أسئلة المحاضرة التاسعة جينتكس (قبل التعديل)
60 Questions
0 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to Lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What does a permanent change of the base sequence of nucleotides refer to?

  • Chromosomal crossover
  • DNA replication
  • Gene mutation (correct)
  • Transcription process

Which of the following best describes the function of DNA repair mechanisms?

  • To facilitate gene expression
  • To replicate DNA
  • To fix mutations in the DNA sequence (correct)
  • To remove non-coding regions

Which process is NOT involved in DNA repair?

  • RNA splicing (correct)
  • Base excision repair
  • Nucleotide excision repair
  • Mismatch repair

Which statement is true regarding mutations?

<p>Mutations might lead to beneficial traits. (A)</p> Signup and view all the answers

What is NOT a common cause of mutations?

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

What occurs as a result of breaking a phosphate diester bond in the DNA backbone?

<p>The DNA strand is fragmented. (C)</p> Signup and view all the answers

What is a consequence of altered or deleted bases in a DNA sequence?

<p>The protein's amino acid sequence may remain unchanged. (D)</p> Signup and view all the answers

Which term describes a mutation that results in changing one codon to another but codes for the same amino acid?

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

Which of the following statements is false regarding altered bases in DNA?

<p>They always result in a significant change in protein function. (C)</p> Signup and view all the answers

What best describes the role of phosphate diester bonds in DNA?

<p>They connect the sugar molecules of adjacent nucleotides. (D)</p> Signup and view all the answers

What is the primary role of DNA repair mechanisms?

<p>To correct damage that occurs to the DNA structure. (C)</p> Signup and view all the answers

Which of the following statements about DNA repair is false?

<p>Only specific types of cells possess the ability to repair DNA. (D)</p> Signup and view all the answers

Which mechanism is commonly involved in the DNA repair process?

<p>Nucleotide excision repair (C)</p> Signup and view all the answers

What consequence can result from inefficient DNA repair processes?

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

Which of the following is NOT a major type of DNA damage that repair mechanisms address?

<p>Methylation of histones (B)</p> Signup and view all the answers

What is the primary function of DNA polymerase beta in DNA repair?

<p>To fill gaps with correct nucleotides (B)</p> Signup and view all the answers

Which enzyme is responsible for the ligation process in DNA repair?

<p>DNA ligase (D)</p> Signup and view all the answers

What is the order of operations when repairing damaged DNA?

<p>Nucleotide filling followed by ligation (D)</p> Signup and view all the answers

What role does DNA ligase play in the context of DNA repair?

<p>It seals nicks in the DNA backbone (B)</p> Signup and view all the answers

Which statement about damaged DNA repair is incorrect?

<p>Ligase removes damaged nucleotides. (C)</p> Signup and view all the answers

What is the primary role of mismatch repair mechanisms?

<p>To correct errors made during DNA replication (B)</p> Signup and view all the answers

What type of repair is base excision repair (BER) specifically responsible for?

<p>Targeting individual damaged nucleotides for removal and replacement (D)</p> Signup and view all the answers

Which of the following accurately describes nucleotide excision repair (NER)?

<p>It removes short oligonucleotides containing damage (D)</p> Signup and view all the answers

Which statement is true regarding the types of DNA repair mechanisms?

<p>Nucleotide excision repair can handle a broader range of lesions than base excision repair (D)</p> Signup and view all the answers

What distinguishes excision repair from mismatch repair mechanisms?

<p>Excision repair repairs damage caused by external factors, while mismatch repair corrects replication errors (A)</p> Signup and view all the answers

What is the primary role of DNA ligase in DNA replication?

<p>To seal breaks left by DNA polymerase (C)</p> Signup and view all the answers

Which disease is associated with defects in DNA mismatch repair?

<p>Hereditary Non-Polyposis Colon Cancer (HNPCC) (C)</p> Signup and view all the answers

What can be concluded about the role of DNA mismatch repair mechanisms?

<p>They help correct errors during DNA replication (C)</p> Signup and view all the answers

What is a key consequence of malfunctioning DNA mismatch repair systems?

<p>Accumulation of mutations leading to cancer (B)</p> Signup and view all the answers

Which statement accurately describes DNA ligase's function in the DNA replication process?

<p>It seals nicks to create a continuous DNA strand (D)</p> Signup and view all the answers

Which type of agent is primarily responsible for causing mutations?

<p>All of the above (D)</p> Signup and view all the answers

Which category does NOT typically include environmental factors known to induce mutations?

<p>Genetic agents (D)</p> Signup and view all the answers

In the context of mutation types, what is the main distinction between physical, chemical, and biological agents?

<p>Their mechanism of action (C)</p> Signup and view all the answers

Which statement best describes the relationship between chemical agents and mutations?

<p>Chemical agents can interact with DNA and alter its structure (B)</p> Signup and view all the answers

Which of the following is considered a biological agent that can cause mutations?

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

What is the primary effect of UV exposure on adjacent pyrimidines in DNA?

<p>Covalent joining of adjacent pyrimidines (C)</p> Signup and view all the answers

What structural change in DNA is caused by the formation of thymine dimers?

<p>Kink or distortion in the DNA helix (B)</p> Signup and view all the answers

What can occur if thymine dimers in DNA are not repaired?

<p>Permanent mutation leading to hereditary disorders (A)</p> Signup and view all the answers

Which of the following best describes a thymine dimer's role in DNA damage?

<p>Formation of covalent bonds causing structural distortion (A)</p> Signup and view all the answers

What is a potential long-term consequence of repeated exposure to UV light on DNA?

<p>Increased likelihood of cancer due to hereditary disorders (C)</p> Signup and view all the answers

What is the primary function of excision repair mechanisms in DNA?

<p>To remove and replace nucleotides damaged by exogenous agents (B)</p> Signup and view all the answers

Which type of repair specifically deals with single base lesions in DNA?

<p>Base excision repair (BER) (B)</p> Signup and view all the answers

Which of the following statements best describes nucleotide excision repair (NER)?

<p>NER removes bulky DNA adducts and helix-distorting lesions. (C)</p> Signup and view all the answers

What distinguishes base excision repair (BER) from mismatch repair (MMR)?

<p>BER repairs single nucleotide changes, while MMR corrects mismatched base pairs. (D)</p> Signup and view all the answers

Which best describes the mechanism by which mismatch repair systems function?

<p>They identify and excise incorrectly paired bases after DNA synthesis. (C)</p> Signup and view all the answers

What consequence is primarily associated with marked sensitivity to ultraviolet light?

<p>High susceptibility to skin damage (C)</p> Signup and view all the answers

Which of the following is NOT a potential outcome of ultraviolet light exposure?

<p>Improvement in skin elasticity (B)</p> Signup and view all the answers

What are the long-term risks associated with continuous exposure to ultraviolet rays?

<p>Potential for multiple skin cancers (D)</p> Signup and view all the answers

Which statement accurately reflects the consequences of ultraviolet light sensitivity?

<p>It can lead to dire health issues such as skin cancers and premature death. (D)</p> Signup and view all the answers

Which of the following is a characteristic of sensitivity to ultraviolet sunlight?

<p>Increased development of skin diseases (C)</p> Signup and view all the answers

What is a potential consequence of ineffective DNA repair mechanisms on cellular function?

<p>Increased risk of uncontrolled cell division (C)</p> Signup and view all the answers

Which of the following statements about nucleotide excision repair (NER) is accurate?

<p>NER removes a short single-strand segment of DNA containing damage (A)</p> Signup and view all the answers

What is the first step carried out by the DNA mismatch repair nuclease complex when it encounters damaged bases?

<p>Recognizing and binding to the damaged base (D)</p> Signup and view all the answers

In the context of base excision repair (BER), what is the primary function of DNA glycosylases?

<p>To remove damaged bases from the DNA strand (A)</p> Signup and view all the answers

In the context of DNA mismatch repair, which process occurs after the binding of the nuclease complex?

<p>Excision of the damaged base or bases (D)</p> Signup and view all the answers

Which specific activity does the endo then exo nuclease refer to in DNA mismatch repair?

<p>Initial incision followed by a further excision (C)</p> Signup and view all the answers

What distinguishes mismatch repair (MMR) from other DNA repair mechanisms?

<p>MMR identifies and corrects improperly paired nucleotides after replication (D)</p> Signup and view all the answers

Which of these processes is least likely involved in the repair of DNA double-strand breaks?

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

What is the role of the DNA mismatch repair nuclease in maintaining genetic integrity?

<p>It prevents the replication of damaged DNA (B)</p> Signup and view all the answers

Which of the following scenarios accurately describes a consequence of improper functioning of the DNA mismatch repair nuclease complex?

<p>Increased mutation rates due to unresolved errors (D)</p> Signup and view all the answers

Flashcards

DNA Repair

The process of fixing changes in the DNA sequence.

Base Sequence Change

A permanent alteration of the order of nucleotides in DNA.

Nucleotides

The building blocks of DNA.

Genetic Change

A mutation occurring due to alterations in nucleotide order.

Signup and view all the flashcards

Mutation

A permanent change in the DNA sequence.

Signup and view all the flashcards

DNA backbone break

A break in the chemical bonds holding together the DNA structure.

Signup and view all the flashcards

Altered bases

Changes in the chemical building blocks of DNA.

Signup and view all the flashcards

Deleted bases

Missing chemical building blocks in the DNA.

Signup and view all the flashcards

Silent mutation

A change in DNA that doesn't affect the resulting protein.

Signup and view all the flashcards

Changing one codon

A change in a set of three letters (codon) coding for an amino acid.

Signup and view all the flashcards

DNA damage

A change or break in the structure of DNA, affecting the sequence of nucleotides.

Signup and view all the flashcards

DNA polymerase beta

An enzyme that fills in missing nucleotides during DNA repair.

Signup and view all the flashcards

DNA ligase

An enzyme that joins DNA fragments together during repair.

Signup and view all the flashcards

Gap Filling

The process of adding missing nucleotides to a damaged DNA strand.

Signup and view all the flashcards

Why is DNA Repair Important?

DNA repair is essential for maintaining the integrity of genetic information. It protects against mutations that can lead to diseases like cancer or developmental problems.

Signup and view all the flashcards

What are the Different Types of DNA Repair?

Various mechanisms exist to fix different types of DNA damage. Some examples include base excision repair, nucleotide excision repair, and mismatch repair.

Signup and view all the flashcards

What Happens When DNA Repair Fails?

If DNA repair mechanisms malfunction, errors accumulate in the DNA sequence. This can lead to mutations, which might cause various diseases.

Signup and view all the flashcards

How do Cells Know When to Repair DNA?

Cells have specialized enzymes that detect damaged DNA and initiate repair processes. These enzymes recognize specific types of damage and activate the appropriate repair pathway.

Signup and view all the flashcards

Mismatch Repair

Fixes errors that occur during DNA replication, like when the wrong nucleotide is accidentally added.

Signup and view all the flashcards

Excision Repair

Removes damaged DNA segments caused by external factors like UV light or chemicals.

Signup and view all the flashcards

Nucleotide Excision Repair (NER)

Removes a larger segment of DNA, including the damaged bases and surrounding nucleotides, then replaces it with the correct sequence.

Signup and view all the flashcards

What are the two main categories of DNA repair processes?

DNA repair processes are broadly categorized into mismatch repair and excision repair.

Signup and view all the flashcards

DNA mismatch repair

A crucial process that corrects errors made during DNA replication, ensuring the genetic code is accurate.

Signup and view all the flashcards

Hereditary Non-Polyposis Colon Cancer (HNPCC)

An inherited condition caused by defects in DNA mismatch repair, increasing the risk of developing colon cancer.

Signup and view all the flashcards

What happens if DNA mismatch repair is defective?

Mutations can accumulate unchecked, leading to increased risk of cancer and other genetic diseases.

Signup and view all the flashcards

How does DNA ligase contribute to DNA replication?

It joins the newly synthesized DNA fragments together, creating a continuous DNA strand.

Signup and view all the flashcards

Mutation Cause

A physical, chemical, or biological agent that can alter the DNA sequence, leading to mutations.

Signup and view all the flashcards

Types of Mutagens

Agents that cause mutations can be classified into three categories: physical, chemical, and biological.

Signup and view all the flashcards

Physical Mutagens

Physical agents that cause mutations include ionizing radiation (like X-rays) and UV light.

Signup and view all the flashcards

Chemical Mutagens

Chemical substances that can alter DNA structure and lead to mutations.

Signup and view all the flashcards

Biological Mutagens

Biological agents like viruses and bacteria can cause mutations by inserting their genetic material into the host's DNA.

Signup and view all the flashcards

Base Excision Repair (BER)

Fixes damaged or altered bases in DNA, mainly those caused by oxidation or alkylation.

Signup and view all the flashcards

What are the two main types of DNA repair?

DNA repair can broadly be categorized into mismatch repair and excision repair.

Signup and view all the flashcards

UV Damage to DNA

Ultraviolet (UV) radiation can cause covalent bonds to form between adjacent pyrimidines in DNA, creating thymine dimers. These dimers distort the DNA helix, potentially leading to mutations.

Signup and view all the flashcards

Thymine Dimers

Thymine dimers are covalent bonds formed between adjacent thymine bases in DNA, resulting from UV radiation damage. These dimers cause a kink or distortion in the DNA helix.

Signup and view all the flashcards

Mutations from UV Damage

If DNA damage caused by UV radiation, like thymine dimers, is not repaired, it can lead to permanent changes in the DNA sequence called mutations.

Signup and view all the flashcards

Hereditary Disorders

Unrepaired mutations in DNA can be inherited, meaning they can be passed down to offspring. These mutations can lead to hereditary disorders.

Signup and view all the flashcards

DNA Repair Importance

Repairing UV-induced DNA damage, like thymine dimers, is crucial to prevent mutations and potential hereditary disorders. This process maintains the integrity of the genetic code.

Signup and view all the flashcards

DNA Mismatch Repair Nuclease

A complex of enzymes that recognizes, binds, and removes damaged DNA bases during mismatch repair.

Signup and view all the flashcards

Endo then Exo

The method used by DNA mismatch repair nucleases to excise damaged bases: they first cut the DNA backbone on either side of the damage (endo), then remove the damaged DNA segment (exo).

Signup and view all the flashcards

What causes DNA damage?

DNA damage can occur due to various factors, including radiation, chemicals, and even naturally occurring errors during DNA replication.

Signup and view all the flashcards

Sun Sensitivity

A heightened susceptibility to the harmful effects of sunlight, particularly ultraviolet radiation.

Signup and view all the flashcards

Skin Damage

Injury to the skin caused by excessive exposure to sunlight, leading to sunburn, premature aging, and potentially skin cancer.

Signup and view all the flashcards

Multiple Skin Cancers

The development of several different types of skin cancer due to prolonged and excessive sun exposure.

Signup and view all the flashcards

Premature Death

Death occurring earlier than expected due to health problems caused by excessive sun exposure, such as skin cancers and other related diseases.

Signup and view all the flashcards

DR

An abbreviation often used in medical contexts to denote "Doctor".

Signup and view all the flashcards

Study Notes

DNA Mutation

  • DNA mutation is a permanent change in the base sequence of nucleotides.
  • Mutations can be categorized by size:
    • Gross mutations occur at the chromosome level.
    • Small mutations occur at the DNA level.
  • Spontaneous mutations arise from uncorrected replication errors.
  • Induced mutations are caused by external mutagens:
    • Physical mutagens (e.g., ionizing radiation like gamma and X-rays, non-ionizing radiation like UV radiation, electromagnetic radiation from mobile phones, satellites and computers).
    • Chemical mutagens (e.g., carcinogens like cigarette smoke).
    • Biological mutagens (e.g., viruses like Hepatitis C Virus (HCV) leading to Hepatocellular carcinoma (HCC), Human papilloma virus (HPV) linked to cervical cancer, bacteria like H. pylori causing gastric cancer).

Types of DNA Damage

  • DNA damage can lead to breaks in the phosphate diester bonds of the DNA backbone.
  • Base changes or deletions can also occur.
  • Point mutations involve changes in a single codon:
    • Silent mutations do not affect protein production as the amino acid remains the same.
    • Missense mutations lead to a change in one amino acid.
    • Nonsense mutations change a normal codon to a stop codon.
    • Sense mutations change a termination codon to one that codes for an amino acid.
  • UV radiation can cause adjacent pyrimidines to form thymine dimers, distorting the DNA helix.
  • If damage is not repaired, permanent mutations can lead to hereditary disorders.

DNA Repair

  • DNA repair involves enzymes that scan for damage, recognize it, remove it, and resynthesize the DNA.
  • Enzymes such as endonucleases, exonucleases, DNA polymerase, and ligase are crucial for this process.
    • Endonucleases recognize and cut the damaged strand.
    • Exonucleases remove the damaged section.
    • DNA polymerase fills in the gap.
    • Ligase seals the gap.
  • Mismatch repair corrects errors during replication.
  • Excision repair corrects damage from exogenous agents (e.g., chemical or physical):
    • Base excision repair (BER) corrects base errors (e.g., X-ray errors).
    • Nucleotide excision repair (NER) corrects larger defects like thymine dimers caused by UV radiation or chemical mutagens.
  • Xeroderma pigmentosum (XP) is an autosomal recessive condition caused by the deficiency of a UV-specific endonuclease.
  • XP leads to high sensitivity to sunlight, skin damage, multiple skin cancers, and premature death.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Quiz Team

Related Documents

Genetics Lecture (9) PDF

More Like This

DNA Damage and Mutation Types Quiz
13 questions

DNA Damage and Mutation Types Quiz

ExaltingVictory avatar
ExaltingVictory
Lecture 3: DNA Damage and Repair
18 questions

Lecture 3: DNA Damage and Repair

SpontaneousBaltimore avatar
SpontaneousBaltimore
Lecture 9
74 questions

Lecture 9

ClaraJeniffer1 avatar
ClaraJeniffer1
Use Quizgecko on...
Browser
Open
Browser
Browser