Human Inheritance Patterns
Discover the fascinating world of Mendelian traits in humans, from mid-digital hair to earlobe attachment. Uncover how traits like freckles, tongue rolling, widow's peak, facial dimples, and hair curliness are inherited. Explore the genetic basis behind these traits and learn how they manifest through generations. Delve into the dominance and recessiveness of various genetic characteristics, shedding light on the complexity of human genetics and heredity.
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Presentation Transcript
Mendelian Traits in YOU! Mendelian Traits in YOU!
Middigital Hair The presence of mid-digital hair is a dominant condition; therefore those lacking it are homozygous recessive.
Freckles Freckles are controlled primarily by the MC1R gene. Freckles show a dominant inheritance parents who have freckles tend to have children with freckles. Variations, also called alleles, of MC1R control freckle number. pattern: Other genes and the environment influence freckle size, color, and pattern. For example, sun exposure can temporarily freckles to appear. Freckles are small, concentrated spots of a skin pigment called melanin. Most fair-skinned, red- haired people have them. cause more
Tongue Rolling Many sources state that tongue rolling is controlled by a single gene. However, as Sturtevant observed, people can learn to roll their tongue as they get older, suggesting that environmental factors not influence the trait. Consistent with this view, just 70% of identical twins share the trait (if tongue rolling were influenced only by genes, then 100% of identical traits would share the trait). just genes 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.
Widows Peak A distinct downward peak of the frontal hairline Having a widow s peak is a dominant trait. Homozygous recessive individuals possess a straight hairline.
Earlobe Attachment Is your earlobe attached or unattached? Free or unattached earlobe is dominant. The homozygous recessive condition is expressed as a direct attachment of the earlobe to the head.
Facial 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. Dimples are highly heritable, meaning that people who have dimples tend to have children with dimples but not always. Because their inheritance isn't completely predictable, dimples are considered an irregular dominant trait. Having dimples is probably controlled mainly by one gene but also influenced by other genes
Hair Curliness 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. Curly hair is influenced by genes much more than by the environment. While curly hair runs in families people with curly hair tend to have children with curly hair its inheritance patterns are often unpredictable. Multiple genes control hair texture, and different variations in these genes are found in different populations. For instance, curly hair is common in African populations, rare in Asian populations, and in-between in Europeans. Straight hair in Asians is mostly caused by variations in two genes different genes from the ones that influence hair texture in Europeans. And different genetic variations make hair curly in African and European populations.
Hitchhikers Thumb Hyperextensibility of the thumb is recessive. Those who cannot bend at least one thumb backward about 45 degrees are probably carrying the dominant gene. Sorry But no hitchhikers thumb
PTC Tasting Can you taste the bitterness of the PTC paper? People who can taste the bitterness are either homozygous dominant (TT) or heterozygous dominant (Tt). People who cannot taste the bitterness are homozygous recessive.
