Baby Reebops

Observing reproduction and inheritance in Reebopsus imaginarius

In this activity, we will observe meiosis, fertilization, development and birth of a baby Reebop (Reebopsus imaginarius) . Reebops have 16 chromosomes (2n=16) and 8 different traits are controlled by 8 different genes on those chromosomes.

Procedure:

1. You should have two envelopes, each with a set of chromosomes. Take the maternal chromosomes out and use the information in Table 1 to complete Table 2.

Table 1: Allele 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	Tt curly	tt straight
Nose	NN red nose	Nn orange nose	nn yellow nose
Legs	LL blue legs	Ll blue legs	ll red legs
Sex	XX female	Xy male
Eyes	EE 2 eyes	Ee 2 eyes	ee one eye
Humps	HH 1 hump	Hh 1 hump	hh 3 humps

Table 2: Parental genotypes and phenotypes

Trait	Mom’s Genotype	Mom’s Phenotype	Dad’s genotype	Dad’s phenotype
Antennae
Body segments
Tail
Nose
Legs
Sex
Eyes
Humps

2. Do the same for the paternal chromosomes.

3. Now turn the chromosome cards face down, so that you cannot see the genotypes (letters) on them. Line up the chromosomes into Mom Reebop’s chromosomes (pink) and Dad Reebop’s chromosomes (blue).

4. Randomly take one chromosome of each pair from the Mom’s chromosomes and place in the ‘female gamete’ pile. Repeat for each pair of the Dad’s chromosomes and place them in the ‘male gamete’ pile.

a) What process did you just model? How many chromosomes does each gamete have?

5. Now mix the female gamete and male gamete piles to form a ‘baby chromosome’ pile.

b) What process did you just model? How many chromosomes does the zygote have?

6. Put the remaining chromosomes back into the envelopes.

You have now carried out sexual reproduction, whereby half the chromosomes from one parent have been randomly mixed with half from the other parent to make a unique combination. Note that each parent donated half the chromosome number (eight) that the adult cells contain (i.e. 16). Meiosis is responsible for halving the chromosome number in gametes so that when gametes combine at fertilization, the correct number is present in the new individual.

7. Complete Table 3 for your baby Reebop.

Table 3: Baby genotype and phenotype

Trait	Allele from Mom	Allele from Dad	Baby’s Phenotype
Antennae
Body segments
Tail
Nose
Legs
Sex
Eyes
Humps

c) What kind of inheritance governs nose color? How can you tell? (Hint: Look at the heterozygote)

Sexual reproduction accomplishes a very important purpose and that is to increase diversity.

d) What do you notice about the features that your baby has? Is it identical to either parent?

e) Compare your baby to that of other groups. Are there any babies that are identical?

f) Are any babies the same as their parents?

g) How much genetic material does each parent provide?

h) What are the advantages of increased diversity in a population?