Gene Regulation for Higher Cells: A Theory
Cell differentiation is based almost certainly on the regulation of gene activity, so that for each state of differentiation a certain set of genes is active in transcription and other genes are inactive. The establishment of this concept (1) has depended on evidence indicating that the cells of an organism generally contain identical genomes (2). Direct support for the idea that regulation of gene activity underlies cell differentiation comes from evidence that much of the genome in higher cell types is inactive (3) and that different ribonucleic acids (RNA) are synthesized in different cell types (4).