Artwork by Maria Rascon

Purpose: To demonstrate the principles of Mendelian genetics and sex determination, including the concepts of allele, phenotype, genotype, dominant, recessive, codominant, homozygous and heterozygous by creating a simulated baby.

Materials: Two pennies, art supplies, paper.

Procedure:

1) Working with a partner, determine the genotype of the baby by flipping pennies. "Mom" flips one penny to choose an allele for her egg and "Dad" flips the other to choose an allele for his sperm. (Note that the gender of the baby is a special case and is determined by dad alone. Boys are XY and girls are XX. Mom can give only an X but dad can give either an X or a Y.)

2) Record the alleles which resulted from the coin flips, and put "sperm and egg" together. (You cannot pick the traits you want; life doesn't work that way!) Write down baby's genotype for each trait in Table 1. Heads represents allele #1 and tails represents allele #2.

3) Record the baby's phenotype in Table 1 by looking up the genotype you got in the Genotype/Phenotype Reference Sheet. Note: Dominant alleles are written with an uppercase letter and recessive alleles are written as lowercase letters. Dominant alleles mask the expression of recessive ones. Co-dominant alleles are written as uppercase letters with a subscript. Co-dominant alleles result in a phenotype that is blended.

4) Repeat steps 1, 2, and 3 for all traits and then draw, color, and name your creation. Remember that you are drawing a baby's face that represents the traits you got - not a child's or an adult's (no tattoos, no mustaches, no piercings, etc., and not too much hair!)

1. Why is the coin flip used to represent the selection of alleles?

2. Define the following terms:

allele-

phenotype-

genotype-

dominant-

recessive-

codominant-

homozygous-

heterozygous-

chromosome-

locus-

gene-

Table 1: Check here indicating whether you are the mom or the dad and fill in the data below.

Mom's Name: ________________

Dad's Name _________________

Baby's Name: ________________

Trait	Heads	Tails	Allele from Mom	Allele from Dad	Genotype	Phenotype
Gender	X	Y	______X______	_____________	_____________	_____________
Face Shape	R	r	_____________	_____________	_____________	_____________
Chin Shape	N	n	_____________	_____________	_____________	_____________
Chin Dimple	A	a	_____________	_____________	_____________	_____________
Freckles	F	f	_____________	_____________	_____________	_____________
Cheek Dimples	D	d	_____________	_____________	_____________	_____________
Lip Thickness	T	t	_____________	_____________	_____________	_____________
Eye Brows	B	b	_____________	_____________	_____________	_____________
Eye Shape	W	w	_____________	_____________	_____________	_____________
Eyelashes	L	l	_____________	_____________	_____________	_____________
Ear Shape	R	r	_____________	_____________	_____________	_____________
Ear Lobes	F	f	_____________	_____________	_____________	_____________
Widow's Peak	W	w	_____________	_____________	_____________	_____________
Hair Curliness	C1	C2	_____________	_____________	_____________	_____________
Eyebrow Color	D1	D2	_____________	_____________	_____________	_____________
Eye Width	W1	W2	_____________	_____________	_____________	_____________
Eye Size	S1	S2	_____________	_____________	_____________	_____________
Mouth Size	M1	M2	_____________	_____________	_____________	_____________
Nose Size	P1	P2	_____________	_____________	_____________	_____________
Birth Mark	B1	B2	_____________	_____________	_____________	_____________
Skin Tone	S1	S2	_____________	_____________	_____________	_____________
Polygenic Trait	(4 coin flips)		Alleles from Mom	Alleles from Dad	Genotype	Phenotype
Hair Color	A, B	a, b	#1____ #2____	#1____ #2____	__ __ /__ __	_____________
Eye Color	A, B	a, b	#1____ #2____	#1____ #2____	__ __ /__ __	_____________

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Genotype/Phenotype Reference Sheet

Trait	Genotype/Phenotype (Homozygous for Allele 1)	Genotype/Phenotype (Heterozygous)	Genotype/Phenotype (Homozygous for Allele #2)
Face Shape	RR Round	Rr Round	rr Square
Chin Shape	NN Noticeable	Nn Noticeable	nn Less Noticeable
Chin Dimple	AA Absent	Aa Absent	aa Present
Freckles	FF Present	Ff Present	ff Absent
Cheek Dimples	DD Present	Dd Present	dd Absent
Lip Thickness	TT Thick	Tt Thick	tt Thin
Eye Brows	BB Bushy	Bb Bushy	bb Fine
Eye Shape	WW Wide	Ww Wide	ww Round
Eyelashes	LL Long	Ll Long	ll Short
Ear Shape	RR Long	Rr Long	rr Round
Ear Lobes	FF Free	Ff Free	ff Attached
Widow's Peak	WW Present	Ww Present	ww Absent
Hair Curliness	C1C1 Curly	C1C2 Wavy	C2C2 Straight
Eyebrow Color	D1D1 Darker than hair	D1D2 Same as hair	D2D2 Lighter than hair
Eye Width	W1W1 Close Together	W1W2 Average	W2W2 Far apart
Eye Size	S1S1 Large	S1S2 Medium	S2S2 Small
Mouth Size	M1M1 Wide	M1M2 Medium	M2M2 Narrow
Nose Size	P1P1 Small	P1P2 Medium	P2P2 Large
Birth Mark (mole)	B1B1 Left cheek	B1B2 Absent	B2B2 Right cheek
Skin Tone	S1S1 Light	S1S2 Medium	S2S2 Dark
Hair Color	AABB=Black AaBB=Dark Brown aaBB=Blond AABb=Black AaBb=Light Brown aaBb=Blond AAbb=Red Aabb=Dark Blond aabb=white (albino)
Eye Color	AABB=Deep Brown AaBB=Greenish Brown aaBB=Green AABb=Deep Brown AaBb=Light Brown aaBb=Light Blue AAbb=Brown Aabb=Gray-Blue aabb=Pink