Questions and Answers
Define mutation and mutagen.
Mutation - A change in a gene or chromosome; Mutagen - A chemical or physical agent that interacts with DNA and causes a mutation.
List three examples of mutagens.
UV radiation, X-rays, cigarette smoke.
Identify three types of chromosomal alterations.
Duplication, inversion, insertion.
Distinguish among silent, missense, and nonsense point mutations.
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What is a frameshift mutation? What causes this type of mutation?
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Assume that a point mutation changes the codon AUU to AUC. Why is this a neutral mutation?
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Describe how the insertion of A after the start codon AUG affects the encoded amino acid sequence: AUG-GUC-CCU-AAA !AUG-AGU-CCC-UAA-A.
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Compare and contrast germline mutations and somatic mutations.
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Study Notes
Mutations and Mutagens
- Mutation: A change in a gene or chromosome that can affect an organism's traits.
- Mutagen: A chemical or physical agent that interacts with DNA, leading to mutations.
Examples of Mutagens
- UV Radiation: High-energy light that can cause DNA damage.
- X-rays: A form of radiation that can lead to genetic alterations.
- Cigarette Smoke: Contains harmful chemicals that can cause mutations.
Chromosomal Alterations
- Duplication: A segment of the chromosome is repeated, leading to extra genetic material.
- Inversion: A segment of the chromosome breaks off, flips around, and reattaches, altering gene order.
- Insertion: Extra DNA is added into a gene sequence, which can disrupt normal function.
Point Mutations
- Silent Mutation: A change in the nucleotide that does not alter the amino acid sequence due to redundancy in genetic code.
- Missense Mutation: A change that results in the substitution of one amino acid for another, potentially impacting protein function.
- Nonsense Mutation: A change that introduces a premature stop codon, leading to truncated proteins.
Frameshift Mutation
- Definition: A genetic mutation resulting from insertions or deletions (indels) of nucleotides, which alters the reading frame of the gene.
- Causes: Indels that shift the normal grouping of codons.
Neutral Mutation
- Changing the codon from AUU to AUC may result in a silent mutation, which does not affect the protein's function since both codons code for the same amino acid (Isoleucine).
Effects of Insertion Mutation
- Insertion after the start codon (AUG) can lead to a missense mutation, altering the encoded amino acid sequence from AUG-GUC-CCU-AAA to AUG-AGU-CCC-UAA.
Germline vs. Somatic Mutations
- Germline Mutations: Occur in germ cells (sperm and egg), can be passed to offspring, leading to hereditary conditions.
- Somatic Mutations: Occur in body cells and are not inherited, affecting only the individual organism.
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Test your knowledge on mutations and mutagens with these flashcards. Explore definitions, examples of mutagens, and types of chromosomal alterations. Perfect for reviewing key concepts in biology chapter 7.3.