Question

Experiment 3: Following Chromosomal DNA Movement through Meiosis

In this experiment, you will follow the movement of the chromosomes through meiosis I and II to create gametes

Materials 2 Sets of Different Colored Pop-it® Beads (32 of each - these may be any color) 4 5-Holed Pop-it® Beads (used as centromeres)

Procedure
Trial 1

As prophase I begins, the replicated chromosomes coil and condense...

1. Build a pair of replicated, homologous chromosomes. 10 beads should be used to create each individual sister chromatid (20 beads per chromosome pair). The five-holed bead represents the centromere. To do this...

   1. For example, suppose you start with 20 red beads to create your first sister chromatid pair. Five beads must be snapped together for each of the four different strands. Two strands create the first chromatid, and

   2. 1. two strands create the second chromatid.

      2. Place the five-holed bead flat on a work surface with the node positioned up. Then, snap each of the four strands into the bead to create an “X” shaped pair of sister chromosomes.

      3. Repeat this process using 20 new beads (of a different color) to create the second sister chromatid pair. See Figure 4 (located in Experiment 2) for reference.

   3. Assemble a second pair of replicated sister chromatids; this time using 12 beads, instead of 20, per pair (six beads per each complete sister chromatid strand). Snap each of the four pieces into a new five-holed bead to complete the set up. See Figure 5 (located in Experiment 2) for reference.

   4. Pair up the homologous chromosome pairs created in Step 1 and 2. DO NOT SIMULATE CROSSING OVER IN THIS TRIAL. You will simulate crossing over in Trial 2.

   5. Configure the chromosomes as they would appear in each of the stages of meiotic division (prophase I and II, metaphase I and II, anaphase I and II, telophase I and II, and cytokinesis).

   6. Trial 1 - Meiotic Division Beads Diagram

      Prophase I
      
      
      
      Metaphase I
      
      
      
      Anaphase I
      
      
      
      Telophase I
      
      
      
      Prophase II
      
      
      
      Metaphase II
      
      
      
      Anaphase II

      Telophase II
      
      
      
      Cytokinesis

      Trial 2

   7. Build a pair of replicated, homologous chromosomes. 10 beads should be used to create each individual sister chromatid (20 beads per chromosome pair). The five-holed bead represents the centromere. To do this...

      1. For example, suppose you start with 20 red beads to create your first sister chromatid pair. Five beads must be snapped together for each of the four different strands. Two strands create the first chromatid, and two strands create the second chromatid.

      2. Place the five-holed bead flat on a work surface with the node positioned up. Then, snap each of the four strands into the bead to create an “X” shaped pair of sister chromosomes.

      3. Repeat this process using 20 new beads (of a different color) to create the second sister chromatid pair. See Figure 4 (located in Experiment 2) for reference.

   8. Assemble a second pair of replicated sister chromatids; this time using 12 beads, instead of 20, per pair (six beads per each complete sister chromatid strand). Snap each of the four pieces into a new five-holed bead to complete the set up. See Figure 5 (located in Experiment 2) for reference.

   9. Pair up the homologous chromosomes created in Step 6 and 7.

   10. SIMULATE CROSSING OVER. To do this, bring the two homologous pairs of sister chromatids together (creating the chiasma) and exchange an equal number of beads between the two. This will result in chromatids of the same original length, there will now be new combinations of chromatid colors.

   11. Configure the chromosomes as they would appear in each of the stages of meiotic division (prophase I and II, metaphase I and II, anaphase I and II, telophase I and II, and cytokinesis).

   12. Diagram the corresponding images for each stage in the section titled “Trial 2 - Meiotic Division Beads Diagram”. Be sure to indicate the number of chromosomes present in each cell for each phase. Also, indicate how the

   13. crossing over affected the genetic content in the gametes from Trial 1 versus Trial 2.

   14. Trial 2 - Meiotic Division Beads Diagram:

       Prophase I
       
       
       
       Metaphase I
       
       
       
       Anaphase I
       
       
       
       Telophase I
       
       
       
       Prophase II
       
       
       
       Metaphase II
       
       
       
       Anaphase II
       
       
       
       Telophase II
       
       
       
       Cytokinesis

   15. Diagram the corresponding images for each stage in the sections titled “Trial 1 - Meiotic Division Beads Diagram”. Be sure to indicate the number of chromosomes present in each cell for each phase.

   16. Disassemble the beads used in Trial 1. You will need to recycle these beads for a second meiosis trial in Steps 7 - 11.

Answer 1

Answer:

• 1. At the end of meiosis I, each of the 2 daughter cells is haploid, but each chromosome consists of 2 non-identical sister chromatids; At the end of meiosis II, each of the 4daughter cells is haploid, with each chromosome consisting of only 1chromatin thread (since the sister chromatids separated during anaphase

II).

• 2. They contain genetic data and information for the cell to operate.
• 3. At the end of meiosis I, both of the resulting daughter cells are haploid. However, the chromosomes are still double-stranded.
• The homologous pairs have already been separated. In humans, this means that the original cell had 23 pairs of chromosomes, and the cells at the end of meiosis I have 23 chromosomes (not pairs), each of which still have 2 sister chromatids.
• At the end of meiosis II, there are a total of 4 daughter cells, each of which is diploid. At this point, the sister chromatids have separated from each other.
• In humans, this means that these gametes each have 23 chromosomes, each of which has 1 chromatid.

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