Genes make people the same and also different. Genes tell your body to make a face with eyes and a nose and mouth, but some people have dark hair, and some people have light hair, and that is also determined by genes. Having light hair or brown eyes, or being tall, all of these are inherited traits.

One of the first people to study inherited traits was a scientist named Felix Mendel. He began an experiment involving pea plants in 1857. He cross-bred two distinct varieties of pea plants and observed the traits of the offspring of a mix of those pea plants. His results showed that the traits he observed in the parent plants were passed on to the offspring in fixed patterns.

Mendel's ideas about the mechanisms responsible for inheritance of traits were the origins of the most important concept in genetics: the gene. Genes are the biological plan for the construction of all living things. They contain all the information the organism needs to construct its body, and to give it some of its unique characteristics. Your body is built according to the plans laid out in your genes. You got your genes from your parents; some from your mother and some from your father. Generally, each gene is responsible for one function. In the human body, which has many complicated systems, many different genes contribute to give the body instructions on how to function.

The major building blocks of genes are deoxyribonucleic acids (DNA). DNA is a very long molecule; if you could see it, it would look like a coiled up ladder. It is made up of the same elements found in our food: sugars, starches, nitrogen, and phosphates. DNA contains messages that the body reads like an instruction book. If you were to unwind one strand of DNA in your body (there are several million), it would stretch more than 5 feet but would be so thin that you couldn't see it.

When a piece of DNA is changed, it is called a mutation. Organisms can be born with mutations or they can be acquired during life from random events or environmental influence.

Mutations can, but don't always, cause genetic diseases. When a person has a genetic disease, that illness is caused by an incorrect message coming from a gene with a mutation. The names of some genetic diseases are Down Syndrome, Turner's Syndrome, and Sickle Cell Anemia. Although AIDS is not a genetic disease, since it is caused by a virus called the Human Immunodeficiency Virus, the virus attacks the body's immune system by working itself into the healthy DNA in the body.

Genetic engineering is the science that looks at taking our knowledge of genes and of DNA and using it to accomplish things like curing genetic diseases, cloning organisms, and changing the genetic code of living things.

Genetic engineers do many things, and one of them is find out what causes genetic diseases and figure out how to fix them. Another genetic engineering project is the international Human Genome Project where scientists are trying to make a map of the genes that make up human beings. The Human Genome Project has led to many discoveries of genes that lead to particular genetic diseases and traits. There are many debates about the ethics of this field of engineering; who does the genetic information belong to: the patients, society, the employers, or the government? Genetic engineers are also developing methods of engineering viruses and other organisms that could be used to manipulate the cells of other living things. Some wonder, though, if this is ethical. Is it going against nature to experiment with these things?

One of the most recent examples of this problem was in the news quite a bit. You may have heard of the cloning of the sheep Dolly. In February of 1998 a Scottish veterinary biologist named Ian Wilmont announced that he was the first person to successfully complete a cloning. By transplanting the DNA from an adult sheep's mammary cell into another sheep's cell, he produced a clone. This announcement was soon followed by many other scientists who claimed to have made other successful clonings. Many now accept that cloning is possible. The question still remains, however, whether cloning has potential uses for humans or whether it is just a dangerous new technology that has more problems than benefits.