mkrbmarshmallowmeiosis

Regents Biology Name _____________________

Meiosis Date _________ Per _________

Lab # _______ Marshmallow Meiosis

A reebop is a little marshmallow organism that has 14 chromosomes (7 pairs). It reproduces sexually. Male reebops go through spermatogenesis to make sperm and female reebops go through oogenesis to make eggs. The sperm and eggs each have 7 chromosomes due to meiosis. When fertilization occurs, 7 chromosomes are given by each parent, and the baby reebop has 14 chromosomes. The reebop diploid (2n) number is 14 and the haploid (n) number is 7.

Purpose:

1. To understand the process of meiosis, fertilization, and development

2. To understand the role of alleles in determining traits of an offspring

3. To understand the difference between genotypes and phenotypes

Materials:

large marshmallows small colored marshmallows toothpicks

white pipe stem cleaners red & blue pushpins thumbtacks

paper chromosome set

Procedure:

1. Observe the mommy and daddy reebops that your teacher has provided for you.

A) Describe their physical characteristics.

___________________________________________________________

2. Work in groups of 2 students. Decide who will represent each parent. Remove the paper chromosomes from each envelope. The “father” should lay the blue chromosomes out on the desk from largest to smallest. The “mother” should do the same with the pink chromosomes. You have just created a reebop karyotype. Karyotyping is a technique used to analyze the chromosomes of an individual.

B) How many chromosomes does each parent have? ________

Homologous chromosomes are pairs of chromosomes that are the same size and shape and code for the same characteristics.

C) How many pairs of homologous chromosomes does each parent have? ________

3. Notice the letters on each chromosome (ex. #1 A, a; #2 Q, q). These letters (capitol and lower case) represent alleles. Alleles are different forms of a gene for a specific trait.

D) Why does each reebop have two alleles for a given trait?

___________________________________________________________

4. Turn the chromosomes over so you cannot see them. Keep them in karyotype order (in pairs, largest to smallest).

5. The "father" should arbitrarily take one blue chromosome from each pair and put it in a pile called "sperm."

E) Is the sperm diploid or haploid? ________________

F) What type of cell division makes sperm (mitosis or meiosis)? ___________

6. The "mother" should arbitrarily take one pink chromosome from each pair and put it in a pile called "egg" (or ovum).

G) Is the egg diploid or haploid? ________________

H) What type of cell division makes eggs (mitosis or meiosis)? __________

7. Put the extra chromosomes back into the correct envelope.

8. Now, reebop fertilization can occur. Join the sperm and egg (two piles of chromosomes). A reebop zygote has been formed! Flip the chromosomes over so you can read them and arrange them in karyotype order (in pairs, largest to smallest).

I) How many chromosomes does your zygote have? ________

J) How does this compare to the number that each reebop parent had (question B)? ________

K) Is the zygote diploid or haploid? ________________

L) What has to happen to the zygote for it to develop into a baby reebop?

___________________________________________________________

9. Complete the table 1 below for your baby reebop by analyzing its chromosomes.

Record the letters on the chromosomes under "alleles."
The alleles that the baby reebop inherited are called its genotype. If the baby reebop has two of the same alleles (ex. #1AA or aa) it is pure for that trait. If the baby reebop has two different alleles (ex. #1Aa) it is hybrid for that trait.
Use table 2 to determine the reebops phenotype. The phenotype is the physical characteristic expressed due to the genotype.

Table 1 Baby Reebop

Chromosome	Alleles (letters)	Genotype (pure or hybrid)	Phenotype (physical characteristic)
1	_____ _____
2	_____ _____
3	_____ _____
4	_____ _____
5	_____ _____
6	_____ _____
7	_____ _____

Table 2

Feature	Genotype	Phenotype	Parts used
Antenna	AA	1 antenna	toothpicks
	Aa	2 antenna
	aa	no antenna
Humps	MM	1 green hump	small marshmallows
	Mm	2 green humps
	mm	3 green humps
Nose	QQ	red nose	small marshmallows
	Qq	orange nose
	qq	yellow nose
Tail	TT or Tt	curly tail	white pipe stem cleaner
Tail	tt	straight tail	white pipe stem cleaner
Eyes	EE or Ee	2 eyes	silver tacks
Eyes	ee	3 eyes	silver tacks
Legs	LL or Ll	blue legs	push pins
Legs	ll	red legs	push pins
Body Segments	DD or Dd	3 body segments	large white marshmallows
Body Segments	dd	2 body segments	large white marshmallows

10. Place the pink chromosomes back onto the mother's envelope and blue chromosomes back into the father's envelope.

11. Build your baby reebop based on the phenotypes in table 1. Once assembled, draw a picture of your baby reebop in the space below and complete the reebop birth certificate. Use colored pencils to shade in humps, nose, and legs (if applicable).

Baby's name ___________________________

12. Compare your baby reebop with three of its siblings. Is your reebop the same or different than its siblings? ____________________________________

13. Place your baby reebop in the designated nursery area on top of its birth certificate.

Discussion and Conclusion: Write the answers to the following questions in complete sentences in your lab book.

1. Reebops have a diploid number (2n) of 14. Explain how the diploid chromosome number is maintained from one generation to the next. (In other words, why did the baby reebop have 14 chromosomes instead of 28?)

2. For any given trait, how many alleles does a baby reebop have? Explain why.

3. Each reebop parent was hybrid for each characteristic. What does this mean?

4. Children from the same parents are not exactly the same. Explain why this is true based on the reebop activity.