14
C a radioactive isotope of normal carbon (12C) emitting a weak beta particle. The half-life of 14C is 5,700 years. This radioisotope is extensively used as a tracer in molecular biology.
A, B antigens
Mucopolysaccharides responsible for the ABO blood group system. The A and B antigens reside on the surface of erythrocytes, and differ only in the sugar attached to the penultimate monosaccharide ...
Aapa mires
Fens, sometimes called ‘string bogs’, of circumpolar distribution, found in northern Scandinavia and boreal Canada. They are soligenous mires with ridges arranged roughly normal to the slope, along ...
abacá
(Manila hemp)The strongest of the hard, natural fibres. It is extracted from the pseudostems of Musa textilis (see MUSA), a relative of the edible bananas. Grown mainly in the Philippines, and native ...
abaptation
The process by which an organism is fitted to its environment as a consequence of the characters it inherits, which have been filtered by natural selection in previous environments. Because present ...
abaxial
Of a plant organ, facing away from the axis or main stem (e.g. the lower surface of leaves). Compare adaxial.
ABC transporter
A family of proteins that span the plasma membranes of cells and function to transport specific molecules into or out of the cell. The name is an abbreviation of ATP-Binding Cassette. ABC ...
abdominal fins
1 In fish, pelvic fins located far back on the belly rather than in the thoracic or jugular position.2 Ventral fins located on the abdominal (belly) side of the body.
Abelson leukaemia virus
A replication-defective murine leukaemia virus (A-MuLV), a retrovirus, that requires coinfection of cells with a ‘helper’ virus to proliferate and to cause a rapidly progressive lymphosarcoma (the ...
Abies
(fir; family Pinaceae)A genus of coniferous trees in which the leaves are crowded on the twigs, often approximately in 2 rows; they are needle-like and single, leaving a round, flat scar when they ...
abiogenesis
The origin of living from nonliving matter, as by biopoiesis. See also spontaneous generation.
abiotic factor
Any of the nonliving factors that make up the abiotic environment in which living organisms occur. They include edaphic factors and all the aspects of climate, geology, and atmosphere that may affect ...
ABM paper
Aminobenzyloxy methyl cellulose paper, which when chemically activated, reacts covalently with single-stranded nucleic acids.
abnormal behaviour
Behaviour that occurs as a result of a pathological condition, including anxiety and stress. Abnormal behaviour is sometimes seen in animals in captivity, where it may take the form of stereotyped ...
ABO system
One of the most important human blood group systems. The system is based on the presence or absence of antigens A and B on the surface of red blood cells and antibodies against these in blood serum. ...
abomasum
In Ruminantia, the fourth and final region of the specialized stomach, corresponding to the stomach in other mammals and the zone in which digestion proceeds with the usual mammalian digestive ...
