Materials Included In Kit

Additional Materials Required

Prelab Preparation

Part 3. Sno-ball Sillies Genetics Lab Activity

1. Cut out enough sets of the pink (MOM) chromosomes for each student group.
2. Cut out enough sets of the blue (DAD) chromosomes for each student group.
3. Cut each chenille wire (tail) in half. There will be a total of 20 tails available for use.
4. Photocopy enough Sno-ball Sillies—Genetics Simulation Decoder worksheets for each student group to use after they have determined the offsprings’ genotypes.

Safety Precautions

Remind students to use caution when handling sharp pins. Please follow all laboratory safety guidelines.

Disposal

Offspring can be dismantled and all items may be saved for future use or disposed of in the regular trash.

Lab Hints

• Enough materials are provided in this kit for eight groups of four students, with each group making two sno-ball sillies.
• This module can reasonably be completed in four, 50-minute class periods. Complete the POGIL activity on day one, the demonstration on day two, make the sno-ball sillies on day three and collect and compare class data on day four.
• Copying and cutting out extra chromosomes is a good idea in case students lose or misplace chromosomes. This will prevent delay in future class periods. One extra set is provided.

Teacher Tips

• Refer to the POGIL™ frequently as you do the demonstration to get students to make the connections between the two activities.
• Before moving the magnets to each subsequent stage of meiosis, trace the originals with colored chalk or dry erase markers. This will help students visualize what is happening throughout the overall process.
• This activity is ideal as a review of heredity, meiosis, dominant and recessive traits, alleles, chromosomes and Punnett squares.
• The POGIL™ activity is designed to be completed in class using the POGIL™ teaching method. This includes students working in groups with assigned roles to construct their own learning using modeling. For more information, visit www.pogil.org.
• The following activities can be used to further explore meiosis and genetic variation: Mitosis, Meiosis and Cell Division Slide Set (Flinn Catalog No. ML1409) and Allele's Crossing Over to the Other Side Super Value Kit (Flinn Catalog No. FB1792).
• This learning module incorporates the following kits: Magnetic Meiosis Models Biological Demonstration Kit (Flinn Catalog No. FB1992) and Sno-ball Sillies Genetics Simulation Student Laboratory Kit (Flinn Catalog No. FB2199).

Sample Data

Part 3. Sno-ball Sillies Genetics Lab Activity

Answers to Questions

Demonstration

1. In what respect is meiosis II similar to mitosis?

   In both meiosis II and mitosis, sister chromatids separate during anaphase.

2. Compare and contrast what occurs during Prophase I of meiosis and what occurs during Prophase of mitosis. Explain how the processes affect the daughter cells obtained during mitosis vs. meiosis.

   In meiosis, homologous chromosomes form tetrads and exchange alleles during Prophase 1. This does not occur during mitosis. The daughter cells in meiosis are genetically different while the daughter cells in mitosis are genetically identical.

3. Which two events occurring during meiosis contribute to genetic variation?

   During Prophase I, crossing over between homologous chromosomes contributes to genetic variation. Independent assortment of homologous chromosomes during Metaphase I leads to randomization of the two parents’ chromosomes in the resulting daughter cells during Anaphase I.

Post-Lab Questions

1. How many unique offspring were created in the class?

   Data will vary. It is probable that there will be 6 unique offspring.

2. If any two were exactly alike, did their genotypes match also?

   Data will vary. It is unlikely that genotypes and gender will be identical.

3. Compare the offspring to the parents.
   1. Do any of the offspring look exactly like either of the parents?

      Student answers will vary, however, it is unlikely that an offspring will be identical to one parent.

   2. What would happen if it were possible for an offspring to inherit all of its chromosomes from one parent?

      If an offspring inherited all of the chromosomes from one parent, it would be an identical copy or a clone.

4. Choose another team’s offspring to be a mate for your model. Select two of the traits and complete a Punnett square for each.

   Trait: Tail Shape
   Genetic Cross: Tt X Tt

   {11410_Answers_Figure_4}

   Offspring Genotypic Ratio: 1 TT: 2 Tt: 1 tt
   Offspring Phenotypic Ratio: 3 curly: 1 straight
   
   Trait: Body Segments
   Genetic Cross: bb X Bb

   {11410_Answers_Figure_5}

   Offspring Genotypic Ratio: 0 BB: 2 Bb: 2 bb
   Offspring Phenotypic Ratio: 2 two body segments: 2 three body segments or 1:1

5. The following table includes the phenotypes of each parent. Using the class data of offspring, determine the genotypes for each parent’s traits.
   {11410_Answers_Table_2}

   *Correct genotype based on chromosomes.

6. Is it possible for a mating pair of two-eyed Sno-ball Sillies to have offspring with three eyes? Explain your reasoning.

   It is possible. If the two-eyed Sno-ball Sillies are both heterozygous for number of eyes, then even though they both have two eyes, they possess the allele for three eyes; it is just hidden by the dominant allele. If the offspring received the recessive allele from each parent, the offspring would have three eyes.

7. By random selection of one of two alleles for each of the eight traits, how many different varieties of offspring can be created? (Hint: If two forms for a trait exist, the possibilites are 2 x 2 = 4; if three traits exist, the possibilities are 2 x 2 x 2 = 8).

   2⁸ = 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 = 256 different varieties could be created.

8. If none of the offspring had three body segments, what might be inferred about the DAD’s genotype for body segments? Can you be certain?

   It could be inferred that the DAD’s genotype is homozygous dominant (BB); however, it cannot be certain. It is possible the DAD’s genotype is Bb, and the dominant allele was randomly selected for all the offspring.

Post-Lab Analysis

1. Using a claims, evidence and reasoning model, explain how the process of meiosis leads to the patterns of inheritance seen in Mendelian traits.
   1. Propose a claim based in scientific understanding of meiosis and inheritance.

      Meiosis includes two mechanisms that lead to independent inheritance of traits. Crossing over swaps alleles for the same genes between the maternal and paternal chromosomes and independent assortment of maternal and paternal chromosomes during metaphase I ensures that each of the daughter cells will have a random mixture of maternal and paternal chromosomes.

   2. Discuss how the evidence from the simulation and from two real world examples support the claim.

      Student answers will vary. The evidence must match the data collection. For example, if the student claims that meiosis leads to increased genetic variation between offspring from parents with the same genetic make-up, they should use the class data showing this as evidence. Students may discuss the inheritance of sex chromosomes or of specific, Mendelian traits such as cystic fibrosis or Tay-sachs disease.

   3. Discuss the reasoning for the claim based on connections to the POGIL™ activity, the demonstration and the lab activity.

      Student answers will vary. The reasoning should include connections to crossing over and independent assortment as mechanisms that allow for this to occur in the simulation. Students may discuss how the genes are probably on different chromosomes or located far from each other for them to have a high level of independent assortment.

Teacher Handouts

11410_Teacher.pdf

References

Meiosis. POGIL™ Activities for High School Biology. Trout, L., Editor; Flinn Scientific: Batavia, IL (2012).

Introduction

Meiosis is cell division that produces reproductive cells called gametes by reducing the number of chromosomes in the cell by half. It also increases genetic variation between members of a gene pool. In this module, you will explore the process of meiosis and how gametes combine genetic information to pass inherited traits from generation to generation.

Concepts

• Genetic variation
• Crossing over
• Independent assortment
• Genotype vs. phenotype
• Dominant vs. recessive

Background

Part 1. Establishing Background Knowledge

In groups, complete the Meiosis POGIL™ activity.

Part 2. Modeling Meiosis Demonstration

This demonstration breaks down the stages of meiosis. Complete the observations on the Meiosis Worksheet as you view the demonstration, then complete the discussion questions with your group.

Part 3. Sno-ball Sillies Genetics Lab Activity

As a naturalist, a student of natural history, you are studying organisms of the Amazon Rainforest. On an expedition, you discovered a colony of a new species—dubbed the “sno-ball sillies” due to their snow ball-shaped bodies—which has yet to be identified. Wanting to know as much as you can about this new species, you bring a male and female back to your research lab to breed them and learn about their inheritance patterns.

Examining an organism at the cellular level shows that almost all cells have the same number and type of chromosomes. For example, a human body cell has 46 chromosomes. Each chromosome matches up to make a pair that is similar in shape and size. These are called homologous chromosomes and are inherited from the parents. One is inherited from the mother and one is inherited from the father. Each homologous chromosome in a pair carries the same sequence of genes, which encode for traits. However, the version of the gene, called an allele, found on one homologous chromosome does not always match the other. Alleles for the traits studied in this simulation are either dominant or recessive. A genotype represents the alleles contained in the gene of a homologous pair and can only be determined through laboratory testing, whereas a phenotype is the observable characteristic. A dominant phenotype only requires the presence of one allele in order for the trait to be observable, regardless of the other allele present. Recessive phenotypes require the presence of two copies of the same allele. For example, the gene for freckles is on chromosome 16 (see Figure 1a). The alleles present determine whether or not a person has freckles (dominant) or no freckles (recessive). Looking at Figure 1, one chromosome carries the dominant allele (F) for freckles and the other carries the recessive allele (f) for no freckles. In this person, freckles will be seen in the phenotype because the dominant allele hides or masks the recessive allele.

Humans have 23 homologous pairs of chromosomes. In females, all 23 match in size and shape. In males, however, one pair does not match. The two chromosomes that do not match are the X and Y, or sex chromosomes. Not all species follow this pattern. For example, in birds, snakes and some insects, females carry the mismatched chromosome pair while males carry the identical pair. Using these principals of inheritance, you and a partner will create an offspring from a mating pair of the new, unknown species. Then, using the offspring created, you will determine the parents’ genotypes.

Experiment Overview

The purpose of this learning module is to facilitate understanding of the processes involved in producing gametes and how inherited traits are passed to offspring. First, use models in the Meiosis POGIL™ activity to discover how the process of meiosis produces gametes and increases genetic variation. Then, observe the demonstration, which reiterates the processes involved in meiosis. Finally, carry out a lab activity to explore how independent assortment helps create diverse offspring.

Materials

Safety Precautions

Pins are sharp; handle with care. Please follow all laboratory safety guidelines.

Procedure

Part A. Chromosome Sorting

1. Put the pink chromosomes on the lab table with the letters face down.
2. Match the chromosomes as homologous pairs (matching size).
3. Randomly take one chromosome from each homologous pair. Set aside chromosomes NOT chosen.
4. Repeat steps 1–3 with the blue chromosomes.
5. Match the pink “MOM” chromosomes to the homologous blue “DAD” chromosomes (match size).
6. Flip the chromosomes over and fill in the table on the Meiosis Worksheet under Part 3.
7. Obtain a Sno-ball Sillies Genetics Simulation Decoder sheet from your instructor and determine the phenotype of the offspring. Fill in the correct phenotype on the worksheet.

Part B. Offspring Building

1. Using the materials provided, assemble the offspring according to the genotype selected in Part A.
2. Use wooden toothpicks to hold the body segments together and attach the humps. The toothpicks may be broken in half if needed.
3. After the offspring is assembled, draw the offspring on the worksheet. Used colored pencils or label the appropriate color when necessary.

Part 2. Modeling Meiosis Demonstration

Cut the magnetic strip into eight 2" pieces. Draw a cell on the board using chalk or a dry erase marker. This cell should include centrosomes and a nuclear envelope. It should be modified throughout the demonstration to reflect the changes in each stage of meiosis.

Meiosis I

Prophase I

1. Arrange the magnets to represent four chromosomes as shown in Figure 2 for Prophase 1.
   {11410_Procedure_Figure_2}
2. Draw the centrosomes separating to form spindle fibers.
3. Erase portions of the nuclear envelope to display its degradation.

Metaphase I

4. Line up the chromosomes in homologous pairs on the metaphase plate (see Figure 2, Metaphase I).
5. Sketch the centrosomes at opposite poles and the microtubules in between.

Anaphase I

6. Separate the homologous chromosomes towards opposite poles (see Figure 2, Anaphase I).

Telophase I & Cytokinesis

7. Alter the drawing of the surrounding cell to reflect the cleavage furrow beginning to form two separate cells (see Figure 2, Telophase I & Cytokinesis.)

Meiosis II

Prophase II

8. Separate into two cells. Draw spindle fiber formation in each cell (see Figure 3, Prophase II).
   {11410_Procedure_Figure_3}

Metaphase II

9. Align chromosomes along the metaphase plate of each cell (see Figure 3, Metaphase II).
10. Using chalk, include centrosomes, microtubules and kinetochore microtubules.

Anaphase II

11. The centromeres of sister chromatids separate and the chromatids move towards opposite poles (see Figure 3, Anaphase II).

Telophase II & Cytokinesis

12. Using chalk, begin to separate cells by drawing a cleavage furrow (see Figure 3, Telophase II & Cytokinesis).
13. Once the two cells officially separate, haploid daughter cells are formed.

Student Worksheet PDF

11410_Student1.pdf