What Are Mendelian Traits?
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What Are Mendelian Traits?

In earlier studies, some physical attributes of humans were considered Mendelian in nature, but further study suggested they are in fact not. These traits may involve more complex genetic models that usually include more than one gene. Examples are the color of the eyes and hair, and tongue rolling. Gene dominance plays a part in these traits, but information from other genes are also involved.

Gregor Mendel, an Austrian priest, conducted several experiments on peas. Through these experiments, he was able to come up with important generalizations we now know today as Mendel's Principles of Heredity.

Mendelian traits are passed on to the offspring through the recessive pattern of inheritance or through the dominant pattern. The recessive inheritance pattern needs both parents to have the genes, and offspring must inherit a gene from each parent to display the trait. Through the dominant pattern of inheritance, only one copy of the gene needs to be inherited by a child to display the trait. In the case of autosomal genes the child can inherit the gene from either parent.

The list of Mendelian traits in humans is long and includes many examples. Following are a few from the list.

Recessive Patterns

Sometimes parents get surprised that their child has some physical traits that they both do not possess. This usually happen when both of them carry the same recessive genes that they inherited from their own respective parents.

Attached earlobes – Attached earlobe is one best example of a recessive pattern of inheritance.

Hitchhiker's thumb – Hitchhiker's thumb is the ability of the top portion of the thumb to hyperextend, sometimes almost to a 90 degree angle when one is doing a thumbs up sign.

Albinism – Albinism is a condition where an affected individual lacks the pigment melanin in the hair, skin and eyes. Melanin is a substance that provides color to these body parts. Some affected children wear glasses to enhance their vision, and their eyes are often sensitive to sunlight. These children are also advised to avoid exposure to the sun, as they usually get sunburn easily.

Dry earwax – Earwax are waxy substances produced in the ear. It lubricates the ear as well as protects the ear from infections. The dry type of earwax is usually flaky and gray in color.

Through the Dominant Pattern of Inheritance

Widow's peak – A widow's peak is a visible point in the hairline located at the forehead's center.

Short toes and fingers – This condition is often referred to as brackydactyly. Syndromes that may manifest with brackydactyly include Down syndrome and Rubinstein-Taybi syndrome.

More than five fingers and toes – The presence of extra digits on the fingers and toes is a condition known as polydactyly. The additional digit is often composed of tissues, and sometimes contains a bone with no joints.

Wet earwax – Wet earwax appears brownish and moist.

Other examples are dimples in the cheeks, presence of freckles and free earlobe.


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interesting, votes