Chromosome mutation

• What are chromosome mutations?

  Changes in the number of chromosomes
• What process causes chromosome mutations?

  Nondisjunction in meiosis
• What is nondisjunction?

  Failure of chromosomes to separate equally
• In which phase does nondisjunction occur?

  Meiosis
• What are the two types of effects caused by nondisjunction?

  Polyploidy and aneuploidy
• What does polyploidy mean?

  Every single chromosome is affected
• What is aneuploidy?

  Change in the number of one chromosome
• What happens to gametes in polyploidy?

  They can become triploid or tetraploid
• What is the result of nondisjunction in meiosis 1 for polyploidy?

  All chromosomes fail to separate equally
• What is the result of meiosis 2 after nondisjunction in polyploidy?

  Diploid gametes are produced
• What happens when a diploid gamete fuses with a haploid gamete?

  It creates a triploid zygote
• Why is polyploidy fatal in humans?

  Zygotes do not develop successfully
• What is the effect of nondisjunction in meiosis 2?

  One gamete may be diploid
• What does n minus 1 indicate in gametes?

  Missing one chromosome
• What does n plus 1 indicate in gametes?

  One additional chromosome present
• What is the result of fertilization with an n plus 1 gamete?

  Diploid zygote with one extra chromosome
• What is the result of fertilization with an n minus 1 gamete?

  Diploid zygote missing one chromosome
• How does nondisjunction in meiosis 2 affect gametes?

  Produces n minus 1 and n plus 1 gametes
• What are the key differences between polyploidy and aneuploidy?

  • Polyploidy:
  • Affects all chromosomes
  • Results in multiple sets of chromosomes
  • Aneuploidy:
  • Affects only one chromosome
  • Results in an extra or missing chromosome
• What are the steps of nondisjunction leading to polyploidy?

  1. Nondisjunction in meiosis 1: all chromosomes fail to separate.
  2. Meiosis 2 occurs normally, leading to diploid gametes.
  3. Diploid gamete fuses with haploid gamete, resulting in triploid zygote.
• What are the steps of nondisjunction leading to aneuploidy?

  1. Nondisjunction in meiosis 1 or 2: one chromosome fails to separate.
  2. Meiosis produces gametes with n minus 1 or n plus 1.
  3. Fertilization leads to zygote with extra or missing chromosome.