Quantitative genetic theory and methods have not changed much in the past few decades; it is immune to the rapid changes in our understanding of molecular genetics because quantitative genetics focuses on the net influence of genes and environment, regardless of the complex mechanisms by which genes and environment have their effects. One sign of the speed of changes in molecular genetics in the past few years is that it is difficult even to say what a gene is (Gerstein, Bruce, Rozowsky, Zheng, Du et al., 2007). For the past 50 years, the so-called central dogma of molecular biology has been that a gene is a sequence of DNA that is transcribed into messenger RNA (mRNA) which is then translated into amino acid sequences, the building blocks of protein. We now know that there are only about 24,000 of these traditional genes and their protein-coding regions constitute only 2% of the 3 billion bases of DNA. However, nearly all of the several thousand single-gene disorders involve mutations in these coding regions, which appears to support the central dogma that the major output of the genome is protein from these coding regions.
