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Genetic & Heredity - Coggle Diagram
Genetic & Heredity
Genetic
Freckles
Freckles are small, concentrated spots of a skin pigment called melanin. Most fair-skinned, red-haired people have them. Freckles are controlled primarily by the MC1R gene. Freckles show a dominant inheritance pattern: parents who have freckles tend to have children with freckles.
Hairline shape
If your hairline forms a point at the center of the forehead, you have a widow's peak. If not, you have a straight hairline. While some sources say that widow’s peak is a dominant trait controlled by one gene, no scientific study supports this claim. Complicating the question of heritability is the fact that the trait is continuous: some people have just a slight suggestion of a peak.
Handedness
Handedness describes our preference for using either our left or right hand for activities such as writing and throwing a ball. Overall, about 10% of people are left-handed, but the number varies among cultures from 0.5% to 24%.
Dimples
Dimples are small, natural indentations on the cheeks. They can appear on one or both sides, and they often change with age. Some people are born with dimples that disappear when they’re adults; others develop dimples later in childhood.
Curly hair
Round hair follicles make straight hair, flattened or c-shaped hair follicles make curly hair, and oval hair follicles make wavy hair. Hair texture is a continuous trait, meaning that hair can be straight or curly or anywhere in between.
Tongue Rolling
Some people can curl up the sides of their tongue to form a tube shape. In 1940, Alfred Sturtevant observed that about 70% of people of European ancestry could roll their tongues and the remaining 30% could not.
Red/Green Colorblindness
Red-green colorblindness is caused by a single gene located on the X-chromosome. This gene codes for a protein in the eye that detects certain colors of light. When this gene is defective, the eye cannot differentiate between red and green.
Earlobe attachment
If earlobes hang free, they are detached. If they connect directly to the sides of the head, they are attached. Earlobe attachment is a continuous trait: while most earlobes can be neatly categorized as attached or unattached, some are in-between.
Hand Clasping
One study found that 55% of people place their left thumb on top, 45% place their right thumb on top, and 1% have no preference. A study of identical twins concluded that hand clasping has a strong genetic basis (most twins share the trait), but it doesn’t fit a predictable inheritance pattern. It is likely affected by multiple genes as well as environmental factors.
PTC tasting
To about 75% of us, the chemical PTC (phenylthiocarbamide) tastes very bitter. For the other 25%, it is tasteless. The ability to taste PTC is controlled mainly by a single gene that codes for a bitter-taste receptor on the tongue. Different variations, or alleles, of this gene control whether PTC tastes bitter or not.
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“How can probability be used to predict genetic traits?"
With the use of probability, scientists can forecast the development of particular features and identify probable child genotypes within a given population.