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Meiosis and Genetics

Magnetic centromeres to model meiosis

Carolina LabSheets™

In this lab, students investigate how the events of meiosis relate to Mendelian genetics. The lab is designed to supplement the Meiosis Activity of our Carolina BioKits ® : Chromosome Simulation.





Needed Materials

Carolina BioKits ® : Chromosome Simulation.

Optional Materials

Small, colored adhesive dots can be used in place of the masking tape from the kit.

Safety

Ensure that students understand and adhere to safe laboratory practices when performing any activity in the classroom or lab. Demonstrate the protocol for correctly using the instruments and materials necessary to complete the activities, and emphasize the importance of proper usage. Use personal protective equipment such as safety glasses or goggles, gloves, and aprons when appropriate. Model proper laboratory safety practices for your students and require them to adhere to all laboratory safety rules.

Procedures

Students may work individually or in groups of two or more.

Before students perform this lab, ensure they have completed the Mitosis and Meiosis Activities of Carolina BioKits® : Chromosome Simulation so that they know how to assemble the chromosome bead models and simulate the events of cell division. They need the Student Guide for the Meiosis Activity on hand to use as a reference.

If students begin this activity immediately after finishing the Meiosis Activity, they can work with the materials they already have; otherwise, they will need to get the following items from the kit:

  • 40 red beads
  • 40 yellow beads
  • 4 magnetic centromeres
  • 4 red plastic centrioles
  • 4 pieces of string, 3 ft each
  • clear adhesive tape
  • masking tape

Optional: Students may combine their groups and simulate a dihybrid cross. This will illustrate independent assortment and will probably bring up the question of what happens to genes on the same chromosome (linkage).


Answer Key to Questions Asked on the Student LabSheet

What Happens to Allele Pairs in Meiosis?


punnett square showing cross between two heterozygote parents

What fraction of the gametes carry allele B?

½ , 50%

What fraction of the gametes carry allele b?

½ , 50%

At what stage of meiosis were alleles B separated from alleles b?

Anaphase 1


How Do Alleles Recombine in Offspring?

From your completed Punnett square, give the following:

The number of combinations that give a homozygous red-eyed fly

1

The number of combinations that give a homozygous brown-eyed fly

1

The number of combinations that give a heterozygous red-eyed fly

2

The number of combinations that give a red-eyed fly

3

The number of combinations that give a brown-eyed fly

1

What is the probability of getting a red-eyed fly from this cross?

3 out of 4, 75%

What is the probability of getting a brown-eyed fly from this cross?

1 out of 4, 25%

What is the expected ratio of red eyes to brown eyes in the F2?

3:1

A student makes this cross and obtains 120 offspring. Of these, approximately how many would you expect to have red eyes?

90

Brown eyes?

30










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