Types of Small Mutations in a Single Gene
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Questions and Answers

What is the effect of a point mutation in the non-coding region of a gene?

  • It has no effect on the gene's function.
  • It always results in a silent mutation.
  • It can change protein binding sites, promoter sequences, or splice sites. (correct)
  • It always results in a change in the amino acid sequence.

    • What is an example of a missense mutation?

  • CGA (Arg) >>> UGA (Stop)
  • CGA (Arg) >>> CCA (Pro) (correct)
  • CGA (Arg) >>> CGG (Arg)
  • CGA (Arg) >>> CGA (Arg)

    • What is the effect of a frameshift mutation?

  • It changes the amino acid sequence.
  • It has no effect on the gene's function.
  • It always results in a silent mutation.
  • It shifts the reading frame. (correct)

    • What type of mutation results from the insertion or deletion of 3 nucleotides (or multiples of 3)?

    <p>Non-frameshift</p> Signup and view all the answers

    What is the term for a mutation that changes the amino acid specified to a stop codon?

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

    What is the term for a base substitution that is a purine to purine or pyrimidine to pyrimidine change?

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

    What type of mutation results from the insertion or deletion of one or more bases to the DNA sequence?

    <p>Insertion, Deletion, and frameshift mutation</p> Signup and view all the answers

    What is the effect of a silent mutation?

    <p>It has no effect on the amino acid sequence.</p> Signup and view all the answers

    What is the primary function of the protein encoded by the CFTR gene?

    <p>Maintenance of the balance of salt and water on cell surfaces</p> Signup and view all the answers

    What is the effect of a nonsense mutation on the resulting protein?

    <p>The protein is shorter than normal and usually nonfunctional</p> Signup and view all the answers

    What type of mutation is the CTT deletion in the CFTR gene?

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

    Why is the loss of the CTT codon (phenylalanine) in the protein sequence of clinical significance?

    <p>It results in a loss of function of the CFTR protein</p> Signup and view all the answers

    What type of mutation is responsible for Cystic fibrosis?

    <p>Frameshift insertion/deletion</p> Signup and view all the answers

    Why was PCR technique used for the detection of the CTT deletion?

    <p>It is a rapid and sensitive method for detecting point mutations</p> Signup and view all the answers

    Which of the following mutations is likely to have a variable effect on the protein function?

    <p>Non-frameshift insertion/deletion</p> Signup and view all the answers

    What is the effect of a point mutation in a regulatory region on protein production?

    <p>The protein is produced in reduced quantities</p> Signup and view all the answers

    What type of mutation is the homozygous mutation in the non-coding region of the β-globin gene?

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

    What type of mutation is responsible for Gaucher disease?

    <p>Frameshift insertion/deletion</p> Signup and view all the answers

    Which of the following is a spontaneous cause of mutations?

    <p>Replication errors during DNA synthesis</p> Signup and view all the answers

    What is the effect of a frameshift insertion/deletion on protein function?

    <p>The protein is nonfunctional and usually shorter than normal</p> Signup and view all the answers

    What is the purpose of PCR genetic analysis in the diagnosis of Cystic fibrosis?

    <p>To detect the deletion of CTT at exon 11 of the CFTR gene</p> Signup and view all the answers

    What is the result of trinucleotide repeat expansion mutation in Huntington's disease?

    <p>An increase in glutamine repeat from 6-35 to 36-121</p> Signup and view all the answers

    What is the mechanism of DNA damage caused by X-Ray?

    <p>Generation of free radical OH that reacts with DNA</p> Signup and view all the answers

    What is the effect of a mutation in a non-coding region on protein production?

    <p>The protein is normal but production is affected</p> Signup and view all the answers

    What is the result of UV light exposure on DNA?

    <p>Formation of pyrimidine dimers between two adjacent Thymine</p> Signup and view all the answers

    What type of mutations are caused by exposure to mutagens?

    <p>Induced mutations</p> Signup and view all the answers

    What is the effect of smoking on DNA?

    <p>Binding of a bulky compound to G, preventing GC base pairing</p> Signup and view all the answers

    Where do somatic mutations occur?

    <p>In somatic cells</p> Signup and view all the answers

    What type of transmission is responsible for inherited diseases?

    <p>Vertical transmission</p> Signup and view all the answers

    What is the primary function of proofreading by DNA Polymerase during DNA replication?

    <p>To repair mismatched bases</p> Signup and view all the answers

    What is the consequence of failing to repair DNA damage?

    <p>Serious consequences to the cell, and potential disease</p> Signup and view all the answers

    What is the frequency of mutations during DNA replication?

    <p>One mispairing per 109 to 1012 nucleotides</p> Signup and view all the answers

    What type of mutations are due to the combined effects of vertical and horizontal transmission?

    <p>Induced mutations</p> Signup and view all the answers

    What is the purpose of DNA repair mechanisms?

    <p>To identify and correct DNA damage</p> Signup and view all the answers

    What is the primary cause of DNA damage?

    <p>Both normal metabolic activities in human cells and environmental factors</p> Signup and view all the answers

    What is the role of enzymes that catalyze repair of mismatched bases during DNA replication?

    <p>To repair mismatched bases</p> Signup and view all the answers

    Study Notes

    Small Mutations: Single Gene Mutations

    • Small mutations can occur in a single gene, resulting in a change in the nucleotide sequence
    • Types of small mutations include:
      • Substitutions (Point mutations): a single base (nucleotide) change
        • Silent: a mutation that does not alter the amino acid specified
        • Missense: a mutation that replaces one amino acid with another
        • Nonsense: a mutation that changes the amino acid specified to a stop codon
      • Insertions, Deletions, and Frameshift mutations: an insertion or deletion of one or more bases to the DNA sequence
        • Non-frameshift: insertion or deletion of 3 nucleotides (or multiples of 3)
        • Frameshift: insertion or deletion of nucleotides other than 3 or multiples of 3

    Effects of Mutations

    • Mutations can occur in:
      • Coding regions of a gene
        • Affect the amino acid sequence of the protein
      • Non-coding regions of a gene
        • Affect protein binding sites, promoter sequences, splice sites, etc.
    • Effects of mutations on protein function:
      • Frameshift insertion/deletion: usually nonfunctional; often shorter than normal
      • Non-frameshift insertion/deletion: possible decrease in function; variable effects
      • Point mutations: do not affect quality of protein, but may affect quantity; affect rate of transcription
    • Examples of genetic disorders caused by mutations:
      • Cystic fibrosis: deletion of CTT in the CFTR gene
      • Sickle cell anemia: non-conservative substitution in the HBB gene
      • Gaucher disease: insertion of a single DNA base prevents production of an enzyme

    Mutation Identification and Repair

    • Causes of mutations:
      • Spontaneous mutations: DNA replication errors, tautomeric shift, DNA polymerase slippage, trinucleotide repeat expansion
      • Induced mutations: exposure to mutagens such as chemicals, UV light, X-rays, and tobacco smoke
    • DNA repair mechanisms:
      • During DNA replication: proofreading by DNA polymerase
      • After completion of replication: repair of mismatched bases and DNA damage
    • Importance of DNA repair: failure of DNA repair can have serious consequences, leading to disease

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    Description

    This quiz covers the different types of small mutations that occur in a single gene, including substitutions, insertions, and deletions. Learn about point mutations and their effects on gene expression.

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