R
- ram
- A male sheep.
- reactive oxygen species
- Radicals derived from oxygen, including singlet oxygen, superoxide, peroxide and hydroxyl radical.
- receptor
- A cellular protein that binds hormones or neurotransmitters and initiates a physiologic response. Some types of receptors are located in the plasma membrane, while others are found within the cytoplasm or nucleus.
- rectum
- The terminal section of the large intestine.
- reduction
- Addition of electrons (or electron density) from an atom, most commonly due to addition of hydrogen or removal of oxygen from a molecule. The opposite of oxidation.
- renal
- Pertaining to the kidneys.
- rennin
- An enzyme secreted into the lumen of the stomach of young animals that coagulates milk. Also known as chymosin.
- restriction endonucleases
- Enzymes from bacteria that recognize and cleave specific sequences of DNA. Widely used in recombinant DNA work.
- restriction enzymes
- A common name for restriction endonucleases
- restriction fragment length polymorphism
- A type of polymorphism or variability in DNA widely used for DNA testing. Based on nucleotide differences that create or abolish cleavage sites for restriction endonucleases.
- restriction mapping
- A technique used to identify the number and order of sites in DNA where restriction enzymes cleave.
- reticulum
- One of the ruminant forestomachs.
- retro
- Suffix meaning behind or backward.
- retroperitoneal
- Behind the peritoneum. The kidneys and adrenal glands are not actually in the peritoneal cavity, but retroperitoneal.
- reverse transcriptase
- An enzyme from retroviruses that copies RNA into DNA, and is also used in recombinant DNA work. Known formally as a RNA-dependent DNA polymerase.
- RFLP
- An acronym for restriction fragment length polymorphism.
- rugae
- Folds or wrinkles. Most commonly applied to the folds in the lining of the stomach. Singular is ruga.
- rumen
- The largest of the ruminant forestomachs.
- ruminant
- A group of animals cloven-hoofed animals that have a multicompartmented stomach adapted to ferment a herbivorous diet. Examples include cattle, sheep, deer and bison.
- rumination
- A behavior in ruminants of regurgiting ingesta from the reticulorumen, followed by remastication and reswallowing; "cud chewing"
Last updated on 10/2/2004