MEIOSIS, RECOMBINATION & DEVELOPMENT
LAB
Making Reebops: A Model for MEIOSIS
INTRODUCTION
Reebops are imaginary animals that have 16 chromosomes (8 homologous pairs) in their body
cells (somatic cells). Since chromosomes come in pairs, genes do too. A gene can consist of a
variety of different forms, but only TWO forms are ever present in an individual - one from the
father & one from the mother. Both members of the pair contribute to the same feature (or
characteristic), such as eye color. Homologous genes are located in corresponding positions on
homologous chromosomes. If homologous genes are identical (i.e., both dominant OR both
recessive), the gene is said to be homozygous. If homologous genes are different (i.e., one
dominant & one recessive), the gene is said to be heterozygous.
Objectives:
 To examine how characteristics in offspring are inherited
 To illustrate one of the ways in which meiosis is responsible for the tremendous
variation in offspring that exists within every species that undergoes sexual reproduction
In order to achieve these objectives, it's important that you understand what happens during
meiosis to produce gametes (sex cells). Remember, EACH parent can only contribute ONE
homologous chromosome (from the pair) during formation of any one gamete. This results in
gametes that have HALF the normal number of chromosomes present in somatic cells.
MATERIALS (Per Group of 2)
 1 ziplock bag containing Dad Reebop's chromosomes, 1 ziplock bag containing Mom Reebop's
chromosomes
Before starting the procedure, examine the parents (Dad & Mom Reebop) very carefully. Take
note of their features - such as number of body segments, leg color, nose color, etc… Both
parents are heterozygous for all the characteristics listed in the Decoding Key (Table 2) except one Reebop is male and one is female. Use common sense to determine which is which!
METHODS
1. Open each parental ziplock bag and place the cards (chromosomes) face down on the table so
you cannot see the genotypes (letters) on them. Keep the Dad and Mom chromosomes
separate (based on color).
2. Sort EACH set of chromosomes into pairs of the same length (i.e., homologous pairs).
3. Now, randomly take one chromosome from each pair of Dad's chromosomes and place them in
a pile called "Male Gamete." (This simulates meiosis occurring in the testes)
4. Randomly take one chromosome from each pair of Mom's chromosomes and place them in a
pile called "Female Gamete." (This simulates meiosis occurring in the ovaries)
5. Fertilize the female gamete (egg) with the male gamete (sperm) by mixing together the male
& female gamete piles. This forms a NEW pile that can be called "Baby Genes." This pile
represents a zygote.
6. Place the remaining (unused) chromosomes back into their original ziplock bags.
7. Sort out the chromosomes of the "baby" into homologous pairs. Flip them right-side-up.
8. Record the letters (genes) you have obtained for your baby Reebop in Table 1: Genotype &
Phenotype Data. For example, if you have one chromosome with the letter A and another
with the letter a, the genotype is Aa.
9. Use the Decoding Key (Table 2) to decide what characteristics (phenotype) your baby has
inherited based on the genotypic data. For example, if the genotype is BB, your baby will
have 3 body segments.
10. Draw your baby Reebop this will be part of your results.
11. Double check that you have NOT made a mistake (i.e., mutated a part). Have your teacher
initial your fully-assembled baby Reebop.
12. Place your baby in the Reebop Nursery. Have a look at the other Reebop babies present.
Check to see if any of the babies are 100% identical to your baby. Account for any
similarities and/or differences.
RESULTS
TABLE 1: Genotype & Phenotype Data
GENE GENE
CHARACTERISTIC from from GENOTYPE PHENOTYPE
DAD MOM
Antennae
Body Segments
Tail
Nose
Legs
Eyes
Humps
Sex
TABLE 2: Decoding Key
Antennae
AA = 2 Antennae
Aa = 2 Antennae
aa = No Antennae
Body Segments BB = 3 Body segments Bb = 3 Body segments bb = 2 Body segments
Tail
TT = Curly tail
Tt = Curly tail
tt = Straight tail
Nose
NN = Yellow nose
Nn = Green nose
nn = Blue nose
Legs
LL = Purple legs
Ll = Purple legs
ll = Pink legs
Eyes
EE = 2 Eyes
Ee = 2 Eyes
ee = 1 Eye
HH = 2 Humps
Hh = 2 Humps
hh = 1 Hump
XX = Female
XY = Male
Humps
Sex
DISCUSSION
1. The cells that undergo meiosis are known as gametes. These cells have the diploid (2n)
number of chromosomes. What was the diploid number in this activity?
2. What was the haploid (n) number of chromosomes in this activity?
3. How much genetic material (DNA) does each parent contribute to an offspring? _________
4. Are there any Reebop babies in the Nursery that are 100% identical?
7. Given your answer to question 6, why is your answer most likely no?
5. How many total baby Reebop outcomes were possible? Please show the math involved.
(HINT: There were 8 pairs of genes involved. For each gene, there were 2 possible phenotypes except for nose color, in which case there were 3.)
6. Write a couple of sentences explaining how sexual reproduction introduces genetic variation
into offspring. Also, why is genetic variation beneficial for a species' continued survival?
7. Use your Biology book to provide a definition for "recombination."
8. Though NOT illustrated in this lab activity, what role does "crossing over" play in regard to
gamete formation AND recombination?