This is a review of genetic mapping with molecular markers aimed
at
the non-specialist who wishes to use, or at
least grasp the concepts behind, this powerful analytical tool. Restriction
fragment length polymorphisms
(RFLPs) are defined and used to illustrate the different aspects of mapping.
The
principles of segregation,
recombination and linkage are considered and related to the idea of a molecular
marker map. A description of a
typical mapping population and how it is analysed follows. Traits to be
mapped
are divided into those controlled
by ‘major’ genes and those governed by quantitative trait loci
(QTLs). Exploitation of the map for marker-assisted
selection, gene cloning and synteny comparisons is discussed, as are some
of
the limitations to the usefulness of
molecular marker maps. Finally other marker systems are introduced, namely
minisatellites or variable number
tandem repeats (VNTRs); randomly amplified polymorphic DNA (RAPDs);
microsatellites or simple sequence
repeats (SSRs); and amplified fragment length polymorphisms (AFLPs).