chapter  4
31 Pages

Classical genetics and the geography of genes


When we talk about mapping genes these days, we tend to think mostly about the mapping that takes place in molecular genetics. Associated with the Human Genome Project, for example, are: genetic maps that use hypervariable sites in the genome as markers to situate genes on chromosomes by relative distance (“genetic distance”); physical maps that locate genes on chromosomes by absolute distance (in units of DNA nucleotides); and the map that identifies each individual nucleotide of a standard genome, sometimes called the “ultimate map.” These kinds of maps have their historical antecedents in mapping techniques developed in Drosophila melanogaster-the genetic linkage maps invented by Alfred Sturtevant in 1913 and the chromosomal maps made possible by T.S. Painter’s discoveries of 1933-34.