Glossary
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Glossary Terms for letter: R
racemization The chemical reaction resulting in the conversion of L amino acids to D amino acids for amino acid dating.
radiocarbon dating The radiometric dating method in which the ratio of 14C to 12C is measured to provide an absolute date for a material younger than 50,000 years.
radioisotopes Elements' unstable, radioactive isotopes.
radiopotassium dating The radiometric dating method in which the ratio of 40K to 40Ar is measured to provide an absolute date for a material older than 200,000 years.
recessive An allele that is expressed in an organism's phenotype if two copies are present, but is masked if the dominant allele is present.
recombination The exchange of genetic material between homologous chromosomes, resulting from a cross-over event.
regulatory genes Those genes that determine when structural genes and other regulatory genes are turned on and off for protein synthesis.
regulatory proteins Proteins involved in the expression of control genes.
replication The process of copying nuclear DNA prior to cell division, so that each new daughter cell receives a complete complement of DNA.
reproductive isolation Any mechanism that prevents two populations from interbreeding and exchanging genetic material.
rhinarium The naked surface around the nostrils, typically wet in mammals.
ribonucleic acid (RNA) A single-stranded molecule involved in protein synthesis, consisting of a phosphate, ribose sugar, and one of four nitrogen bases.
ribosomal RNA (rRNA) A fundamental structural component of a ribosome.
ribosomes The organelles attached to the surface of endoplasmic reticulum, located in the cytoplasm of a cell; they are the site of protein synthesis.
rigidity (bone) Refers to the strength of bone to resist bending and torsion.
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