“Mad Science” Mini-Lessons

4. Modeling Genetic Inheritance


Mendelian inheritance, genetics, meiosis, expression of traits


Model of mother and father reebop; display of chromosomes of mother and father (heterozygous for all alleles); large genotype → phenotype chart (on flipchart paper, tagboard, or maize sack); envelopes or jumbos for “egg” and “sperm” chromosomes for each student group; colored markers for drawing eyes and noses; labeled baskets or other containers for body parts. length soft wires for tails, toothpicks, painted wooden matches for legs, nails for antennae.

Body part Original material TALULAR material
Antenna Nail or pin Nail or pin
Body segment, head Large marshmallow Small Irish potato
Tail Pipe cleaner Soft wire
Nose Thumb tack Ink spot
Leg Push pin wooden match
Eye Thumb tack Ink spot
Hump Miniature marshmallow Flower seed head
Connector Toothpick Toothpick



Make “egg” and “sperm” genomes by cutting two strips of paper of each length for chromosomes 1–7 for each student group.  For each chromosome, flip a coin to determine which allele is carried, for instance, heads for “A” and tails for “a”.  Write the allele on the chromosome.  Randomly place one chromosome of each length into the “egg” envelope or jumbo and the rest into the “sperm” jumbo.  Place an “X” chromosome into the “egg” jumbo and flip a coin to determine if an “X” or “Y” chromosome goes into the “sperm” jumbo.

Display the mother reebop with her genotype and the father reebop with his genotype in the classroom.  Display the genotype → phenotype chart as well.  Sort the materials for making the reebop bodies by body part and arrange them in the classroom by part so that students can easily select the parts they need.  Set aside a place for the reebop nursery if you don’t want students to keep their reebops with them at the conclusion of the activity.


Open the “egg” and “sperm” envelopes and take out the chromosomes.  Match each egg chromosome to the sperm chromosome of the same length.  Arrange the chromosomes into the karyotype of your baby reebop.  Write down the letters you have obtained for the genome of your baby reebop. For example, if you have one chromosome with the letter A and another chromosome with the letter a, your genotype is Aa.

Use the genotype → phenotype chart to decide what the characteristics (phenotype) of your baby reebop will be based on your genotype description. For example, if is genotype is BB, it will have 3 body segments.

Collect all the materials you need for your baby reebop body parts. For example, for 3 body segments you need 3 Irish potatoes.

Build your baby reebop with the characteristics that its genes determine.  Join the segments with toothpicks.

Put your baby in the reebop nursery with the other newborns!

Questions to consider

Mother Reebop chromosomes

Aa Nn Ee Ll Bb Ll Tt Hh XX

Father Reebop chromosomes

Aa Nn Ee Ll Bb Ll Tt Hh XY

genotype → phenotype chart

Characteristic Genotype/ phenotype code
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 = 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

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Copyright © 2004, Richard Barrans
Revised: 21 December 2016; Maintained by Richard Barrans.
URL: http://www.barransclass.com/madsci/MadSci04_Reebop.html