Do You Know...

...that phenotypic traits distinguishes us from one another?

Each individual has a unique genetic make up that distinguished us from each other. Genes played an important role in this uniqueness. People are recognized by their phenotypic traits. The law of dominance and recessiveness explains why people have curly hairs and some have straight, cleft chin and hitchhiker thumb.

According to this rule you only need one copy of a dominant gene in order to see a dominant phenotypic trait, but you need two copies of a recessive gene in order to see a recessive phenotypic trait. In some cases incomplete dominance occurs when the phenotype of the heterozygous individual is intermediate between the phenotype of a homozygous dominant and homozygous recessive individual.

Curly hair and Straight hair

File: : Curly hair is incompletely dominant over straight hair those who have wavy hair are intermediate. Some explanations suggest that hair is curly or straight, depending upon the number of disulfide bonds between hair proteins found in the hair shaft. The greater the number of links, the curlier the hair and the fewer the number of links the straighter the hair.

Attached or detached Earlobe

Fact file: Ear lobes in people may be free hanging or completely attached to the side of the face. Attached earlobe is recessive and detached or free hanging are dominant. If your father has two recessive alleles for ear lobe attachment then he will have attached ear lobes. If your mother has one dominant allele for unattached ear lobes and a recessive allele for attached ear lobes, she will have unattached ear lobes. This is because the dominant allele always wins out.

A Hitchhiker thumb

Fact file: The hitchhiker’s thumb (thumb tip bends backward more than 30 degrees) is dominant to a straight thumb. A hitchhiker thumb is a genetic traits that is capable of bending the joint in the thumb to extremes which may look uncomfortable to people who lack this genetic trait. You may also hear hitchhiker's thumb referred to as “hyperextension of the thumb” in a reference to this. There is no particular advantage or disadvantage of having a hitchhiker's thumb, and it certainly does not predispose people to hitchhiking.

Cleft Chin

Fact file: Cleft chin is a dominant trait; it masks the expression of the gene for the normal chin. The “masked gene” is said to be the recessive gene and normal chin is the dominant trait. Cleft chin is a facial characteristic that looks like a dimple or an indentation to a person’s chin. It is caused by the failure of the lower half of the jaw to fuse together during fetal development. Observe mostly in men than in women.