Heredity

HEREDITY

What is heredity

ผลการค้นหารูปภาพสำหรับ heredity

Heredity is the passing on of traits from parents to their offspring; either through asexual reproduction or sexual reproduction, the offspring cells or organisms acquire the genetic information of their parents. Through heredity, variations between individuals can accumulate and cause species to evolve by natural selection. The study of heredity in biology is genetics

 

What is traits

ผลการค้นหารูปภาพสำหรับ traits

 

Identical twins have exactly the same DNA, but they are not exactly alike. Each twin has his or her own personality, talents, likes, and dislikes. There are even diseases that appear in one twin but not the other, including arthritis, diabetes, autism, schizophrenia, cancer, and many others. The differences between identical twins don’t come from DNA—they all come from external factors.

Scientists often study twins to understand how genes and the environment work together to affect traits. They compare traits in identical twins, who have identical DNA, and fraternal twins, who share half their DNA, just like any siblings. If a characteristic appears more frequently in identical twin pairs than in fraternal twin pairs, then it has an inherited component.

 

5 heredity examples

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.

Although some sources say that this trait is controlled by a single gene, with unattached earlobes being dominant over attached earlobes, no published studies support this view. Earlobe attachment and shape are inherited, but it is likely that many genes contribute to this trait. As such, its pattern of inheritance is difficult to

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.

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 just genes—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).

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.

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.

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.

Widow’s peak is likely controlled by genes rather than the environment. But while hairline shape tends to run in families, its pattern of inheritance is usually unpredictable, suggesting that multiple genes are involved.

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