Name:
Human Genetic Traits
Since Mendel's work with pea plants, a number of human traits have been studied for their mode of
inheritance. Over 4000 traits have been identified and cataloged and more are added each year. Below
are a number of easily observed human traits along with their suggested* dominant/recessive
inheritance:
Dominant
Normal Pigmentation
Cleft Chin
Dimples
Straight Thumbs
Free Ear Lobes
Dark Eye Color
Freckles
Right Handedness
Mid-digital Hair
Tasting of certain substances
Tongue Rolling
White Forelock
Widow's Peak
Bent Little Finger
Polydactyly (extra fingers)
Brachydactyly (short fingers)
Syndactyly (conjoined fingers)
Wooly Hair (Caucasians)
Curly Hair
Dark Hair
Non-red Hair
Normal Hearing
Broad Lips
Migraine Headache
Wet Sticky Ear Wax
Recessive
Albinism
Smooth Chin
No Dimples
Hitch-hikers Thumb
Attached Ear Lobes
Light Eye Color
No Freckles
Left Handedness
No Mid-digital Hair
Non-taster
Non-roller
No White Forelock
Straight Hair
Straight Little Finger
Normal Finger Number
Normal Length Number
Separate Fingers
Non-wooly Hair
Straight Hair
Light Hair
Red Hair
Hereditary Deafness
Thin Lips
Normal
Dry Crumbly Ear Wax
* Note - Some of these traits may have more complex inheritance than a simple dominance or
recessiveness. Their mode of inheritance listed here is approximate.
Is There Anyone Like You?
Each person is generally thought to have a unique genotype or combination of genetic traits.
Except for identical twins, no one else has exactly the same combination of genetic traits that you have.
The following exercise will ask you to score yourself for a small number of genetic traits. After you
have learned your traits, compare them to your classmates to see if there is anyone like you.
Use the chart on the next page to rate your characteristics for 20 genetically controlled traits. We
will go through each characteristic as a class so you can understand what is meant by the two forms of
each trait. Decide if you have the dominant or recessive for the trait. Record a D on the evaluation
sheet if you have the dominant, or d if you have the recessive.
Compare your results with several of your classmates. Calculate the percent of similarity that you
share for the 20 genetic traits. For example, if you have 15 of the 20 traits in common, your percent
similarity is 75%.
Percent Similarity:
Person 1
Person 2
Person 3 _____
Questions for your consideration (not to be turned in as a lab report):
1. Who was the person that you had the highest percent similarity with? Were you surprised by
this result? Why or why not?
2. Who was the person that you had the least similarity with? Why do you think that this person
had so few traits in common with you?
3. There are an estimated 4-5 billion humans on our planet. Which individuals would you
expect to have a high similarity with? Why?
4. What do you think would happen to the percent of similarity between you and your classmates
if 100 genetic traits were compared? Explain.
5. Pick two of the traits and determine your parent’s/sibling’s phenotypes. Use this information to
draw pedigrees for these two traits showing the possible genotypes of your parents, yourself, and any
siblings.
Evaluation Sheet
Dominant
Recessive
You
Cleft Chin
Smooth Chin
___________________________
Dimples
No Dimples
___________________________
Dark Eyes
Pale Eyes
___________________________
Free Ear Lobes
Attached Lobes
___________________________
Wet Ear Wax
Dry Ear Wax
___________________________
Freckles
No Freckles
___________________________
Dark Hair
Light Hair
___________________________
Non-Red Hair
Red Hair
___________________________
Hair Curly
Hair Straight
___________________________
Widow's Peak
No Peak
__________________________
Right Handed
Left Handed
___________________________
Right Thumbed
Left Thumbed
___________________________
Right Arm Cross
Left Arm Cross
___________________________
Double-jointed
Normal
___________________________
No Hair
___________________________
Mid-digital Hair*
#1
#2
#3
2nd Finger long** 4th Finger long
___________________________
2nd Toe longer
1st Toe longer
___________________________
Vision Normal
Color Blind
___________________________
Migraines
No Migraines
___________________________
Tongue Roller
Non-Roller
__________________________
* Mid-digital Hair Trait. Look for the presence of hairs on the middle joint of the fingers. Having hairs
on any finger of either hand is dominant. No hairs on any finger is recessive.
** Compare the length of the 2nd and 4th fingers. This is not a true dominant/recessive case, but
score which finger is the longest in the appropriate column.