DO YOUR EARS HANG LOW?
(EXPLORING HUMAN GENETICS)
Step 1: Determine if you show the dominant or recessive form of each trait below.
Step 2: Use your answer from Step 1 to determine your possible inherited alleles (genotypes) for each trait. Remember: If you are dominant for a particular trait you will write 2 possibilities for your inherited alleles (genotypes). If you are recessive for a trait, you will list only 1 genotype.
TRAIT / DESCRIPTION / Dominant or Recessive? / Inherited Alleles (genotype)EARLOBES / It is a dominant trait to have earlobes that hang down. People that have earlobes attached directly to the side of their head are recessive for this trait.
PINKY / Straight pinky (recessive trait) vs. Bent pinky (dominant trait) Hold your hands together as if you are covering your face. If the tips of the pinkies (or baby fingers) point away from one another, the pinkies are bent.
WIDOW’S PEAK / If you have a hairline like Eddie Munster or a vampire that comes to a point in the middle of your forehead, you possess a dominant allele for widow’s peak. A straight or even hairline indicates you are recessive for this trait.
HITCHHIKER’S THUMB / People who can bend the last joint of their thumb back to a 90-degree angle are dominant for hitchhiker’s thumb. Those who lack this ability are recessive for this trait.
POLYDACTYLY / If you were born with six fingers or toes you possess a dominant trait for polydactyly. Having five fingers and toes is a recessive trait. In the US, people with extra toes and fingers usually have them removed shortly after birth.
TRAIT / DESCRIPTION / Dominant or Recessive? / Inherited Alleles (genotype)
CLEFT CHIN / If you have a chin like John Travolta that has a split in the middle, you have a cleft chin. This is a recessive trait. The absence of a cleft chine is a dominant feature.
HAIR WHORL / Ask a friend to look at the back of your head to determine if your hair whorls to the right (clockwise) or to the left (counterclockwise). If you use hairspray or gels on you hair this may be a hard one to do. Clockwise is dominant over the recessive trait, which is counterclockwise.
MID-DIGIT HAIR / Mid-digit hair (dominant trait) vs. No mid-digit hair (recessive trait) Look for hair only on the finger shown by the white arrow below.