Download Human Inheritance Lab

Human Inheritance Lab
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Ear lobes (E):
o Free ear lobes- homozygous dominant
o People with attached earlobes are recessive.
Eye color (B):
o Blue- homozygous recessive
o Green/ hazel- heterozygous
o Brown- homozygous dominant
Widow’s Peak (W):
o A hairline that forms a downward point in the middle of the forehead – heterozygous
o A smooth hairline is caused by a recessive genotype.
Tongue roller (T): the ability to roll their tongues into a “U” shape when it is extended.
o Roller- heterozygous
o People with the recessive alleles cannot roll their tongues.
Tongue folder (F): the ability to fold their tongues over while sticking it out.
o Folder- homozygous dominant
o People with the recessive genotype cannot.
Bent Little Finger (L): the end joint of the little finger of each hand bending inward.
o Big bend- homozygous dominant
o Little bend- heterozygous
o Straight little fingers are a result of the recessive genotype.
Place your hands on a flat surface, palms down, and relax. Check to see if the first joints of your
little fingers are bent or straight.
PTC Taster (P): Individuals who can taste the bitter chemical phenylthiocarbamide,
o PTC taster- heterozygous
o Those with the recessive genotype cannot taste it.
Taste the strip of control paper. Then taste the strip of PTC Paper to see if there is a difference
or not.
Mid-Digital Hair (H): Individuals who have hair on the middle joints of their fingers
o Hair- Homozygous dominant
o Those with two recessive alleles do not have hair on the joint.
Red hair (R ):
o Dark hair- homozygous dominant
o Light hair- heterozygous
o Individuals with red hair have the recessive genotype.
Curly hair (C ):
o Curly hair- homozygous dominant
o Wavy hair- heterozygous
o Straight hair- homozygous recessive
Eye lashes (Y):
o Long- homozygous dominant
o Medium- heterozygous
o Short- homozygous recessive
Freckles (K):
o Lots- homozygous dominant
o Some- heterozygous
o None- homozygous recessive
Dimples (D):
o 2- homozygous dominant
o 1- heterozygous
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o None- homozygous recessive
Cleft Chin (M):
o No cleft- homozygous dominant
o Cleft- homozygous recessive
Hitchhiker’s thumb (J): A person that can bend the last joint of the thumb to approximately a 45 degree
angle
o No- homozygous dominant
o Yes- homozygous recessive
Index Finger Length (I): If the index finger is shorter than the ring finger (4th finger next to the pinky)
o Shorter- homozygous dominant
o Same- heterozygous
o Longer- homozygous recessive
Hallux Length (G): Individuals with the big toe shorter in comparison to the second toe
o Shorter- homozygous dominant
o Same- heterozygous
o Longer- homozygous recessive
Left-over-right thumb crossing (Q): When the hands are folded in a natural fashion, the left thumb
crosses the right thumb in a dominant genotype. If reversed, a recessive genotype is present.
o Left-thumb cross- homozygous dominant
o Reverse- homozygous recessive
Trait
Ear lobes
Eye color
Widow’s
peak
Tongue
roller
Tongue
folder
Bent little
finger
PTC taster
Mid-digital
hair
Person 1
genotype
Person 2 Punnett Square
genotype
Genotype
probabilities
Most likely
phenotype
Red hair
Curly hair
Eyelashes
Freckles
Dimples
Cleft chin
Hitchhikers
thumb
Index
finger
length
Hallux
length
Left-overright
Class Discussion
1) If a man does not have Hitchhiker’s thumb, what are the two possible genotypes?
2) If a man is homozygous for Hitchhiker’s thumb and marries a woman with homozygous dominant alleles,
what is the probability of them having children with Hitchhiker’s thumb?
4) Is anyone dominant for every trait? Is anyone recessive for every trait? If not, what does this show about
dominance and recessiveness of traits in people?
5) Two people that look alike have thousands of common traits. How often do you think that genetic twins
(aside from identical twins) exist? Explain your answer.
6) What is the ratio of tongue rollers to non-tongue rollers in the class? What is the frequency (%) of tongue
rollers in the class?
7) What is the ratio of dimples to non-dimples in the class? What is the frequency (%) of dimpled students
in the class? ( # of people with dimples/ total number of people)