Glossary of Terms

- A -

agglutination

the clumping together of red cells in blood as a result of antibodies attaching to antigens on the surface of the cells. This occurs when blood of incompatible types is mixed together outside of the body, as for example during blood typing. When different types of blood come into contact within the body as a result of a mismatched transfusion, the alien red cells usually burst instead of agglutinate.

alleles

alternate forms or varieties of a gene. The alleles for a trait occupy the same locus or position on homologous chromosomes and thus govern the same trait. However, because they are different, their action may result in different expressions of that trait.

amino acids

organic molecules that are building blocks of proteins. There are at 20 different kinds of amino acids in living things. Proteins are composed of different combinations of amino acids assembled in chain-like molecules. Amino acids are primarily composed of carbon, oxygen, hydrogen, and nitrogen.

anemia

weakness, fatigue, and paleness resulting from a deficiency of red blood cells or insufficient amounts of hemoglobin molecules within the red cells.

antibodies

proteins produced by the body to identify and neutralize or destroy alien antigens. Antibodies are involved in the rejection of mismatched blood transfusions and organ transplants. They are also responsible for recognizing and eliminating bacteria and viruses. Antibodies provide a major defense for our bodies against invasion by alien organisms.

antigens

molecules that provide the specific signature or identity to blood or other tissue cells. When alien antigens are introduced into the body, they stimulate the production and mobilization of antibodies. Antigens are found on the surface of blood and other tissue cells as well as bacteria and viruses.

autosomes

any chromosomes other than a sex chromosome.

- B -

bacteria

microscopic simple single celled organisms lacking chlorophyll and a membrane around their nuclei. They reproduce by mitosis. Many species of bacteria are parasites of humans and other animals and plants. Bacteria are classified as members of the Kingdom Monera.

bilirubin

the yellow-red pigment of human bile. Small amounts of it are normally found in blood and urine. At high bilirubin levels, blood and urine change color and the skin becomes yellow or jaundiced. This is one of the symptoms of mismatched blood transfusions and mother-fetus incompatibility in blood type.

- C -

chimera (also spelled chimaera)

an individual who is genetically two people. Fully chimeric individuals are usually the product of two fertilized ova fusing into a single embryo shortly after conception.

codominance

the situation in which two different alleles for a trait are expressed unblended in the phenotype of heterozygous individuals. Neither allele is dominant or recessive, so that both influence the phenotype. Type AB blood is an example. Such traits are said to be codominant.

chromosomes

thread-like, gene-carrying bodies in the cell nucleus. Chromosomes are composed primarily of DNA and protein. They are visible only under magnification during certain stages of cell division. Humans have 46 chromosomes in each somatic cell and 23 in each sex cell.

- D -

DNA (deoxyribonucleic acid )

a large organic molecule that stores the genetic code for the synthesis of proteins. DNA is composed of sugars, phosphates and bases arranged in a double helix shaped molecular structure. Segments of DNA in chromosomes correspond to specific genes.