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Guided Inquiry • Skills Lab
Chapter 11 Lab Modeling Meiosis Problem
How does meiosis increase genetic variation?

Introduction
Most cells in organisms that reproduce sexually are diploid. They have two sets of chromosomes and two complete sets of genes. Gametes are an exception. Gametes are the cells that combine during sexual reproduction. In animals, these cells are called sperm and eggs. Gametes are haploid cells with only one set of chromosomes. Meiosis is the process in which haploid cells form from diploid cells.
In this lab, you will model the steps in meiosis. You will make drawings of your models. You will also identify points in the process that can lead to greater genetic variation.

Skills Focus
Use Models, Sequence, Draw Conclusions

Materials
• pop beads
• magnetic centromeres
• large sheet of paper
• colored pencils
• scissors

Safety
Do not direct the points of the scissors toward yourself or others. Use the scissors only as instructed.

Pre-Lab Questions
1. Control Variables Why must you use the same number of beads when you construct the second chromosome in Step 1?

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2. Infer Why is the longer chromosome pair used to model crossing-over?

3. Calculate A diploid cell has two pairs of homologous chromosomes. How many different combinations of chromosomes could there be in the gametes?

Procedure
The diploid cell in your model will have two pairs of homologous chromosomes. In order to keep track of the pairs, you will make one pair longer than the other. The beads will represent genes. Use the large sheet of paper to represent the cell.
Part A: Interphase
Just before meiosis begins, the chromosomes are replicated.
1. Use ten beads and a centromere of one color to construct the long chromosome. Use ten beads and a