Chromosome mutations

• Chromosome mutations occur due to changes in the number of chromosomes
• Chromosome mutations happen spontaneously during meiosis
• What is the process called that causes chromosome mutations during meiosis?

  Nondisjunction
• Nondisjunction in meiosis 1 occurs when chromosomes do not separate equally
• Nondisjunction in meiosis 2 occurs when chromatids do not separate equally in anaphase
• What are the two main types of effects resulting from nondisjunction?

  Polyploidy and aneuploidy
• Polyploidy occurs when every single chromosome in a set is affected
• Aneuploidy results from a change in the number of one single chromosome
• Match the type of chromosome mutation with its definition:

  Polyploidy ↔️ Change in the whole set of chromosomes

  Aneuploidy ↔️ Change in the number of one chromosome
• What type of gamete is produced if meiosis occurs without chromosome mutations?

  Haploid
• A diploid cell in humans has two copies of every chromosome
• Polyploidy in humans is fatal
• Describe the process of nondisjunction leading to polyploidy in meiosis 1:

  1️⃣ DNA replication occurs in interphase

  2️⃣ Homologous pairs fail to separate in meiosis 1

  3️⃣ All chromosomes move into one cell

  4️⃣ Meiosis 2 proceeds normally

  5️⃣ Two diploid gametes are formed
• What type of gamete is formed when a diploid gamete fertilizes a normal haploid gamete?

  Triploid
• Nondisjunction in meiosis 2 occurs when chromatids fail to separate
• Aneuploidy can result in a zygote with one extra or one too few chromosomes
• What is an example of a genetic condition caused by aneuploidy?

  Down syndrome
• Describe the process of nondisjunction leading to aneuploidy in meiosis 1:

  1️⃣ DNA replication occurs in interphase

  2️⃣ One pair of homologous chromosomes fails to separate in meiosis 1

  3️⃣ Meiosis 2 proceeds normally

  4️⃣ Haploid gametes with one extra or one missing chromosome are formed
• A zygote with 2n + 1 chromosomes is formed when an n + 1 gamete fertilizes a normal n gamete
• Nondisjunction in meiosis 2 can result in gametes with either n + 1 or n - 1 chromosomes
• Down syndrome is caused by three copies of chromosome 21
• What term describes a gamete with one missing chromosome?

  n - 1
• Chromosome mutations are more commonly observed in plants