Glossary of Terms

Alleles - Different forms of the same gene.

Base - One of the four different chemical units which comprise DNA. The sequence of DNA bases codes for the amino acid sequence of proteins. These four bases are: adenine, cytosine, guanine, thymine, in DNA and RNA, uracil substitutes for thymine.

Biotechnology - The development of a product or products using biological agents.

Chromosomes - Tiny thread-like structures inside each cell. Chromosomes carry the genes.

Co-dominance - A circumstance where the two alleles (or genes) for a specific trait are equally strong: a mixture of the two phenotypes results: An example is pink snapdragons develop from a red and white cross.

Crossing Over - The process in which genes are exchanged between two chromosomes.

DNA (deoxyribonucleic acid) - The substance within the chromosomes that carries the hereditary instructions for producing proteins and RNA's.

Dominant - A gene or allele that is expressed or "shown" in the phenotype. Dominant genes mask or "hide" recessive genes.

Genes - Tiny biochemical structures inside each cell that determine particular hereditary traits, such as eye color and blood type. Each gene is a segment of DNA that carries instructions for producing the chainlike molecules that make up proteins.

Gene expression - The process by which a cell makes a protein from RNA according to the instructions carried by a gene.

Genetic variation - Refers to the differences in inherited traits that exist among the members of a species.

Genetics - The scientific study of heredity.

Genome - A set of all the genes a species has on its chromosomes. The human genome consists of 50,000 to 100,000 genes.

Genotype - The underlying genetic makeup of a trait or the overall genetic makeup of an individual. It is the two genes an individual carries for a trait.

Heredity - The passing of genetic traits from parent to offspring.

Heterozygous - Two different alleles for the same trait.

Homozygous - Only one allele is present for a particular trait. Both genes are identical.

Hybrid - An organism that has heterozygous alleles (or genes) for one or more traits.

Meiosis - Reproduction in sex cells where the daughter cells produced have half the number of parent chromosomes.

Mendel, Gregor - So-called "father of modern genetics". Austrian monk who discovered how genetic "factors" were passed down.

Mitosis - Reproduction of non-sex cells where the daughter cells produced have the same number of chromosomes as the parent cells.

Mutation - A change in a gene. It may produce a new trait that can be inherited.

Phenotype - The observable appearance of a trait or the overall appearance of an individual.

Protein - Chemical building blocks in the body made of smaller units called amino acids. Proteins exist in every cell.

Recessive - An allele or gene that is not expressed or "shown" in the phenotype because it is "hidden" by the dominant gene.

RNA (ribonucleic acid) - Similar to DNA, it plays a key role in the production of proteins.

Trait - A physical characteristic, such as hair color