produced in a cell as a result of both gene transcription and translation

d. transcription factors are proteins

e. transcription factors bind to promoters

a

Which enzyme synthesizes tRNA?

a. DNA polymerase

b. RNA polymerase

c. reverse transcriptase

d. aminoacyl-tRNA synthetase

e. ribosomal RNA 

b

Transcription involves the transfer of information from

a. RNA to DNA

b. mRNA to an amino acid sequence

c. DNA to an amino acid sequence

d. DNA to RNA

e. the nucleus to the cytoplasm

d

Which of the following is a stop codon?

a. UGA

b. CAU

c. CAC

d. AAG

e. AUG 

a

What is the name of the process in which DNA is used as a template for pre-mRNA?

a. RNA processing

b. gene expression

c. polypeptide formation

d. transcription 

e. translation 

d

What name is given to the process in which the information encoded in a strand of mRNA is used to construct a protein?

a. RNA processing

b. gene expression

c. polypeptide formation

d. transcription

e. translation 

e

What name is given to the process in which pre-mRNA is edited into mRNA?

a. RNA processing

b. gene expression

c. polypeptide formation

d. transcription

e. translation

a

Polypeptides are assembled from

a. hexoses

b. glycerol

c. nucleotides

d. proteins

e. amino acids 

e

RNA processing converts the RNA transcript into

a. a protein

b. DNA

c. a eukaryotic cell

d. mRNA

e. a polypeptide 

d

What is the function of RNA polymerase?

a. it proceeds slowly along the DNA strand, requiring about a minute to add two nucleotides to the growing mRNA molecule

b. it relies on other enzymes to unwind the double helix

c. all of the listed responses are correct

d. it unwinds the double helix and adds nucleotides to a growing strand of RNA

e. it adds nucleotides to the 5’ end of the growing mRNA molecule 

d

Where does RNA polymerase begin transcribing a gene into mRNA?

a. it starts at one end of the chromosome 

b. it looks for the AUG codon 

c. transfer RNA acts to translate the message to RNA polymerase

d. it starts after a certain nucleotide sequence called a promoter

e. the ribosome directs it to the correct portion of the DNA molecule 

d

What is the process called that converts DNA to RNA?

a. translation

b. replication

c. transcription

d. translocation

c

DNA does not store the information to synthesize which of the following?

a. DNA

b. mRNA
c. organelles

d. proteins

c

Transcription begins at a promoter. What is a promoter?

a. a site found on the RNA polymerase

b. the same as a start codon

c. a site in DNA that recruits the RNA polymerase

d. part of the RNA molecule itself 

c

Which of the following statements best describes the promoter of a protein-coding gene?

a. the promoter is a notrasncibred region of a gene

b. the promoter is a site found on RNA polymerase

c. the promoter is a site at which only RNA polymerase will bind

d. the promoter is part of the RNA molecule itself

a

What determines which base is to be added to an RNA strand during transcription?

a. base pairing between the DNA template strand and the RNA nucleotides

b. the previous base

c. the order of the chemical groups in the backbone of the RNA molecule 

d. base pairing between the two DNA strands

a

Which of the following terms best describes the relationship between the newly synthesized RNA molecule and the DNA template strand?

a. permanently base-paired

b. complementary

c. identical

d. covalently bound 

b

What happens to RNA polymerase II after it has completed transcription of a gene?

a. it is degraded

b. it joins with another RNA polymerase to carry out transcription

c. it begins transcribing the next gene on the chromosome

d. it is free to bind to another promoter and begin transcription 

d

After an RNA molecule is transcribed from a eukaryotic gene, what is removed and what is spliced together to produce an mRNA molecule with a continuous coding sequence?

a. promoters .. operators

b. exons .. introns

c. silencers … enhancers

d. operators .. promoters

e. introns .. exons

e

What is a ribozyme?

a. an enzyme that holds open the DNA double helix while RNA polymerase adds nucleotides

b. a DNA sequence near the promoter that assists in the binding of RNA polymerase

c. a biological catalyst made of RNA 

d. a biological catalyst consisting of DNA 

e. a mutated ribosome 

c

During RNA processing a ___ is added to the 5’ end of the RNA

a. a 3’ untranslated region

b. a long string of adenine nucleotides 

c. 5’ untranslated region

d. coding segment 

e. modified guanine nucleotide

e

During RNA processing a __ is added to the 3’ end of RNA

a. 3’ untranslated region

b. a long string of adenine nucleotides

c. 5’ untranslated region

d. coding segment

e. modified guanine nucleotide

b

Spliceosomes are composed of

a. small RNAs and proteins

b. polymerases and ligases

c. introns and exons

d. the RNA transcript and protein 

a

The RNA segments joined to one another by spliceosomes are

a. caps

b. exons

c. snRNPs

d. tails

e. introns

b

Translation occurs in

a. cytoplasm

b. lysosome

c. nucleus

d. golgi apparatus

e. nucleoplasm

a

The anticodon of a particular tRNA molecule is

a. catalytic, making the tRNA a ribozyme

b. the part of tRNA that bonds with a specific amino acid

c. complementary to the corresponding mRNA codon 

d. complementary to the corresponding triplet in rRNA

c

Which one of the following is true of tRNAs?

a. all of the above

b. there are 4 types of tRNA 

c. tRNAs carry special sequences known as codons

d. tRNAs carry amino acids to the ribosome during translation 

e. tRNAs are double-stranded 

d

Where does translation take place?

a. golgi

b. ribosome

c. nucleus

d. ER

b

Which nucleic acid is translated to make a protein?

a. mRNA 

b. tRNA

c. DNA

d. rRNA 

a

Which of the following processes is an example of a post-translational modification?

a. elongation

b. initiation

c. peptide bond formation

d. phosphorylation 

d

Which of the following steps occurs last in the initiation phase of translation?

a. the large ribosomal subunit joins the complex

b. an aminoacyl tRNA binds to the start codon 

c. the small subunit of the ribosome binds to the 5’ cap on the mRNA 

d. a peptide bond is formed between two adjacent amino acids

a

At which site do new aminoacyl tRNAs enter the ribosome during elongation?

a. B-site

b. P-site

c.  A-site

d. E-site

c

What is meant by translocation?

a. the ribosome slides one codon down the mRNA

b. the polypeptide chain grows by one amino acid

c. the two ribosomal subunits are joined in a complex

d. the completed polypeptide is released from the ribosome 

a

True or false? A tRNA with an anticodon complementary to the stop codon catalyzes the reaction by which translation is terminated

a. true

b. false 

b

What is the direct result of a mutagen?

a. problems with mitosis

b. decreased permeability of the nuclear envelope

c. a reduction in the number of tRNA molecules available for protein synthesis 

d. decreased enzyme activity throughout the cell 

e. a change in the sequence of DNA 

e

DNA polymerase adds nucleotides to the of the leading strands and to the_ of the lagging strands

a. 3’ end, 3’ end 

b. 5’ end, 3’ end

c. 3’ end, 5’ end 

d. 5’ end, 5’ end 

a

A scientist assembles a bacteriophage with the protein coat of T2 and the DNA of phage T4. If this composite phage were allowed to infect a bacterium, the phages produced in the host cell would have 

a. the protein and DNA of T4

b. the protein of T2 and the DNA of T4

c. the protein of T4 and the DNA of T2

d. a mixture of the DNA and proteins of both phages

e. the protein and DNA of T2

a

Which of the following components is required for DNA replication?

a. ribosomes

b. RNA primers

c. tRNA

d. proteases

e. sucrases 

b

What technique was most helpful to Watson and Crick in developing their model for the structure of DNA?

a. gel electrophoresis 

b. cloned DNA

c. transgenic animals

d. x-ray crystallography 

e. radioactive labeling 

d

Which of the following statements concerning the structure of DNA is correct?

a. adenine forms two hydrogen bonds with guanine; thymine forms three hydrogen bonds with cytosine

b. A from 3 H bonds with T, G forms 2 H bonds with C 

c. A forms 2 covalent bonds with T, G forms 3 covalent bonds with C

d. A forms 3 covalent bonds with T, G forms 2 covalent bonds with C

e. A forms 2 H bonds with T, G forms 3 H bonds with C

e

What enzyme joins Okazaki fragments?

a. DNA ligase

b. nuclease

c. topoisomerase

d. helicase

e. primase

a

One strand of a double-stranded DNA molecules has the sequence 5’-ATAGGT-3’. The complementary base sequence on the other strand of DNA will be 3’ -____-5’

a.UAUCCA

b. ATAGGT

c. TATCCA

d. TGGATA

e. TGGAUA

c

Once the DNA at the replication fork is unwound by helicases, what prevents the two strands from coming back together to re-form a double helix?

a. one of the strands is rapidly degraded, preventing the double helix from re-forming

b. single-strand binding proteins bind the unwound DNA and prevent the double helix from re-forming 

c. the helicase modifies the DNA in such a way as to eliminate the affinity between the two strands

d. DNA polymerase follows the helicase so closely that there is no chance for the strands to come back together

e. the helicase pushes the two strands so far apart that they have no chance of finding each other 

b

Which of the following statements about origins of replication is correct?

a. all off the listed responses

b. bacterial chromosomes have a single origin, nut eukaryotic chromosomes have many origins

c. in bacteria, the DNA sequence at the origin is recognized by specific proteins that then bind to the origin 

d. the two strands of DNA at the origin are separated, allowing the formation of a replication bubble 

e. in both prokaryotes and eukaryotes, replication proceeds in both directions from each origin 

a

The beads on a string seen in interphase chromatin are

a. looped domains

b. heterochromatin

c. histone tails

d. nucleoids

e. nucleosomes

e

The unwinding of DNA at the replication fork causes twisting and strain in the DNA ahead of the fork, which is relieved by an enzyme called

a. ligase

b. helicase

c. nuclease

d. topoisomerase

e. priamse 

d

The role of DNA polymerase in DNA replication is to

a. attach free nucleotides to the new DNA strand

b. synthesize a RNA primer to initiate DNA strand syntehsis 

c. link together short strands of DNA

d. separate the two strands of DNA

e. all of the responses

a

The incorporation of an incorrect base into a DNA molecule during replication

a. will almost certainly lead to the death of the cell

b. can be repaired by the mismatch repair system 

c. will catalyze additional mutations

d. ends replication of the molecule

e. is virtually impossible, as the accuracy of DNA polymerase is such that errors almost never occur 

b

What are chromosomes made of?

a. DNA

b. DNA, heterochromatin, and histone proteins

c. DNA and euchromatin

d. DNA and proteins

e. DNA, RNA, and proteins

d

Enzymes that break down DNA catalyze the hydrolysis of the covalent bonds that join nucleotides together. What would happen to DNA molecules treated with these enzymes?

a. all bases would be separated from the deoxyribose sugars

b. the pyrimidines would be separated from the deoxyribose sugars

c. the two strands of the double helix would separate

d. the phosphodiester linkages of the polynucleotide backbone would be broken

d

If one strand of a DNA molecule has the sequence of bases 5’-ATTGCA-3’, the other complementary strand would have the sequence

a. 3’-UAACGU-5’

b. 5’-UAACGU-3’

c. 5’-TAACGT-3’

d. 5’-TGCAAT-3’

d

What is the role of DNA polymerase during DNA synthesis?

a. catalyzes the synthesis of the template strand of DNA

b. is the enzyme that catalyzes the addition of a nucleotide onto the 3’ end of a growing DNA strand

c. removes inorganic phosphate from the template strand of DNA to catalyze the polymerization reaction 

d. provides the free energy to catalyze the endergonic addition of a nucleotide onto the 3’ end of a growing DNA strand

b

What are the repetitive DNA sequences present at the ends of eukaryotic chromosomes called?

a. chromomeres

b. polypeptides

c. telomeres

d. sarcomeres

e. centromeres 

c

What process repairs damage to preexisting double helix?

a. proofreading

b. nucleotide excision repair

c. mismatch repair

d. operon repair

e. transformtion

b

Short segments of newly synthesized DNA are joined into a continuous strand by 

a. single-strand binding protein 

b. primase

c. helicase

d. ligase

e. DNA polymerase 

d

The first step in the replication of DNA is catalyzed by 

a. helicase

b. ligase

c. primase

d. single-strand binding protein 

e. DNA polymerase 

a

The action of helicase creates

a. primers and replication bubbles

b. primers and DNA fragments

c. DNA fragments and replication bubbles

d. replication forks and replication bubbles

e. DNA fragments and replication forks 

d

Why is the new DNA strand complementary to the 3’ to 5’ strands assembled in short fragments?

a. DNA polymerase can assemble DNA only in the 5’ to 3’ direction 

b. DNA polymerase can assemble DNA only in the 3’ to 5’ direction

c. only short DNA sequences can extend off the RNA primers

d. it is more efficient than assembling complete new strands 

a

The synthesis of a new strand begins with the synthesis of a

a. okazaki fragment

b. RNA primer complementary to a pre-existing DNA strand

c. poly A tail

d. single-strand binding protein 

e. short pieces of DNA

b

Which of the following statements best describes the eukaryotic chromosome?

a. the number of genes on each chromosome is different in different cell types of an organism 

b. it is composed of DNA alone

c. it consists of a single linear molecule of double-stranded DNA plus proteins

d. the nucleosome is its most basic functional subunit 

c

If a cell were unable to produce histone proteins, which of the following effects would likely occur?

a. the cell’s DNA couldn’t be packed into its nucleus

b. DNA polymerase I would not function properly

c. expression of other genes would compensate for the lack of histones

d. spindle fibers would not form during prophase 

a

Which of the following statements correctly describes one characteristic of histones?

a. histones are found in mammals but not in other eukaryotes

b. each nucleosome consists of two histones

c. each nucleosome consists of eight histones

d. the carboxyl end of each histone extends outward from the nucleosome and is called a histone tail 

c

Why do histones bind tightly to DNA?

a. histones are positively charged, and DNA is negatively charged

b. histones are negatively charged, and DNA is positively charged 

c. both histones and DNA are strongly hydrophobic 

d. histones are covalently linked to the DNA 

a