Examples of Homologous Chromosome Separation in Anaphase I

📚 Quick Study Guide

• 🧬 Homologous Chromosomes: These are chromosome pairs (one from each parent) that are similar in length, gene position, and centromere location.
• 🔄 Anaphase I: A stage in meiosis I where homologous chromosomes separate and move to opposite poles of the cell. This is different from mitosis, where sister chromatids separate.
• ✂️ Key Events:
  • ❌ Homologous chromosomes, previously paired up in metaphase I, are pulled apart.
  • 🧵 Spindle fibers shorten, drawing the chromosomes towards the poles.
  • 👯 Sister chromatids remain attached at the centromere – this is crucial!
• ⚖️ Importance: This separation ensures that each daughter cell receives one chromosome from each homologous pair, reducing the chromosome number by half.
• 🔢 Chromosome Number: If the original cell is 2n (diploid), each daughter cell after meiosis I will be n (haploid).

🧪 Practice Quiz

1. Which of the following BEST describes what happens to homologous chromosomes during Anaphase I?
   1. A. They split into sister chromatids, which move to opposite poles.
   2. B. They pair up tightly and exchange genetic information.
   3. C. They separate and move to opposite poles.
   4. D. They align along the metaphase plate.
2. What structure pulls the homologous chromosomes apart during Anaphase I?
   1. A. The cell membrane
   2. B. The Golgi apparatus
   3. C. The spindle fibers
   4. D. The nuclear envelope
3. In what phase *prior* to Anaphase I do homologous chromosomes pair up?
   1. A. Anaphase II
   2. B. Prophase I
   3. C. Metaphase II
   4. D. Telophase I
4. What happens to the chromosome number as a result of Anaphase I?
   1. A. It doubles
   2. B. It remains the same
   3. C. It is halved
   4. D. It quadruples
5. Do sister chromatids separate during Anaphase I?
   1. A. Yes, they separate completely.
   2. B. No, they remain attached at the centromere.
   3. C. Only some of them separate.
   4. D. They might separate, depending on the cell type.
6. Anaphase I is a part of which larger cellular process?
   1. A. Mitosis
   2. B. Meiosis I
   3. C. Meiosis II
   4. D. Binary Fission
7. If a cell starts with 20 chromosomes before Meiosis I, how many chromosomes will each daughter cell have after Anaphase I (assuming proper separation)?
   1. A. 40
   2. B. 20
   3. C. 10
   4. D. 5