base
A compound that reacts with an acid to give water (and a salt). A base that dissolves in water to produce hydroxide ions is called an alkali. For example, ammonia reacts as follows:NH3 + H2O ⇌ NH4 + ...
base analogue
A purine or pyrimidine base (see base pair) that differs slightly in structure from the normal base, but that because of its similarity to that base may act as a mutagen when incorporated into DNA. ...
codon
A triplet sequence of nucleotides in messenger-RNA that acts as a coding unit for an amino acid during protein synthesis. It binds by base pairing to a complementary sequence, the anticodon, in ...
complementarity
The concept that a single model may not be adequate to explain all the observations made of atomic or subatomic systems in different experiments. For example, electron diffraction is best explained ...
complementary base sequence
A sequence of polynucleotides related by the base-pairing rules. For example, in DNA a sequence A-G-T in one strand is complementary to T-C-A in the other strand. A given sequence defines the ...
DNA-RNA hybrid
A double helix consisting of one DNA chain and one complementary RNA chain, the two chains being held together by hydrogen bonds between the complementary base pairs.
double helix
The Watson-Crick model of DNA structure, involving plectonemic coiling (q.v.) of two hydrogen-bonded polynucleotide, antiparallel (q.v.) strands wound into a right-handed spiral configuration. See ...
duplex DNA
DNA molecules as described in the Watson-Crick model; that is, with the two polynucleotide chains of opposite 3′-5′ polarity intertwined and annealed.
gigabase
A unit of length for DNA molecules, consisting of one billion nucleotides; abbreviated gb, or gbp for gigabase pairs. The genomes for Homo sapiens and Pisum sativum are 3.2 and 4.1 gigabases, ...
hydrogen bond
A type of electrostatic interaction between electronegative (fluorine, nitrogen, or oxygen) atoms in one molecule and hydrogen atoms bound to electronegative atoms in another molecule. It is a strong ...
long interdispersed element
(LINE)A DNA sequence of more than 5000 base pairs with a copy number greater than 10 000, that occurs throughout the genome rather than in a tandem array.
megabase
Symbol Mb. A unit of length used to measure the size of polynucleotides (i.e. DNA or RNA) or segments of such molecules. 1 Mb = 106 bases or base pairs.
short interdispersed element
(SINE)A DNA sequence, of less than 500 base pairs with a copy number over 100 000, that occurs throughout the genome rather than in a tandem array.
