Modeling Meiosis printable pdf download

Modeling Meiosis with Pop Beads

In this exercise, you will study the process of meiosis using chromosome simulation kits. The diploid cell you

will be modeling is greatly simplified, with only one pair of homologous chromosomes (2n = 2).

Procedure

Constructing Chromosomes

Assemble two strands of yellow beads connected to magnetic centromeres and two strands of red beads

connected to magnetic centromeres. One of the red strands represents the chromosome contribution of the

female parent, and one of the yellow strands represents the chromosome contribution of the male parent.

These two strands represent homologous chromosomes. The second red and yellow strands are to be used as

sister chromatids for each of these chromosomes.

Interphase - Significant Event: DNA Replication

Place one strand of red beads and one strand of yellow beads near the

center of your work area. (Recall that chromosomes at this stage would

exist as diffuse chromatin and not as visible structures.) DNA synthesis

occurs during interphase and each chromosome, originally composed of one

strand, is now made up of two strands, or chromatids, joined together at

the centromere region. Simulate DNA replication by bringing the magnetic

centromere region of the second red strand in contact with the centromere

region of the first red strand. Do the same with its homologue, the yellow

strand.

Meiosis I

Prophase I - Significant Events: Synapsis and Crossing Over

Homologous chromosomes come together and synapse along their entire length. The

pairing (synapsis) of homologous chromosomes represents the first big difference

between mitosis and meiosis. A tetrad, consisting of four chromatids, is formed. Entwine

the two chromosomes to simulate synapsis and then simulate the process of crossing over

by popping the beads apart on a red chromatid, at the fifth bead or “gene,” and doing the

same with a yellow chromatid. Reconnect the red chromatid to the five yellow beads and

reconnect the yellow chromatid to the five red beads. Proceed through prophase I of

meiosis and note how crossing over results in recombination of genetic information.

Metaphase I - Significant Event: Tetrads Align on Equator

The tetrads line up in the center of the cell. Position the chromosomes near

the middle of the cell.

Modified from AP Biology, Exercise 3B, Student Guide from Carolina Biological Supply

Modeling Meiosis