Dictionary

red blood cell See erythrocyte.

red cell See erythrocyte.

red cell count The number of red blood cells in a volume of blood. The normal range varies slightly between laboratories, but is generally in the range of 4.2–5.9 million cells/cmm. Red cell count can be expressed in international units as (4.2–5.9) × 1,012 cells per liter. Also known as erythrocyte count. See also CBC.

red cell distribution width See CBC.

red-green colorblindness A form of colorblindness in which red and green are perceived as being identical. Red-green colorblindness is the most common type of colorblindness. It is inherited in an X-linked recessive manner and affects 6-8 percent of males in the US. Also known as deutan colorblindness, deuteranopia, and Daltonism. See also colorblindness.

reduction division The first cell division in meiosis, the process by which germ cells are formed. In reduction division, the chromosome number is reduced from diploid (46 chromosomes) to haploid (23 chromosomes). Also known as first meiotic division and first meiosis.

reading frame One of the three possible ways to read a nucleotide sequence in DNA, depending on whether reading starts with the first, second, or third base in a triplet.

reading retardation Impaired ability to read. Reading retardation may reflect mental disability, cultural deprivation, or learning disability. See also dyslexia.

reagent A substance that is used to produce a chemical reaction that allows researchers to detect, measure, produce, or change other substances.

rebound The reversal of response upon withdrawal of a stimulus.

rebound effect The production of increased negative symptoms when the effect of a drug has passed or the patient no longer responds to the drug. If a drug produces a rebound effect, the condition it was used to treat may come back even stronger when the drug is discontinued or loses effectiveness.

recalcitrant Stubborn. For example, a recalcitrant case of pneumonia stubbornly resists treatment.