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.
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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 fertilised 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 grey, green, hazel and blue eyes. Vision also has a genetic basis. Normal vision is dominant to nearsightedness, night blindness and colour 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. Ear lobes 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 characterises a recessive one.
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- 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