Question

Part 1 Build a pair of replicated, homologous chromosomes. Use ten beads to create each individual sister chromatid (20 beads per chromosome pair). Two five-holed beads represent each centromere. To do this: a. Start with 20 beads of the same color 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, with a 5-holed bead at the center of each chromatid. This creates an “I” shape. b. Connect the “I”-shaped sister chromatids using the 5-holed beads to create an “X” shape c. Repeat this process using 20 new beads (of a different color) to create the second sister chromatid pair. The blue beads represent one pair of sister chromatids and the black beads represent a second pair of sister chromatids. The black and blue pair are homologous. Second set of replicated chromosomes. Part 2 Assemble a second pair of replicated sister chromatids, this time using 12 beads per pair (six beads per each complete sister chromatid strand).

1. In this experiment, how many chromosomes were present when meiosis I started?

2. In this experiment, how many nuclei are present at the end of meiosis II? How many chromosomes are in each?

Answer 1

1. In this experiment when meiosis I started 4 chromosomes were present.

2. At the end of meiosis II 4 nuclei are present. In each daughter cell there are 2 chromosomes. so, in all 8 chromosomes.

In case of Meiosis I, the chromosomes remain in the duplicated state and the number is reduced to half in the last stage of Meiosis I. Meiosis I is a reduction division whreas Meiosis II is an equational division. The number of chromosomes remain the same.