Molecular Genetics Exam 2 Flashcards by Aleksandra Grigoryants

**The core octamer of a nucleosome is composed of
**

one each of 8 different types of histones

two tetramers of histones H3 and H4

a tetramer of histones H3 and H4, and two dimers of histones H2A and H2B

the linker histone H1

a tetramer of histones H3 and H4, and two dimers of histones H2A and H2B

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The site of many post-translational modification of the histone proteins is the

charged tails at the N-terminal end

conserved wing helix folds

charged tails at the C-terminal end

extended histone-fold domain at the C-terminal end

charged tails at the N-terminal end

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Brief digestion of eukaryotic chromatin with micrococcal nuclease gives a visible ladder of bands on an agarose gel separated from each other by multiples of ~180 bp. The fragment size represents

the different histone proteins

multiples of single nucleosomal repeat lengths of DNA

DNA that was wrapped around the core histone octamer

linker DNA

multiples of single nucleosomal repeat lengths of DNA

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The location of the centromere within a chromosome is determined by

the presence of the histone variant CENP-A.

the presence of linker histone.

the presence of an evolutionarily conserved centromere-determining sequence.

the point of equidistance between the two chromosome ends.

the presence of the histone variant CENP-A.

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Heterochromatin is

condensed, transcriptionally active chromatin.

decondensed, transcriptionally silent chromatin.

condensed, transcriptionally silent chromatin.

decondensed, transcriptionally active chromatin.

condensed, transcriptionally silent chromatin.

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Which of the following occupies the largest portion of the human genome?

introns

intergenic DNA

protein-coding sequences

gene regulatory sequences

intergenic DNA

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Condensation of chromatin requires ATP-hydrolyzing enzymes and to loop DNA and achieve a 10,000 fold packing ratio.

the kinetochore complex

the Ki-67 proteins

the condensin complex

the cohesin complex

the condensin complex

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**What statement is not true about plasmid DNA?
**
Plasmid DNA is self-replicating

Most plasmids are small, double-stranded circles.

Plasmid DNA is only found in bacteria

Plasmid DNA is extrachromosomal

Plasmid DNA is only found in bacteria

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**Which of the following is true of bacteriophage DNA packaging?
**

Bacteriophages take their host cell’s histone proteins to package their DNA

Bacteriophages usually have a lot of proteins associated with their DNA, helping to package it

Bacteriophages must pack their genome into a nucleus

Bacteriophages must pack their genome into a capsid

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Histone proteins are the main architectural proteins found in bacteria.

True
False

False

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Mitochondria contain DNA that encodes proteins important for oxidative phosphorylation.

True
False

True

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**Which of the following statements is correct?
**

DNA polymerase can start synthesis de novo.

There are five types of DNA polymerase in mammalian cells.

DNA polymerase catalyzes the formation of a phosphodiester bond between the first 3′hydroxyl group of the new dNTP and the 5′-phosphate of the last nucleotide in the newly synthesized strand.

DNA polymerase requires a primer to get started.

There is only one type of DNA polymerase in bacterial cells.

DNA polymerase requires a primer to get started.

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Which of the following is NOT TRUE with regards to DNA replication?

DNA replication initiation begins at a negatively supercoiled origin of replication

DNA replication is semiconservative

The origin of replication is rich in A and T nucleotides.

DNA replication in bacteria is normally bidirectional

DNA replication on the lagging strand is continuous

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Which of the following is an enzyme that would be found in Escherichia coli but not in humans?

DNA pol I

PCNA

Mcm2-7

RFC

DNA pol alpha

DNA pol I

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What protein or protein complex binds to the origin of replication in E. coli cells to initiate DNA replication?

ORC

Mcm2-7

DnaA

Topoisomerase II

Helicase

DnaA

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When does DNA replication occur in a eukaryotic cell?

G2 phase

G1 phase

M phase

S phase

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Which statement is NOT correct?

Eukaryotic chromosomal DNA replication occurs after replication licensing

Eukaryotic chromosomal DNA typically has only one origin of replication

Mammalian origins of replication do not have a consensus sequence

An origin of replication is a site on chromosomal DNA where a bidirectional pair of replication forks initiates.

Eukaryotic chromosomal DNA typically has only one origin of replication

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Which enzyme is responsible for sealing the DNA backbone following primer removal?

Restriction endonuclease

DNA ligase

Helicase

RNA polymerase

DNA gyrase

DNA ligase

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Which enzyme causes a double-strand DNA break while functioning?

RPA

Topoisomerase I

Klenow fragment

Topoisomerase II

DNA helicase

Clamp loader

Topoisomerase II

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Select all of the following that describe DNA transactions during replication.

The main enzyme for replication is DNA polymerase

It is semidiscontinuous

It does not have a specific beginning

It is bidirectional with 2 replication forks

It is conservative

The main enzyme for replication is DNA polymerase

It is semidiscontinuous

It is bidirectional with 2 replication forks

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An induced mutation occurs

spontaneously

as a result of interaction of DNA with an outside agent

as a result of natural processes in cells

as a result of DNA replication errors

as a result of interaction of DNA with an outside agent

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The most frequent UV light-induced DNA damage is

oxidation of guanine to 8-oxoguanine

double-strand breaks

induction of 5-bromouracil

forming a thymine dimer

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Which of the following is an intercalating agent?

5-bromouracil

8-Oxoguanine

Ethidium bromide

Nitrosamine

Ethidium bromide

Intercalacting agent: compounds that insert themselves between DNA base pairs and damage the DNA

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Removal of DNA-protein cross-links will most likely occur using which of the following enzymes?

methyltransferase

SPRTN protease

DNA polymerase IV

DNA photolyase

SPRTN protease

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**Which repair pathway would probably be involved in specifically recognizing and removing uracil (and other modified bases) from DNA?** non-homologous end joining homologous recombination nucleotide excision repair base excision repair

base excision repair

**The XP proteins are important for which type of repair?** direct repair non-homologous end-joining nucleotide excision base excision

nucleotide excision

**DNA repair mechanisms exhibit a recurrent theme. Which of the following describes this theme accurately?** A ribosome recognizes the damage, a RNA polymerase translates the DNA sequence, and a DNA polymerase connects double stranded DNA A polymerase removes DNA damage, a nuclease adds in the correct nucleotides, and a ligase seals double stranded DNA breaks A nuclease cuts out the damage, a polymerase adds in the correct nucleotides, a ligase fills in the nick in the backbone. A methyltransferase recognizes DNA damage, a glycosylase cuts the damage out, and a photolyase adds in the correct nucleotides

A nuclease cuts out the damage, a polymerase adds in the correct nucleotides, a ligase fills in the nick in the backbone.

**Which type of repair uses DNA glycosylases?** base excision nucleotide excision non-homologous end-joining direct repair

base excision

**The DNA repair system that removes replication errors and requires Mut proteins is ** Potoreactivation Nucleotide excision repair Mismatch repair Translesion DNA synthesis

Mismatch repair

Xeroderma pigmentosum may be caused by mutation in the gene that encodes DNA polymerase eta (η). True False

True

DNA polymerase eta (η) repairs DNA damage. True False

False

**Transcription is defined as the production of a(n): ** exact complementary strand of RNA from a DNA template. exact complementary strand of DNA from a RNA template. strand of DNA with a sequence identical to the RNA template. strand of RNA with a sequence identical to the DNA template. exact complementary strand of RNA from a RNA template.

exact complementary strand of RNA from a DNA template.

**Transcription begins at a _sequence encoded by the DNA when ___ recognizes the sequence. ** origin; DNA polymerase start codon; ribosome origin; RNA polymerase promoter; RNA polymerase promoter; DNA polymerase

promoter; RNA polymerase

**What is the CORRECT order of transcriptional events that occurs during initiation? ** Open complex formation, closed complex formation, abortive RNA synthesis, promoter clearance. Abortive RNA synthesis, open complex formation, closed complex formation, promoter clearance. Open complex formation, closed complex formation, promoter clearance, abortive RNA synthesis. Closed complex formation, open complex formation, abortive RNA synthesis, promoter clearance. Closed complex formation, open complex formation, promoter clearance, abortive RNA synthesis

Closed complex formation, open complex formation, abortive RNA synthesis, promoter clearance.

**Which of the following sigma factors is essential for general transcription in exponentially growing E. coli cells?** 54 38 70 28 32

**Which of the following does NOT contribute to the efficiency with which E. coli RNA polymerase binds to a promoter?** The sequence at the +10 region. The sequence of the upstream promoter element. The sequence at the -35 region. The binding of a sigma subunit.

The sequence at the +10 region.

**Transcription terminates in E. coli when** the -35 consensus sequence is reached termination sequences are reached leading to RNA hairpins pyrophosphorolysis occurs proofreading has been completed

termination sequences are reached leading to RNA hairpins *leads to RNA polymerase dissociation

**In E. coli, what is the function of the lac operon? ** It ensures that a cell dedicates resources to the production of enzymes involved in lactose metabolism only when lactose is available in the environment. It ensures that bacterial cells produce lactose only when no other food sources are available. It prevents other sugars from being metabolized until all available lactose has been used. It ensures that a cell produces enzymes involved in lactose metabolism in a constitutive manner.

It ensures that a cell dedicates resources to the production of enzymes involved in lactose metabolism only when lactose is available in the environment.

**In E.coli, what is the most likely thing to happen with the tryptophan operon when there are high levels of tryptophan? ** tryptophan is inactivating the repressor protein ribosomes are stalling during translation of the attenuator region the tryptophan operon will continue to be transcribed at relatively high levels transcription termination is likely

transcription termination is likely

**Which mode of action of a transcriptional regulator is exhibited by allolactose binding to the Lac repressor protein?** DNA looping DNA binding allosteric modification cooperative binding

allosteric modification, reduces its affinity for DNA

Transcription and translation are coupled in bacteria. True False

true, no nuclear membrane to separate the process

Bacteria generally have introns that must be removed from a primary transcript. True False

False, bacteria do not have introns and splicingin uncommon

Which of the following is NOT a histone protein that makes up the core octomer? A. H1 B. H2a C. H2b D. H3 E. H4

Heterochromatin is A. condensed, transcriptionally active chromatin. B. condensed, transcriptionally silent chromatin. C. decondensed, transcriptionally active chromatin. D. decondensed, transcriptionally silent chromatin

B. condensed, transcriptionally silent chromatin.

Which protein coats chromosomes to prevent them from sticking together during mitosis? A. Condensin B. Cohesin C. Ki-67 D. Kinetochore

C. Ki-67

DNA organization in eukaryotic cells does NOT include A. 10nm fiber B. 20nm fiber C. 30nm fiber D. Loop domains

B. 20nm fiber

The transfer of genetic material between the nucleus and mitochondria is A. Impossible B. Called Vertical Gene Transfer C. Called Lateral Gene Transfer D. Called Rolling Circle Gene Transfer E. Occurring constantly

C. Called Lateral Gene Transfer

Phosphodiester bonds are formed, connecting the backbones of adjacent Okazaki fragments, by A. DNA polymerase B. topoisomerase C. DNA ligase I D. telomerase

C. DNA ligase I

Positive supercoils ahead of the replication fork are resolved by cutting both strands of DNA and unwinding the DNA using A. helicase B. DNA polymerase/primase C. PCNA, the sliding clamp D. Topoisomerase I E. Topoisomerase II

E. Topoisomerase II

Replication licensing ensures that A. DNA replication occurs by a semiconservative mechanism. B. DNA only replicates once per cell cycle. C. only one origin of replication is active within a cell at a time. D. DNA replication only occurs during the G2 phase of the cell cycle

B. DNA only replicates once per cell cycle.

DNA polymerase delta and DNA polymerase epsilon have A.5′ to 3′ polymerase activity only B.both 5′ to 3′ polymerase activity and 3′ to 5′ exonuclease activity C.both 3′ to 5′ polymerase activity and 5′ to 3′ exonuclease activity D.both 3′ to 5′ polymerase activity and 5′ to 3′ polymerase activity

B.both 5′ to 3′ polymerase activity and 3′ to 5′ exonuclease activity

Telomerase is a ribonucleoprotein complex. The RNA component of the complex A. has reverse transcriptase activity B. provides structural support only C. forms a t-loop D. provides the template for telomere repeat synthesis

D. provides the template for telomere repeat synthesis

A type of mutation that results in multiple adjacent amino acid changes in a polypeptide is probably caused by the following type of mutation: A. frameshift B. transversion C. transition D. missense

A. frameshift

An induced mutation occurs A. as a result of natural processes in cells. B. as a result of interaction of DNA with an outside agent. C. spontaneously. D. as a result of DNA replication errors

B. as a result of interaction of DNA with an outside agent.

Translesion synthesis is mediated by A. error-prone DNA polymerases B. replicative DNA polymerases C. DNA glycosylase D. DNA photolyase E. RNA polymerases

A. error-prone DNA polymerases

In the mismatch repair pathway, DNA damage is recognized by A. RFC and PCNA B. exonuclease EXO1 C. MSH and MLH/PMS D. DNA polymerase E. Ku proteins

C. MSH and MLH/PMS

Repair of a DNA double-strand break by nonhomologous end-joining is initiated by A. the endonuclease Artemis. B. Ku70 and Ku80. C. DNA polymerase. D. DNA-dependent protein kinase catalytic subunit

B. Ku70 and Ku80.

One big (and real) difference between origins in eukaryotes and prokaryotes is: A. a prokaryotic closed circle of DNA usually only has one origin. B. eukaryotic DNA only has one origin C. origins are used for transcription in prokaryotes D. replication from a specific origin will occur many, many times before a cell divides in eukaryotes

A. a prokaryotic closed circle of DNA usually only has one origin.

The enzyme used in bacteria to directly fix thymine dimers A. Glycosylase B. Ku C. Photolyase D. Methyltransferase E. SPRTN Protease

C. Photolyase

Some mutations are very large and form abnormal chromosomes. An example of this is a mutation that results from a section of DNA being broken away from the chromosome and attaching to the end of a different chromosome. This is called a(n) A.deletion mutation B.duplication mutation C.inversion mutation D.translocation mutation E.abasic mutation

D.translocation mutation

In which level of gene expression control is chromosome position within the nucleus inside of chromosomal territories A.Level 1 B.Level 2 C.Level 3 D.Level 4

C.Level 3

A transversion mutation is one in which A. one pyrimidine base is replaced with another, or one purine base with another. B. one pyrimidine base is replaced with a purine base or vice versa. C. there is a C to T substitution. D. there is an A to G substitution

B. one pyrimidine base is replaced with a purine base or vice versa.

Which of the following is the appropriate direction for synthesis of DNA and RNA? A. 2’ to 5’ B. 3’ to 5’ C. 5’ to 2’ D. 5’ to 3’ E. 5’ to 4

D. 5’ to 3’

Bidirectional replication A. occurs only in prokayotes B. occurs only in eukaryotes C. occurs in both prokaryotes and eukaryotes D. only unidirection replication occurs in prokaryotes and eukaryotes!

C. occurs in both prokaryotes and eukaryotes

Which base deaminates to form uracil? A. adenosine B. cytosine C. thymine D. guanine

B. cytosine

Which of the following occupies the largest portion of the human genome? A. protein-coding sequences B. Introns C. Repeat sequences D. Gene regulatory sequences

C. Repeat sequences

Molecular Genetics Exam 2 Flashcards

(66 cards)