Breeding Rebops

AIM: How does sexual reproduction create variety?

Today, we are going to investigate the variety that can be produced by meiosis and fertilization. We are going to breed Rebops. These extraordinary creatures live in soda cans. They are so fast, you have probably never seen one, but here is a picture of one (taken with a quick lens):

Chromosomal analysis has determined that Rebops have a haploid (1n) number of 8, and a diploid number (2n) of 16.

INSTRUCTIONS – PRE-LAB:

Look at the “Rebop Decoder Key” below. You will use this to determine the genotypes and phenotypes of your Rebops.

Genes Code For / Rebop Decoder Key / Parts in Model
Genotype / Phenotype
Antennae / AA / 2 antennas / paperclips
Aa / 1 antennae
aa / no antenna
Nose Color / NN / red nose / yellow, red, or orange mini-marshmallows
Nn / orange nose
nn / yellow nose
Eye # / Ee or EE / 2 eyes / thumb tacks
ee / 3 eyes
# Body Segments / BB or Bb / 3 body segments / marshmallows
bb / 2 body segments
Leg Color / LL or Ll / blue legs / red and blue push pins
ll / red legs
Tail Type / TT or Tt / curly tail / pipe cleaner
tt / straight tail
Humps on Back / HH / 3 green humps / green mini-marshmallows
Hh / 2 green humps
hh / 1 green hump
Gender / XX / female / black tail
XY / male / red tail

Q1: Mom and Dad Rebop are Heterozygous for all traits. Write down their genotypes.

Q2: Observe mom and dad Rebop. Use the “Rebop Decoder Key” to describe the phenotype of the following 8 traits: antennae, nose color, eye #, # body segments, leg color, tail type, back humps andgender. WRITE THESE DETAILS IN YOUR LAB BOOK!!!!!

Q3:Why do mom and dad look identical to each other (except for tail color/ gender?)

Q4: What are the total number of gametes that could result from meiosis in mom or dad rebop?

Q5: PREDICT: If these two parents, which are heterozygous for all genes, breed, will their offspring be identical (in either genotype of phenotype) to them? Explain.

Scientists use models for many reasons; one of these is to simulate processes that happen in nature. Today, you will be using a model to simulate breeding Rebops to see how sexual reproduction leads to variety. Before we start the lab, we need to figure out WHY we are doing what are doing in the lab. In other words, what do the steps mean in “real life”

First read through the steps.

Q6: Fill out the “Rebob Model: Parts and Concepts” table that you have taped into your lab notebook that says “Steps in Procedure” and “Concept Modeled by Part or Step.”

eggfertilizationmeiosisspermzygote

You need to say HOW these parts of the procedure are related to what happens to a cell in real life(listed above) and WHY you picked these terms. You must complete this step before you build your baby and get mom and dad’s chromosomes from your teacher.

Step One: Get two bags – MOM and DAD. These bags represent the diploid chromosome number (2n) in the Rebop species.

Step Two: Pick up the MOM baggie. Pair the strips of paper (chromosomes) face down. There should be 8 total homologous pairs.

Step Three:Randomly pick up one chromosome of each length from MOM, and put it aside. Put the unpicked chromosomes back in the MOM bag. Write the code from MOM in your table where it says “chromosome from mom”

Step Four:Repeat Steps two to three for DAD’s chromosomes. Write the code for DAD where it says “chromosome from DAD”

Step Five:Line up MOM and DAD’s chromosomes side by side by length. Then turn over the baby’s chromosomes, and write the genotype in your table.

Step Six: Look at the Rebop Decoder Key to determine the phenotype for your rebop’s genotype, and go build your baby..

Instructions – After building your baby

  1. Make sure you fill out the table for your baby and Mom and Dad’s Chromosomes.

Q7: How does your baby’s genotype compare or contrast to Mom or Dad’s?

Q8: How does your baby’s phenotype compare or contrast to Mom and Dad’s?

Q9: How did the meiosis that you modeled help make your baby become different from its parents?

Q10: How did fertilization continue to make your baby different from its parents?

  1. Now you will compare your baby to other people’s babies. Look at at LEAST two other groups’ Rebops, and list their genotypes and phenotypes for EACH of the 8 traits. You should make a table to do this.

Q11: How are these three babyrebops that you observed evidence that sexual reproduction creates genetic variety among offspring, even when parents have the same genotype?

Q12: Imagine two populations of organisms: Population A reproduces asexually, through mitosis, and Population B reproduces sexually, through meiosis.

  1. Which population would have more genetic diversity? Why?
  2. Which population (A or B) would have a better chance of surviving a disastrous change in the environment? Why?
  1. Mate your Rebop with another Rebop in the class, and record the phenotype and genotype of the resulting grand-baby compared to its parents AND grandparents. If the parents are heterozygous, flip a coin to determine which chromosomes the new baby would inherit. You should do this in a Table or Pedigree / Family Tree.

Q13: Make a family tree, Pedigree, or table of your rebops. Describe how sexual reproduction leads to variety using the Rebop grandparents, parents, and babies as evidence.

Q14: Write a conclusion for the Lab in which you 1) restate the AIM 2) say how what you did helped meet the AIM. You do not need to write a procedure or materials list for this lab.