Genes influence everything about a person including physical attributes, risk for disease development and behavior patterns.
What are genes?
Genes are stretches of DNA, which is a long chain of molecules called bases.
Why do people look and behave differently from each other?
Because there are many forms of each gene and different people carry different combinations of the different gene forms.. For example one person may be tall, have blue eyes and be allergic to bee stings, but another person is short, has blue eyes and is not allergic to bee stings, while another person is medium height, has brown eyes and is allergic to bee stings, and so on.... You can easily see how many combinations can be made with just these three properties. Genes influence all of these traits and any others that you can think of so there are a huge number of different combinations of all of the possible genes.
What determines which form of the genes an individual will carry?
All of the genes an individual carries are received from their parents. There are two copies of each gene in each cell of every person, one copy is from the mother and one is from the father. However, the form of any given gene that is donated by the mother can be different from the form from the father.
What determines which form of the gene is expressed in the individual?
Some gene forms are DOMINANT which means that they are expressed no matter what form the other gene happens to be. Other genes are RECESSIVE which means that they are expressed only if both copies are of the recessive form. For example, albino is recessive to pigmented. A person will be albino only if they receive the albino form of the gene from both parents. In this case the pigmented form is dominant so if a person gets one copy of the albino gene and one copy of the pigmented form, the person will have normal pigment.
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