Punnet Square I
Punnet Square II

Punnet Square III
Making Babies

Family Pedigree with Traits
Traits Lab
Mapping Traits
Protein Synthesis

Genetic SLC
DNA Replication

Protein Synthesis
DNA Fingerprinting

Genetics Facts

Student Objectives
Principle of Segregation
Principle of Independent Assortment
In search of the gene.

Heredity Sites

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What Are Your Traits?


  • Fact Sheet


  • Use the Fact Sheet to determine your phenotype.
  • Now think about your parents or brothers and sisters. Write down their phenotypes.
  • If you have your parents phenotypes written down, try to work forward to your own phenotype. See if you can determine your genotype. Remember: you have two genes, one codes for a different trait.



Have you ever wondered why people are so varied in appearance, even when they are closely related? The variation that you can observe exists because there is a huge variety of traits in the human population, and more variation is created each time humans reproduce. This activity will help you understand why even siblings may be quite diverse both phenotypically and genotypically. Congratulations!

The majority of traits, however, have been created to illustrate how human heredity works within a simplified model. Facial characteristics are actually determined in more complex ways than assumed for this activity, and many more than 29 genes are involved.



1. Face shape


2. Chin shape: traits 2, 3 and 4.

Round (RR, Rr)

Square (rr)

Very prominent (V V, V v)

Less prominent (v v)

3. Chin shape: Flip coins for this trait only if trait 2 is genotype V V or V v. The v v genotype prevents the expression of this and the following trait.

4. Chin shape: Flip coins for this trait only if trait 2 was "very prominent:'

Round (RR, Rr)

Square (rr)

Cleft (AA, Aa)

No cleft (aa)


5. Skin color: We will assume that three gene pairs determine skin color. Flip your coins once to determine the genotype of the first pair of genes (AA, Aa, or act). Flip your coins a second time to determine the genotype of the second pair of genes (BB, Bb, or bb). Flip the coins the third time to determine the third gene pair (CC, Cc, cc). Each capital letter represents an active allele for dark pigmentation, so all six capital letters is the darkest skin, and all six small letters is the lightest skin.

6 capital letters—very dark brown, nearly black skin

5 capital letters—dark brown skin

4 capital letters—brown skin

3 capital letters—light brown skin

2 capital letters—tan skin

1 capital letter—light tan/pink skin

0 capital letters—cream, nearly white skin


6. Hair type.





Curly (CC)

Wavy (Cc)

Straight (cc)


7. Widow's peak: down-pointing hairline over center of forehead.





Peak (WW, Ww)

No peak (ww)



8. Eyebrow color: Combine traits 8, 9, and 10 before drawing.




Very dark (HH)

Medium (Hh)

Light (hh)


9. Eyebrow thickness.

10. Eyebrow placement

Bushy (BB, Bb)

Fine (bb)

Separated (NN, Nn)

Connected (nn)

11. Eye color: Eye color determination is similar to skin color determination. Having more active alleles leads to darker eye color. Capital letters are active, and small letters are less active. Assume that one gene pair places pigment in front of the iris, and the second gene pair places pigment in the back of the iris. First throw coins to determine AA, Aa, or aa; then throw coins to determine BB, Bb, or bb. Remember that in reality, the genetic determination of eye color is more complicated than this.

AABB — dark brown

AABb — brown

AaBB — brown

AaBb — brown

Aabb — dark blue

aaBB — dark blue

Aabb — light blue

aabb — pale blue




12. Eye separation.


16. Eyelashes.

Close set (EE)

Middle set (Ee)

Far apart (ee)

Long (LL, Ll)

13. Eye size.




Large (EE)

Medium (Ee)

Small (ee)

Short (ll)

14. Eye shape.


15. Eye angle.


Almond (AA, Aa)

Round (aa)

Horizontal (HH, Hh)

Upward angle (hh)

17. Mouth size: Mouth and lip characteristics are determined in traits 17, 18, 19, and 20.

Long (MM)

Medium (Mm)

Short (mm)

18. Lip thickness.

20. Cheek dimples.

Thicker (LL, Ll)

Thinner (ll)

Dimples (DD, Dd)

No dimples (dd)

19. Lip protrusion (pout).

Very protruding (HH)

Protruding (Hh)

Not protruding (hh)

21. Nose size.





Large (NN)

Medium (Nn)

Small (nn)


23. Nostril flare shape.

22. Nose shape.


Rounded (RR, Rr)

Pointed (rr)

Rounded (RR, Rr)

Pointed (rr)


24. Earlobe attachment.

25. Darwin's earpoint.

Free (FF, Ff)

Attached (ff)

Present (DD. Dd)

Absent (dd)

26. Ear pits.


27. Ear hair: This trait is sex-limited. It is expressed only in males.

Pits (PP, Pp)

No pits (pp)

Less Hairy (HH, Hh)

Very Hairy (hh)

28. Cheek freckles.

29. Forehead freckles.

Freckles (FF, Ff)

No freckles (ff)

Freckles (FF, Ff)

No freckles (ff)