Chapter 18 Regulation of Gene Expression Dr. Joseph Silver

In this chapter we will learn about the operon concept non coding RNAs cytoplasmic determinants (induction & determination) polarity determination cancer

see fig operon = a series of enzymes needed to make a protein are next to each other on a chromosome – made up of a promoter which is in the on position and regulatory genes which can turn stop the operon from functioning there are many variations of this concept as well as different ways to regulate the activity of the operon see fig & for more complex versions of operons

non coding RNAs - thought to be regulatory RNAs - ncRNAs (regulation) - miRNAs (degrades or blocks mRNA) - siRNAs (degrade or block mRNAs) - piwi interacting RNAs (change euchromatin to heterochromatin) scientists have discovered thousands of non coding RNAs and for many their regulatory function is still unknown

cytoplasmic determination these are chemicals which appear early in embryonic development and determine the fate of cells induction – interaction between neighboring cells causes cell to go down a specific path determination – secretion of tissue specific proteins determine the fate of the cell

polarity determination - each organisms body has a specific body pattern - cytoplasmic factors provide positional information through induction and determination factors see fig ncRNAs are involved in positional determination

Cancer what is cancer? - mutations of genes causing loss of cell cycle control - proto oncogenes control normal cell cycle - mutated proto oncogenes become cancer causing oncogens

P53 gene = tumor suppressor gene mutated p53 found in more than 50% of cancers p53 has many regulatory functions (guardian angel of the genome) mutated p53 allows increased cell division

ras gene a G protein (RTK transduction) normal function controls cell division rate mutated ras gene promotes cell division without regulation by growth factors or other cell division stimulants