DNA Repair Mechanisms Quiz
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Questions and Answers

Enhancers can enhance any gene nearby by:

  • Methylating the DNA
  • Coding for regulators
  • Allowing maximum level of transcription (correct)
  • Blocking silencers

What is the role of silencers in gene regulation?

  • Activating transcription
  • Enhancing RNA processing
  • Promoting chromatin compaction
  • Blocking enhancers (correct)

Which process is inhibited by compact chromatin structure?

  • DNA repair
  • Gene translation
  • Transcription (correct)
  • Post-translational modifications

What is the function of RISC in gene regulation?

<p>Inducing gene silencing (D)</p> Signup and view all the answers

In bacterial gene regulation, most of the regulation occurs during:

<p>Transcription (C)</p> Signup and view all the answers

What is the main role of siRNA in gene regulation during a viral infection?

<p>Cleaving double-stranded RNA (A)</p> Signup and view all the answers

'Gene regulation in Bacteria' suggests that bacterial genes require:

<p>Continuous or regulated transcription (C)</p> Signup and view all the answers

Which type of mutation results in a stop codon?

<p>Nonsense mutation (C)</p> Signup and view all the answers

Which DNA repair mechanism involves genetic material swapping between homologous DNA molecules?

<p>Homologous recombination repair (B)</p> Signup and view all the answers

Which mutation causes a triplet code to code for the same amino acid as before?

<p>Silent mutation (D)</p> Signup and view all the answers

Which type of mutation replaces a pyrimidine with another pyrimidine or a purine with another purine?

<p>Transition mutation (C)</p> Signup and view all the answers

Which DNA repair mechanism occurs before replication of the DNA and repairs double-strand breaks?

<p>Nonhomologous end joining (B)</p> Signup and view all the answers

Which type of mutation results in a triplet code that codes for a different amino acid?

<p>Missense mutation (D)</p> Signup and view all the answers

Which type of mutation involves swapping a pyrimidine for a purine?

<p>Transversion mutation (D)</p> Signup and view all the answers

Which hypothesis states that mutations arise from adaptations to the environment?

<p>Lamarckism (B)</p> Signup and view all the answers

What type of control does a repressor protein exert on transcription?

<p>Negative control (C)</p> Signup and view all the answers

Which type of control initiates transcription through an activator protein?

<p>Positive control (C)</p> Signup and view all the answers

What is the role of chaperone proteins in the heat shock response?

<p>They inhibit sigma 32 at normal temperatures (A)</p> Signup and view all the answers

What is a riboswitch?

<p>A noncoding mRNA segment (D)</p> Signup and view all the answers

What happens to the usual sigma factor during the heat shock response?

<p>It is unstable at hot temperatures (B)</p> Signup and view all the answers

What is the role of the allosteric domain in activator proteins?

<p>It binds an allosteric compound (B)</p> Signup and view all the answers

What is an operon?

<p>A region of linked genes that are all under control of one promoter (B)</p> Signup and view all the answers

What is the role of the DNA binding domain in repressor proteins?

<p>It binds to regulatory DNA sequences (C)</p> Signup and view all the answers

Which of the following is a cause of spontaneous DNA mutations?

<p>Deamination of nucleotides (B)</p> Signup and view all the answers

What is the result of replication slippage during DNA replication?

<p>A daughter strand with less DNA (B)</p> Signup and view all the answers

What is a tautomeric shift in DNA?

<p>A spontaneous switch between different isomers of purines and pyrimidines (B)</p> Signup and view all the answers

What is the result of depurination in DNA?

<p>A nucleotide loses a purine (C)</p> Signup and view all the answers

Which of the following is an example of an induced DNA mutation?

<p>Base analogs (B)</p> Signup and view all the answers

What is the effect of deaminating agents on DNA?

<p>They remove amino groups from nucleotides (C)</p> Signup and view all the answers

What is the effect of alkylating agents on DNA?

<p>They add bulky carbon chains to bases (A)</p> Signup and view all the answers

Which of the following is a common cause of induced DNA mutations?

<p>UV radiation (C)</p> Signup and view all the answers

What is the role of the Lac operon?

<p>To encode for the enzyme that degrades lactose into glucose and galactose (C)</p> Signup and view all the answers

What happens when glucose is present in high levels?

<p>The Lac operon turns off (B)</p> Signup and view all the answers

What is the role of the CRP-cAMP complex?

<p>It binds to the lac promoter and turns on the Lac operon (C)</p> Signup and view all the answers

What is the function of the LacI protein?

<p>It turns off the Lac operon (D)</p> Signup and view all the answers

What is the effect of allo-lactose on the Lac operon?

<p>It turns on the Lac operon (A)</p> Signup and view all the answers

What genes are included in the Lac operon?

<p>lacZ, lacY, and lacA (B)</p> Signup and view all the answers

What happens in the absence of the CRP-cAMP complex?

<p>Transcription of lacZYA is very low (B)</p> Signup and view all the answers

What is the effect of a mutant promoter sequence (P-) on the Lac operon?

<p>It decreases transcription (C)</p> Signup and view all the answers

Flashcards

Spontaneous Mutations

Naturally occurring changes during DNA replication.

Replication Slippage

Template strand forms loops during DNA replication, leading to missed DNA segments.

Tautomeric Shifts

Spontaneous switching between purine and pyrimidine isomers, leading to non-complementary base pairing.

Depurination

Random loss of a purine base from DNA.

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Deamination

Random loss of an amino group from a base, causing a change in the base.

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Induced Mutations

Mutations caused by external factors like chemicals, radiation, or transposable elements.

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Base Analogs

Chemicals that replace purines or pyrimidines in DNA.

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Deaminating Agents

Chemicals that remove amino groups from DNA bases.

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Alkylating Agents

Chemicals that add bulky carbon chains to DNA bases.

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Trans-acting Elements

Coding regions of DNA that code for regulators.

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Enhancers

DNA sequences that allow full transcription of genes.

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Silencers

DNA sequences that block enhancers, restricting gene expression.

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RNA Interference

Process of regulating gene expression by using RNA.

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siRNA

Double-stranded RNA that is produced during viral infection.

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microRNA

Non-coding RNA that inhibits gene expression.

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RISC

RNA-induced silencing complex, involved in RNA interference.

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RITS

RNA-induced transcriptional silencing complex, involved in RNA interference.

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Gene Regulation in Bacteria

Regulation of gene expression in bacteria that mainly occurs during transcription.

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Promoter and Operator

DNA sequences involved in regulating gene expression in bacteria.

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Lac Operon

A group of genes in bacteria that encode enzymes for lactose metabolism.

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β-galactosidase

An enzyme encoded by the Lac operon that breaks down lactose.

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cAMP

A molecule that accumulates when glucose is absent, activating the Lac operon.

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CRP

A protein that binds cAMP and helps activate the Lac operon.

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LacI

A protein that represses the Lac operon in the absence of lactose.

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DNA Repair

The process of repairing damaged DNA.

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Homologous Recombination Repair

A DNA repair mechanism where genetic material is swapped between homologous chromosomes.

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Nonhomologous End Joining

A DNA repair mechanism that joins broken ends of DNA without using a template.

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Random Mutation Hypothesis

Mutations arise randomly, not in response to environmental needs.

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Adaptation Hypothesis

Mutations arise due to adaptation to the environment.

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Missense Mutation

A mutation that changes a base, resulting in a different amino acid.

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Nonsense Mutation

A mutation that changes a base, resulting in a stop codon.

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Silent Mutation

A mutation that changes a base, but results in the same amino acid.

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Transition Mutation

A mutation where a pyrimidine is replaced by another pyrimidine or a purine by another purine.

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Transversion Mutation

A mutation where a pyrimidine is replaced by a purine or vice versa.

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Negative Control

Regulation of gene expression where a repressor protein inhibits transcription.

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Positive Control

Regulation of gene expression where an activator protein initiates transcription.

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Heat Shock Response

A cellular response to high temperatures that activates expression of stress-related genes.

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Riboswitches

Noncoding RNA sequences that directly bind a metabolite and control downstream gene expression.

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Study Notes

Types of Mutations

  • Spontaneous mutations occur naturally during DNA replication
  • Replication slippage: template strand forms loops, leading to missed DNA segments and resulting in diseases like Fragile-X syndrome and Huntington's disease
  • Tautomeric shifts: spontaneous switches between purine and pyrimidine isomers, causing non-complementary base pairing
  • Depurination: random loss of purine, filled with adenine by DNA polymerase
  • Deamination: random loss of amino group, resulting in base changes (e.g., cytosine to uracil)

Induced Mutations

  • Occur due to chemical mutagens, radiation, or transposable DNA elements
  • Base analogs: replace purines or pyrimidines, increase tautomeric shifts and UV radiation sensitivity
  • Deaminating agents: remove amino groups
  • Alkylating agents: add bulky carbon chains to bases
  • Trans-acting elements: coding regions of DNA that code for regulators
  • Enhancers: allow for maximum transcription level, can enhance any nearby gene
  • Silencers: block enhancers, restricting enhancement to target genes

RNA Interference

  • RNA-induced gene silencing: regulates translation
  • siRNA: forms during viral infection, produces double-stranded RNA, cleaved by dicer
  • microRNA: non-coding RNA, inhibits gene expression
  • RISC: RNA-induced silencing complex
  • RITS: RNA-induced transcriptional silencing complex

Gene Regulation in Bacteria

  • Most regulation occurs during transcription
  • Two types of transcriptional regulation: promoter and operator
  • Lac operon: encodes for β-galactosidase, degrades lactose into glucose and galactose
  • Lac operon is usually off, but turns on in the presence of lactose and absence of glucose
  • Glucose inhibits production of adenylate cyclase, which produces cAMP
  • cAMP binds to CRP, and the complex binds to the lac promoter, turning on the lac operon
  • Lac operon is repressed by lacI, and induced by allo-lactose

DNA Repair

  • Two types: homologous recombination repair and nonhomologous end joining
  • Homologous recombination: genetic material swapped between homologous DNA molecules
  • Nonhomologous end joining: occurs in G1, repairs double-strand breaks

Mutation Hypotheses

  • Luria and Delbrück proved the random mutation hypothesis
  • Adaptation hypothesis: mutations arise from adaptations to the environment
  • Random mutation hypothesis: mutations occur randomly and not in response to the environment

Types of Mutations

  • Missense: changes a base, resulting in a different amino acid
  • Nonsense: changes a base, resulting in a stop codon
  • Silent: changes a base, resulting in the same amino acid
  • Transition: a pyrimidine replaces another pyrimidine or a purine replaces another purine
  • Transversion: a pyrimidine is swapped for a purine

Gene Regulation

  • Negative control: repressor protein binds to DNA, inhibiting transcription
  • Positive control: activator protein binds to DNA, initiating transcription
  • Heat shock response: abnormally hot temperatures activate expression of heat stress genes
  • Riboswitches: noncoding mRNA segments that control downstream gene expression by binding a metabolite

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Genetics Exam 3

Description

Test your knowledge on the DNA repair mechanisms including homologous recombination and nonhomologous end joining. Learn about the process of genetic material swap and repair of double strand breaks in different organisms.

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