Alleles - different forms of the
same gene. Two or more alleles can shape each human trait. Each person receives
two alleles of a gene, one from each parent. This combination is one factor
among many that influences a variety of processes in the body. On chromosome
19, the apolipoprotein E (APOE) gene has three common forms or alleles: e2, e3,
and e4. Thus, the possible combinations in one person are e2/2, e2/3, e2/4,
e3/3, e3/4, or e4/4.
ApoE Gene - a
gene on chromosome 19 involved in making ApoE, a substance that helps carry
cholesterol in the bloodstream. The APOE e4 gene is considered a "risk
factor" gene for AD and appears to influence the age of onset of the
Chromosomes - thread-like
structures in every cell of the human body. Chromosomes carry genes. All
healthy people have 46 chromosomes in 23 pairs. Usually, people receive one
chromosome in each pair from each parent.
Genes - basic units of heredity that
direct almost every aspect of the construction, operation, and repair of living
organisms. Each gene is a set of biochemical instructions that tells a cell how
to assemble one of many different proteins. Each protein has its own highly
specialized role to play in the body.
Genetic Mutations - permanent
changes to genes. Once such change occurs, it can be passed on to children. The
relatively rare, early-onset familial AD is associated with mutations in genes
on chromosomes 1, 14, and 21.
Human Genome - the total
genetic information found on the 23 chromosomes inherited from a parent.
Through research decoding the human genome scientists believe humans have
between 30,000 to 35,000 genes.
Proteins - Cells translate
genetic information into specific proteins. Proteins determine the physical and
chemical characteristics of cells and therefore organisms. Proteins are
essential to all life processes.
WebMD Public Information from the U.S. National Institutes of Health