Chp. 13 - Exam 3 Bio 190
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Questions and Answers

What did the Lederbergs' experiment demonstrate about mutations?

  • Mutations are induced by external factors.
  • Mutations only occur in E. coli.
  • Mutations occur exclusively in response to viral infections.
  • Mutations are random events. (correct)

Spontaneous mutations are caused solely by external agents.

False (B)

What are the two main types of mutations discussed?

Spontaneous and induced mutations.

The process used by the Lederbergs to show that mutations are random events is called ______.

<p>replica plating</p> Signup and view all the answers

What role do Mismatch Repair proteins play in DNA mutation?

<p>They reverse direct nucleotide insertion errors. (B)</p> Signup and view all the answers

Which type of mutation involves a change where one base is replaced by another?

<p>Base substitution (A)</p> Signup and view all the answers

Mutations can be locked into the genome if DNA replication continues without repair.

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

Mutations in somatic cells can be transmitted to offspring.

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

What is one example of an induced mutation?

<p>A mutation caused by exposure to radiation.</p> Signup and view all the answers

What is the most common DNA repair system found in all living organisms?

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

Match the type of mutation to its description:

<p>Spontaneous Mutations = Occur naturally without external influence Induced Mutations = Result from external agents such as chemicals or radiation</p> Signup and view all the answers

A mutation that does not affect the amino acid sequence of a protein is known as a _____ mutation.

<p>silent</p> Signup and view all the answers

Match the type of mutation with its description:

<p>Silent mutation = No change to amino acid sequence Missense mutation = Changes one amino acid in the polypeptide Nonsense mutation = Introduces a premature stop codon Frameshift mutation = Alters reading frame due to base addition or deletion</p> Signup and view all the answers

What condition is required for mutations to become permanent in the genome?

<p>DNA damage is not repaired before replication continues. (D)</p> Signup and view all the answers

The virus that infects bacteria and was used in the Lederbergs' experiment is called ______.

<p>T1 bacteriophage</p> Signup and view all the answers

What is one effect of mutations in noncoding sequences?

<p>They may affect gene expression. (C)</p> Signup and view all the answers

Point mutations can only involve the addition or deletion of base pairs.

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

At what stage do mutations occur that can be transmitted to offspring?

<p>During meiosis</p> Signup and view all the answers

Nucleotide excision repair (NER) involves the removal of a damaged ______ before resynthesis.

<p>strand</p> Signup and view all the answers

What happens to the intact strand during nucleotide excision repair?

<p>It serves as a template for resynthesis. (C)</p> Signup and view all the answers

What is the original error rate of DNA polymerase before proofreading?

<p>1 error/100,000 basepairs (A)</p> Signup and view all the answers

Proofreading by DNA polymerase reduces the error rate to 1 error per billion basepairs.

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

What are transposons commonly referred to as?

<p>jumping genes</p> Signup and view all the answers

The repair DNA polymerase can insert wrong __________.

<p>nucleotide(s)</p> Signup and view all the answers

Which of the following statements is true regarding mutations?

<p>Mutations can occur outside the coding sequence. (B)</p> Signup and view all the answers

Mutations always create a new protein with a different function.

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

How many ways does Section 13.1 outline how mutations can affect the sequence of a gene?

<p>four</p> Signup and view all the answers

A __________ can occur when a chromosome is broken.

<p>mutation</p> Signup and view all the answers

What is one potential consequence of mutations on proteins?

<p>They can cause changes in the amino acid sequence. (D)</p> Signup and view all the answers

Flashcards

Mutations

Changes in the DNA sequence.

Spontaneous Mutations

Mutations that occur naturally without any outside influence.

Induced Mutations

Mutations caused by external factors like chemicals or radiation.

Lederbergs’ experiment

An experiment showing mutations are random events.

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Replica plating

A technique to identify bacterial colonies with specific traits.

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Random theory of mutation

The idea that mutations happen randomly.

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DNA damage

Physical or chemical changes to the DNA molecule.

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Mismatch Repair

A system to correct errors during DNA replication.

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DNA polymerases

Enzymes that build DNA.

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T1 bacteriophage

Virus that infects bacteria.

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DNA polymerase error rate

The frequency at which DNA polymerase inserts the wrong nucleotide during replication.

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Proofreading by DNA polymerase

The ability of DNA polymerase to detect and correct errors during DNA replication.

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Transposons

Segments of DNA that can move around within the genome, often disrupting gene function.

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Chromosome break

A break in the DNA molecule that can lead to mutations if it's not repaired correctly.

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Consequences of mutations

The ways in which mutations can affect gene function and the organism's traits.

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Mutation affecting gene sequence

A mutation that changes the order of nucleotides in a gene.

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Mutation affecting amino acid sequence

A mutation that changes the amino acid sequence of a protein.

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Mutation affecting gene expression

A mutation that affects how much or when a gene is expressed.

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Mutations outside the coding sequence

Mutations that occur in regions of DNA that don't directly code for proteins.

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Somatic Mutations

Mutations that occur in body cells (not sperm or egg cells). These mutations can affect the individual but are not passed on to offspring.

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Germ-line Mutations

Mutations that occur in sperm or egg cells. These mutations are passed down to offspring and affect every cell in the individual.

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Point Mutation

A change in a single base pair within the DNA sequence.

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Base Substitution

A type of point mutation where one base is replaced by another.

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Frameshift Mutation

A mutation that shifts the reading frame of a gene, altering the amino acid sequence and potentially creating a non-functional protein.

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Silent Mutation

A point mutation that doesn't change the amino acid sequence of a protein.

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Missense Mutation

A point mutation that changes the amino acid sequence of a protein, possibly altering its function.

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Nonsense Mutation

A point mutation that introduces a premature stop codon, resulting in a shortened and likely non-functional protein.

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Nucleotide Excision Repair (NER)

A DNA repair system that removes damaged DNA segments and replaces them with correct sequences using the undamaged strand as a template.

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Why is DNA Repair Important?

DNA repair systems are crucial for maintaining the integrity of genetic information and preventing harmful mutations. They help protect cells from damage and ensure proper gene expression.

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Study Notes

Chapter 13: Altering the Genetic Material: Mutation and DNA Repair

  • This chapter covers mutations and DNA repair mechanisms.
  • The Lederbergs' experiments demonstrated that mutations are random events.

13.2 Causes of Mutations: The Lederbergs Showed That Mutations Are Random Events

  • Joshua and Esther Lederberg's experiments investigated the cause of mutations in E. coli cells resistant to T1 bacteriophage.
  • Their experiments supported the random theory of mutation.
  • The studies involved replica plating, which showed that mutations occurred before exposure to the virus.

13.2 Causes of Mutations: The Lederbergs Used Replica Plating to Show That Mutations Are Random Events

  • Replica plating was a technique used by Lederbergs.
  • In replica plating, a velvet cloth was used to create a replica of bacterial colonies on a master plate.
  • The replicas were then placed onto secondary plates with T1 bacteriophage to identify resistant colonies.
  • The results showed that resistant colonies were already present on the master plate before contact with the bacteriophage. This confirmed mutations occurred randomly.

How do mutations occur?

  • Usually, DNA damage precedes mutations.
  • DNA damage can be repaired through various repair mechanisms.
  • Mutations can be fixed or become permanent.
  • Spontaneous mutations include errors during DNA replication, toxic metabolic products, and changes in nucleotide structure.
  • Induced mutations come from chemical agents (e.g., benzo(a)pyrene) and physical agents (e.g., UV light, X-rays).

13.3 DNA Repair

  • All living organisms have DNA repair mechanisms.
  • Cells contain various systems to detect and repair DNA damage.
  • Common types of DNA repair include direct repair, base excision repair, nucleotide excision repair, and mismatch repair. Examples of DNA repair pathways are nucleotide excision repair (NER).

13.1 Consequences of Mutations: Gene Mutations Alter the DNA Sequence of a Gene

  • Point mutations affect a single base pair.
  • Base substitutions replace one base with another.
  • Single-base insertions or deletions cause frameshift mutations.

13.1 Consequences of Mutations: Gene Mutations May Affect the Amino Acid Sequence of a Polypeptide

  • Silent mutations do not change the amino acid sequence.
  • Missense mutations change one amino acid.
  • Nonsense mutations introduce a premature stop codon.
  • Frameshift mutations alter the reading frame, causing significant changes in the amino acid sequence.

13.1 Consequences of Mutations: Gene Mutations That Occur Outside of Coding Sequences Can Influence Gene Expression

  • Mutations in non-coding regions can affect gene expression.
  • Promoter, transcriptional regulatory elements, splice sites, and translational regulatory elements are examples of non-coding DNA sequences that can be affected by mutations.
  • Changes in these regions can alter transcription, mRNA splicing, translation, or other aspects of gene expression.

13.1 When do mutations occur?

  • Mutations during meiosis (gamete formation) affect offspring but not the individual.
  • Mutations in somatic cells during mitosis affect the individual but not their offspring.

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Related Documents

Chapter 13 Notes - Exam 3 PDF

Description

Explore the intricate processes of mutations and DNA repair in this detailed quiz based on Chapter 13. Learn about the groundbreaking experiments by Lederberg that unveiled the randomness of mutations in E. coli cells. Test your knowledge on techniques such as replica plating and their implications in genetics.

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