What are Genes

Genes are the means by which information is passed from parent to offspring. Each adult human, for example, has 23 pairs of chromosomes, each containing many genes that encode everything from eye color to the way cells in our body use energy.  During reproduction, each parent contributes one chromosome from each of the 23 pairs, so that the offspring is a unique recombination of genes from the two parents.

Some diseases, like Huntington’s disease, are genetically determined, meaning that if one parent has the associated gene, and passes it to an offspring, then the offspring will eventually develop Huntington’s disease.  

Other diseases, like Alzheimer’s disease  and Parkinson’s disease appear to depend partly on several genes.  An individual who inherits one or more of these genes may be more likely to develop these diseases than someone without the disease but other factors like environment and medical history appear to also play a role in determining whether a particular individual will (or will not) develop the diseases.

by Catherine E. Myers. Copyright © 2006 Memory Loss and the Brai