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Questions and Answers

What is a common effect of aneuploidy in humans?

  • Resistance to cancer
  • Increased fertility
  • Spontaneous miscarriages (correct)
  • Enhanced cognitive abilities

    • Which of the following is NOT a way in which mutations can result?

  • DNA copying mistakes during cell division
  • Normal cell differentiation (correct)
  • Exposure to non-ionizing radiation
  • Infection by viruses

    • What is the frequency of genomic mutations that involve changes in chromosomal structure?

  • 1/1000 cell divisions
  • 1/1700 cell divisions (correct)
  • 1/500 cell divisions
  • 1/25-50 cell divisions

    • Which type of mutation is associated with Down syndrome?

    <p>Genomic mutation: aneuploidy</p> Signup and view all the answers

    What is the effect of genomic mutations on fertility?

    <p>Makes reproduction incompatible with life</p> Signup and view all the answers

    What is the primary mechanism of mutations resulting from exposure to ionizing radiation?

    <p>Chromosomal breaks and rearrangements</p> Signup and view all the answers

    What is the definition of polymorphism?

    <p>A variation in the DNA sequence present at a frequency greater than 1 to 3%</p> Signup and view all the answers

    What is the general effect of aneuploidy on cancer cells?

    <p>It is more common in cancer cells</p> Signup and view all the answers

    What is a common location where genetic mutations are found?

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

    What is a consequence of a nonsense mutation?

    <p>A premature stop in translation</p> Signup and view all the answers

    What type of mutation can be caused by both insertions and deletions?

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

    What is a characteristic of synonymous mutations?

    <p>They do not change the amino acid sequence</p> Signup and view all the answers

    What is a result of a mutation in a germline cell?

    <p>The offspring will definitely receive the mutation</p> Signup and view all the answers

    What is a difference between transitions and transversions?

    <p>Transition is a change from one purine to another, while transversion is a change from one purine to one pyrimidine</p> Signup and view all the answers

    What type of mutation occurs when there is a change in a base that does not alter the amino acid sequence?

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

    What is a consequence of a missense mutation?

    <p>A change in the amino acid sequence</p> Signup and view all the answers

    What is the primary difference between a mutation and a polymorphism in terms of disease causality?

    <p>A mutation always causes a disease, while a polymorphism does not</p> Signup and view all the answers

    What type of genetic variation is characterized by variations in the number of copies of long genome segments?

    <p>Polymorphism of the number of copies</p> Signup and view all the answers

    What is a characteristic of genetic diseases related to trinucleotide repeats?

    <p>They are inherited in a Mendelian pattern</p> Signup and view all the answers

    What is true about the affected regions in polymorphisms of the number of copies?

    <p>They are too small to be seen cytogenetically</p> Signup and view all the answers

    What is the main difference between the inheritance pattern of a mutation and a polymorphism?

    <p>Mutations have a clear inheritance pattern, while polymorphisms do not</p> Signup and view all the answers

    What is the primary reason why genetic diseases related to trinucleotide repeats are difficult to diagnose?

    <p>The affected regions are too small to be seen cytogenetically and too long to be sequenced</p> Signup and view all the answers

    Study Notes

    Mutations and Polymorphisms

    • Mutations are rare in population and recent in evolution, while polymorphisms are common in population and old in evolutionary terms.
    • Mutations have a strong effect, while polymorphisms have a weak effect or no effect.

    Origin of Mutations

    • Mutations can result from:
      • DNA copying mistakes during cell division
      • Exposure to ionizing radiation
      • Exposure to chemicals called mutagens
      • Infection by viruses

    Classification of Mutations

    • Genomic mutations:
      • Alterations in the number of intact chromosomes (aneuploidy)
      • Alterations of the structure of individual chromosomes
    • Genetic/Molecular mutations:
      • Alterations in individual genes
      • Substitutions, deletions, and insertions on a small scale

    Genomic Mutations

    • Changes in the number of chromosomes (aneuploidy):
      • Most common mutation in humans (1/25-50 cell divisions)
      • Causes spontaneous miscarriages
      • Common in cancer cells
    • Changes in chromosomal structure:
      • Alteration in the structure of individual chromosomes
      • Involves only part of a chromosome
      • Frequency: 1/1700 cell divisions
      • Generally incompatible with life or normal reproduction
      • Common in cancer cells

    Genetic Mutations

    • Alter individual genes
    • Two basic mechanisms:
      • Errors in DNA replication
      • Mutations in the DNA mismatch repair system

    Classification of Genetic Mutations

    • Substitutions:
      • Can be transitions (change of one purine for another purine) or transversions (change of one purine by one pyrimidine or the opposite)
      • Can be:
        • Missense (change in amino acid sequence)
        • Nonsense (inserts an artificial STOP codon, finishing translation prematurely)
        • Synonymous (change in base but no change in amino acid encoded due to the degeneration of the genetic code)
        • Silent (occurs in a non-coding region)
    • Insertions and deletions:
      • Can cause frameshift mutations
      • Can alter the amino acid sequence

    Inheritance and Consequences

    • Not all mutations have clinical consequences:
      • Silent mutations
      • Synonymous mutations
    • If the mutation occurs in a germline cell, the change will be inheritable
    • If the mutation occurs in a somatic cell, the offspring will not receive it
    • Variations in the number of copies of long genome segments
    • Affected regions are too small to be seen cytogenetically and too long to be sequenced

    Polymorphisms of the Number of Copies

    • Variations in the number of copies of long genome segments
    • Affected regions are too small to be seen cytogenetically and too long to be sequenced

    Comparison of Mutations and Polymorphisms

    • Mutation:
      • Usually causes a disease
      • Follows a Mendelian inheritance pattern
      • Not frequent in population
    • Polymorphism:
      • Causes increased risk, but not direct disease
      • No clear pattern of inheritance
      • Common in population

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