back: Assignments

Human Phenotypes and Genotypes

Number of Chromosomes : 22 autosomal + X + Y
Number of base pairs: approximately 3 billion DNA base pairs
Estimated number of genes: 20,000–25,000 genes.

We are all very close to being the same:
Only about two base pairs in 1000 are different

Two of every type of chromosome.
One from each parent.
Two genes for every trait.
One from each parent.

Genotypes:
People can have two genes of the same type for a trait or two genes of different types for a trait.
Heterozygous – having two genes of the same type for a trait eye color: 2 brown
Homozygous – having two genes of different types for a trait. eye color: one brown and one blue

1. Cleft in the Chin
Absence of a cleft is dominant and may be either homozygous or heterozygous.
The presence of a cleft is recessive and represents a homozygous condition.
Phenotype: Genotype:

2. Hair Curl
Curliness of hair works like incomplete dominance.
Curly is homozygous.
Wavy is heterozygous.
Straight is homozygous.
Phenotype: Genotype:

3. Hairline
A widow’s peak is dominant and may be either homozygous or heterozygous.
A straight hairline is recessive and homozygous.
Phenotype: Genotype:

4. Dimples
Dimples are dominant and homozygous or heterozygous.
Absence of dimples is recessive and homozygous.
Phenotype: Genotype:

5. Earlobes
Definite free earlobes are dominant and homozygous or heterozygous.
Attached earlobes are recessive and homozygous.
Phenotype: Genotype:

6. Freckles on Cheeks
Freckles are dominant and homozygous or heterozygous.
Lack of freckles is recessive and homozygous.
Phenotype: Genotype:

7. Nose
Roman – A nose with a bump is dominant.
Straight – A nose without a bump is recessive.
Phenotype: Genotype:

8. Shape of the face. (Many different genes)
Oval shape is dominant .
Square shape is recessive
Phenotype: Genotype:
To show recessive traits the genotype has to homozygous.
Homozygous means that both alleles for a trait are the same.

9. Eye Color (Two or more genes)
1st Gene (if brown can mask second gen
Brown is dominant over all
Blue is recessive
2nd Gene
Green is dominant
Blue is recessive
Phenotype: Genotype:

10. Hair Color (Two or more genes)
1st Gene (if black can mask other genes)
Dark is dominant
Less Dark is recessive
2nd Gene
Red is dominant
Blond is recessive
Phenotype: Genotype:

11. Hitch-hiker’s Thumb
A thumb that is straight when fully bent back is dominant and is either homozygous or heterozygous.
A thumb in which the segment furthest from the hand forms an angle with the closer segment is recessive and homozygous.
Phenotype: Genotype:

12. Mid-digital Hair
The presence of hair on the back of the middle joint of the fingers is dominant and is either homozygous or heterozygous.
The absence of hair on the back of the middle joint of the fingers is recessive and homozygous.
You will need to look carefully as the hair can be very fine, particularly in women.
Phenotype: Genotype:

13. Eyelash Length
Long eyelashes are dominant and homozygous or heterozygous.
Short eyelashes are recessive and homozygous.
Phenotype: Genotype:

14. Tongue Rolling
The ability to roll the tongue, side edges up, is a dominant trait and is either homozygous or heterozygous.
The inability to roll the tongue is recessive and homozygous
Phenotype: Genotype:

15. Tongue Folding
The ability to fold the tip of the tongue backwards, without touching the roof of the mouth, is recessive and homozygous.
The inability to fold the tongue as described is dominant and is either homozygous or heterozygous.
Phenotype: Genotype:

16. Bent Little Finger
In the dominant condition the center line of the end segment of the little finger bends slightly towards the ring finger. It is either homozygous or heterozygous.
A perfectly straight little finger is recessive and homozygous.
Phenotype: Genotype:

17. Interlaced Fingers
Fold your hands together, interlacing the fingers. Now look at your thumbs.
Left over right is dominant and either homozygous or heterozygous.
Right thumb over left is recessive and homozygous.
Phenotype: Genotype:

18. Index Finger length
The trait for a short index finger is a sex-influenced characteristic which means, in this case, that it is dominant in males and recessive in females. The gene for long index finger is dominant in females.
Phenotype: Genotype:

19. Big Toe Length
The dominant trait is a big toe that is shorter in comparison to the 2nd toe. When the big toe is longer than the 2nd toe, this is a manifestation of the homozygous recessive.
Phenotype: Genotype:

20. Hair on the Back of the Hand
Hair on the back of the hand is dominant and either homozygous or heterozygous.
Hairless hands are recessive and homozygous.
Phenotype: Genotype:

21. Number of the Palmar Tendons
Two tendons in both wrists is dominant. It is either homozygous or heterozygous.
The appearance of a third tendon, even in just one wrist, is recessive and homozygous.
Phenotype: Genotype:
Clench the fist tightly and flex the hand. Feel the tendons in the wrist. You should be able to distinguish two, perhaps even three. Do this for both wrists. One wrist might have two tendons, the other three.

22. Size of Nose (works like incomplete dominance)
Large is more than 38% of face length and homozygous.
Medium is about 1/3 of face length and heterozygous.
Small is less than 31% of face length and homozygous.
Phenotype: Genotype:

23. Size of Ears (works like incomplete dominance)
Large ears are 38% or more of the face length and homozygous.
Medium sized ears are about 1/3 of the face length and heterozygous.
Small ears are 31% or less of face length and homozygous.
Phenotype: Genotype:

24. Width of Mouth (works like incomplete dominance)
A wide mouth is 95% or more of interpupillary distance and is homozygous.
A medium mouth is 70%-90% of interpupillary distance and is heterozygous.
A small mouth is 65% or less of interpupillary distance and is homozygous.
Try not to smile when being measured.
Phenotype: Genotype:

25. Eye Size (Assume incomplete dominance)
Large eyes (>30mm, corner to corner) are homozygous.
Medium eyes (26-30mm, corner to corner) are heterozygous.
Small eyes (<26mm, corner to corner) are homozygous.
Phenotype: Genotype:

26. Reaction Time
One student drops a ruler vertically between the thumb and finger of another student. The second student catches it. Best out of three drops. Record the drop in centimeters.
Phenotype: Genotype:

27. Hand span
Thumb to pinkie finger in centimeters.
Phenotype: Genotype:

28. Blood Types
A is dominant over O
B is dominant over O
A and B are co-dominant
Phenotype: Genotype: