Human Heredity

Biology

What single gene traits do you have?

• Controlled by one dominant or recessive gene

• Does dominant mean the same as most common?

• Is it true that dominant phenotypes are always the most common in a population?

1. Cleft chin - A noticeable indentation at the center of the chin.

– Having a cleft chin is dominant to a smooth chin.

2. Pinky finger – having a bent pinky is dominant to having a straight pinky

3. Hand folding - When the hands are folded either the left or right thumb will be on top.

– Left thumb on top is dominant.

4. Mid-digital hair - Hair growing from the middle section of each finger.

– Hair presence is dominant.

5. Dimples - Round indentations in the cheeks when smiling, not lines or clefts.

– Having dimples is dominant to not

6. Freckles - Small patches of darker pigmented skin on various parts of the body and most visible in those areas commonly exposed to the sun.

– These may be present on both dark and light skinned individuals.

– Freckles are a dominant trait

7. Widow’s peak - the hairline of your forehead.

– A widow's peak is dominant over a straight or curved hairline on the forehead

8. Hair whorling - These may be referred to as cowlicks. Areas in which hair grows from your scalp in a whorl instead of in a given direction.

9. Ear lobes - Free ear lobe is dominant over attached ear lobe

10. Handedness - Right-handedness is dominant over left-handedness

11. PTC tasting – ability taste a certain harmless chemical

– Tasters are less likely to be smokers

– Studies suggest that there may be a link between the ability to taste PTC and preferences for certain types of foods.

12. Tongue rolling - The ability to roll the tongue into a U-shape is dominant over the inability to roll the tongue

13. Big toe length – the big toe is shorter than your second one (dominant trait)

14. Thumb – does it bend back at a 90 angle?

– no hitchhiker’s thumb is dominant to hitchhiker’s thumb

15. Ear wiggling – the ability to wiggle your ears is dominant to not being able to wiggle your ears

• Number of fingers/toes – Polydactyly is having more than five fingers and/or toes – If you have more you have the

dominant condition.– If you have exactly 5 per hand/foot

your phenotype is recessive.

• S-methyl thioester smeller - S-methyl thioesters are produced in the urine after consumption of asparagus. – Some individuals cannot smell this

substance (dominant). – If you smell a strong odor on

urination after eating at least 5 asparagas spears, you are an S-methyl thioester smeller (recessive).

• Darwin tubercle - little bump on the inside of the ear – Having this is dominant to not

having it

• Index finger length – compare your index finger length to your ring finger– In males, a dominant allele causes

the index finger to be shorter than the ring finger

– In females, a dominant allele causes the index finger to be equal to or longer to the ring finger

Multi-factorial• Hair color is determined

by more than one gene• Thus hair color appears to

vary on an almost continuous scale from black to brown to blond to red

• The brown and black pigment is melanin

• The red pigment is an iron containing molecule

• Pigmented irises - When a person is homozygous for the recessive gene (p), there is no pigment in the front part of the eyes and a blue layer at the back of the iris shows through, resulting in blue eyes. – A dominant allele of this gene

(P) causes pigment to be deposited in the front of the iris, thus masking the blue to various degrees.

– A dark iris pigment (green/brown/black) is dominant over the light pigmentation. (gray/blue).