Genetics is the study of how parents pass some of their characteristics to their children. It is an important part of biology, and gives the basic rules on which evolution acts.

The living things we see around us are made of millions of tiny self-contained components called cells. Inside of each cell are long molecules called DNA. DNA stores information that tells the cells how to create that living thing. Parts of this information that tell how to make one small part or characteristic of the living thing - red hair, or blue eyes, or a tendency to be tall - are known as genes.

Every cell in the same living thing has the same DNA, but only some of it is used in each cell. For instance, genes that tell how to make parts of the liver are not used in the brain. What genes are used can also change over time. For instance, a lot of genes are used by a child early in pregnancy that aren't used later.

A living thing has two copies of each gene, one from its mother, and one from its father. There can be multiple types of each gene, which give different instructions: one version might cause a person to have blue eyes, another might cause them to have brown. These different versions are known as "alleles" of the gene.

Since a living thing has two copies of each gene, it can have two different alleles of it at the same time. Often, one allele will be dominant, meaning that the living thing looks and acts as if it had only that one allele. The unexpressed allele is called recessive. In other cases, you end up with something in between the two possibilities. In that case, the two alleles are called "co-dominant".

Most of the characteristics that you can see in a living thing have multiple genes that influence them. But it's much easier to understand when there's just one gene, so we'll start with that.

Genetic engineering, or GE, is a branch of biology. It focuses on making food, animals and plants better adapted to the need of humans. It does this by tweaking genes. Some people see a problem in this.

There is a risk that some genetically modified (GM) organism is better adapted to some niche in nature, and will take away some space of another organism. It could also be that some of the genetic modifications leak into unengineered plants. Many people do not think so, however. They feel the risks do not outweigh the benefits of GE.

Common genetic modifications are that some plants produce pesticides and fungicides themselves, or that they spoil only later on. Genetic engineering is also used to clone animals. The process of genetic engineering is a common topic of debate among scientists and scholars alike.

For More Information: Genetics, Genetic Engineering

Source: Wikipedia (All text is available under the terms of the GNU Free Documentation License)