Download Human Genetics Lab

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Human Genetics Lab
Introduction
Most human characteristics are influenced by several or many genes. However, there are several
characteristics which show a change in expression (phenotype) when one gene is varied. Following are
descriptions of some of these characteristics. Keep a record of your phenotype on the cart provided.
When you show a dominant characteristic, it will not be possible to determine whether you are homozygous
or heterozygous for it. We indicate this by a dash for the second gene (Ex.: P-). If the characteristic is a
recessive one, the genotype will be homozygous (Ex.: pp).
Purpose
In this laboratory exercise, we will examine some human genetic traits. We will determine whether we show
the dominant or recessive trait. We will also determine what percentage of our class shows these traits.
Vocabulary: Define these terms before you begin.
Homozygous
Heterozygous
Dominant
Recessive
Genotype
Phenotype
Procedure
1. Read the instructions for each characteristic.
2. Circle the uppercase letter if you show the dominant trait. Circle the lowercase letter if you show the
recessive trait.
3. Copy the class data from the board.
4. Determine the percentage of the class that has the dominant or recessive trait.
Traits
1. Interlocking fingers: When fingers are interlocked, some people will almost invariably place the left
thumb on top of the right thumb and other will place the right over left. Placing left over right is due
to a dominant gene “K.” Placing the right over left is due to a recessive gene “k.”
2. Examine the second (or middle) joint of each finger for hair. If hair is present, circle the letter “H.”
If not hair is present, circle the small letter “h.”
3. Try to roll your tongue up at the edge. If it can be rolled, circle the letter “R.” If it cannot be rolled,
circle “r.”
4. Examine the shape of your hairline at the front of your head. If it looks like a V, circle the letter “V.”
If it is straight, circle “v.”
5. Examine your earlobes. Determine whether or not they are attached directly to the head. If they are,
they are called attached, circle “e.” If they are unattached, circle “E.”
6. Examine your eye color. If your eyes are any color other than blue, circle “B.” If your eyes are blue,
circle “b.”
7. Examine you hair color. If your (natural) color is any color other than blonde, circle the letter “H.”
If your hair is blonde, circle “h.”
8. Examine your hair for any trace of being curly. If your hair is wavy or curly, circle “C.” If your hair is
naturally straight, circle “c.”
9. Do you get terrible headaches? If you get migraines, circle the letter “M.” If you do not get severe
headaches, circle “m.”
10. If you are right handed, circle “R.” If you are left handed, circle “r.”
11. If your eyesight tends to be nearsighted, circle “N.” If your eyesight is normal, circle “n.”
12. If you have any freckles, circle “F.” If you do not have freckles, circle “f.”
13. Some people have a gap between their center upper teeth. Usually a small part of the gum is between
the teeth. Other people’s teeth are close enough to touch each other. If there is a gap, circle “G.” If
there is no space, circle “g.”
14. A dimple is a dent in either the cheek or chin. Circle the “D” if you have dimples and the “d” if you
do not.
15. Bend your thumb back as far as possible. If you can bend your thumb back to almost a 45 degree
angle, you have a hitchhiker’s thumb. This is recessive, circle “h” if you have it. If you do not have it,
circle “H.”
16. A dominant gene causes the last joint of your little finer to bend inward toward the ring finger. Hold
your hands before you with your palms toward you and your little fingers pressed together.
Determine if they run parallel (“b”) or bend away from each other (“B”).
17. If you have pointy ears, you have “Darwin’s Ears” and should circle “E.” If your ears are rounded,
circle “e.”
18. The long palmer muscle lies along the inner part of the forearm and has a tendon extending through
the wrist to the palm of the hand. Absence of this muscle (“L”) is dominant to the presence of it
(“l”). Clench your fist tightly and flex your hand. Now feel the tendons in your wrist. If there are
three tendons, you have the long palmer muscle (“L”). If there are two tendons you do not (“l”).
19. Use “Ss” if your second finder is sorter than your fourth. Use “sl” if your second finger is longer than
your fourth.
Trait
Your Phenotype
Class Phenotype
Percent
1.
Finger
K
k
___K
___k
___K
___k
2.
Finger hair
H
h
___H
___h
___H
___h
3.
Roller
R
r
___R
___r
___R
___r
4.
Widow’s Peak
V
v
___V
___v
___V
___v
5.
Earlobes
E
e
___E
___e
___E
___e
6.
Eye color
B
b
___B
___b
___B
___b
7.
Hair color
H
h
___H
___h
___H
___h
8.
Hair
C
c
___C
___c
___C
___c
9.
Headaches
M
m
___M
___m
___M
___m
10.
R or L Handed
R
r
___R
___r
___R
___r
11.
Eyesight
N
n
___N
___n
___N
___n
12.
Freckles
F
f
___F
___f
___F
___f
13.
Gap
G
g
___G
___g
___G
___g
14.
Dimples
D
d
___D
___d
___D
___d
15.
Hitchhiker’s
H
h
___H
___h
___H
___h
16.
Bent finger
B
b
___B
___b
___B
___b
17.
Darwin’s ear
E
e
___E
___e
___E
___e
18.
Palmer
L
l
___L
___l
___L
___l
19.
Finger
Ss
Sl
___Ss
___Sl
___Ss
___Sl