New researchout of the University of Pennsylvania reveals yet another fascinating aspect of gene expression regulation. In the higher species genes are not one continuous DNA segment. Instead there are intervening segments within genes known as introns (intervening regions). Many introns are quite long and some are short. After a gene is copied by the transcription machinery (known as RNA polymerase), resulting in an mRNA transcript, these major and minor introns are spliced out of the mRNA by the major and minor spliceosomes, respectively. The new research shows that the minor spliceosomes can be turned off, thus turning off the expression of that gene. Read more