Dominant and recessive genes make each one of us different. Our physical characteristics and our susceptibility to diseases depend on a complex weaving of DNA. Whether a trait is dominant or recessive depends on the parts of a gene that are prevalent. Gene traits determine many characteristics, including hair, vision, facial features and our appendages.
The Nature of Dominant and Recessive
The combination of genes expresses itself in the traits of a person. There are 23 pairs of chromosomes in a single cell of a fertilized egg. On each pair of chromosomes, two genes -- one that is dominant and one that is recessive -- are present. The combination determines the trait of a person. Recessive genes only manifest themselves when the other gene is recessive as well. The presence of a dominant gene means a dominate trait will emerge.
Vision has clear-cut differences in dominant and recessive traits. Brown eyes are a dominant trait over gray, green, hazel and blue eyes. Vision also has a genetic basis. Normal vision is dominant to nearsightedness, night blindness and color blindness.
Traits in hair vary depending on a dominant or recessive gene. Dark hair is always dominant to blond and red hair. Curly hair dominates straight. A full head of hair is also more common and dominant while baldness is recessive. A widow's peak hairline dominates a straight hairline.
Facial features are often a blend of dominant and recessive genes from our parents. Dimples dominate smooth cheeks. Earlobes that are detached to the head are also a dominant feature. A Roman nose and broad lips are indications of dominant genes while a straight nose and thin lips represent recessive genes.
There are some dominant genes that do not often express themselves. Extra toes are dominant but are not common. Fingers that lack a joint, extra fingers, fused fingers and short fingers are also dominant. A straight thumb is dominant while a "hitchhiker's" thumb is recessive. A bent little finger illustrates a dominant gene, while a straight little finger characterizes a recessive one.
- Stanford School of Medicine; Ask a Geneticist; Barry Starr; June 2004
- Georgia Highlands College Division of Social and Cultural Studies: Dominant and Recessive Genes
- Southwest Tennessee Community College Department of Natural Sciences: Human Traits: Autosomal
- Teens Health: The Basics on Genes and Gentetic Disorders
- Photo Credit Thomas Northcut/Lifesize/Getty Images
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