Everyone gets certain traits or characteristics from his parents. Heredity is the passing on of these specific characteristics from one generation to the next. These traits are passed on by genes in our DNA.
DNA is a material found in chromosomes. Chromosomes are located in the nucleus of every cell in the human body. Humans have 23 pairs of chromosomes in each cell. Each child receives one-half of its chromosomes (23) from each parent, for a total of 46. Therefore, each child inherits one-half of its DNA from his father and one-half from his mother.
Pieces of information inside a DNA molecule are called genes. A gene gives instructions about making a certain protein to determine a trait for the person, like color of eyes or hair. A person has a hair color gene, but inside the gene is a specific pattern which makes the hair black, brown or blonde, for example. This is called an allele.
Each child inherits two genes for each trait, like hair color or eye color. Some genes are more dominant than others. That means they win out over the other gene which is called recessive. Brown-eyed genes win out over blue-eyed genes, unless a person inherits two blue-eyes genes, one from each parent. Sometimes genes have codominance, meaning that neither gene is dominant over the other. An example of this is blood type. If one parent has type A and the other has type B, the child will have type AB blood. A trait may not show up in an individual but can still pass on to the next generation.
A mutation Is a change which occurs in a DNA sequence in a chromosome. This change may be due to the effects of smoking, alcohol or other environmental effects or mistakes within the cell itself. The results may be damaging to the body. A mutation can be passed down to a child. Because of certain mutations, diseases can run in families.
The passing down of genetic material from one generation to another can be seen by looking at children and their parents. Many traits can be similar, such as size and shape of nose, hair color, eye color, height or shape of an ear. Sometimes it is easy to spot family traits, and sometimes children don't have many characteristics of their parents at all.
Gregor Mendel is called the father of genetics. His research involved using pea plants of different types. He used smooth, yellow peas and wrinkly green peas. By transferring pollen to and from the flowers of the plants with a small paintbrush, he found out that certain characteristics of the pea plants were dominant and others recessive. From these experiments, Mendel was able to describe the way genetic traits are passed down from parents to children.
In summary, every person inherits certain characteristics from his parents. Heredity is the passing on of these traits. Genes in our DNA are responsible for controlling what traits each person inherits. A child receives two genes for each trait, one from his father and one from his mother. The dominant trait will win out unless the two genes are the same.