Webster's New World Medical Dictionary

DNA, recombinant
DNA made up of DNA mole-
cules of different origins, joined together by using
recombinant DNA technology. A recombinant DNA
molecule is constructed (recombined) from seg-
ments from two or more different DNA molecules.
Under certain conditions, a recombinant DNA mol-
ecule can enter a cell and replicate there.
DNA cloning
The use of DNA-manipulation pro-
cedures to produce multiple copies of a single gene
or segment of DNA. See also 
DNA, recombinant.
DNA polymerase
An enzyme that catalyzes
(speeds) the polymerization of DNA. DNA poly-
merase uses preexisting nucleic acid templates and
assembles the DNA from deoxyribonucleotides.
DNA repair
The process by which a cell uses a
series of special enzymes to repair mutations
(changes) in DNA and restore the DNA to its origi-
nal state. The DNA is constantly mutating and being
repaired. This repair process is controlled by spe-
cial genes. A mutation in a DNA repair gene can
cripple the repair process and cause a cascade of
unrepaired mutations in the genome.
DNA repair gene
A gene that is engaged in DNA
repair. When a DNA repair gene is altered, muta-
tions pile up throughout the DNA.
DNA repair pathway
The sequence of steps in
the repair of DNA. Each step is governed by an
enzyme.
DNA replication
A complex process whereby
the “parent” strands of DNA in the double helix are
separated, and each one is copied to produce a new
(daughter) strand. This process is said to be “semi-
conservative” because one strand from each parent
is conserved and remains intact after replication has
taken place.
DNA sequence
The precise ordering of the bases
(A, T, G, C) from which DNA is composed. Base
pairs form naturally only between A and T and
between G and C, so the base sequence of each sin-
gle strand of DNA can be simply deduced from that
of its partner strand. The DNA nucleotide code is in
triplets, such as ATG; the base sequence of ATG’s