Question

All cells in an embryo have the same heredity, yet they develop into different tissues and organs and organ systems. What is the process by which this happens?

Answer 1

The process of cells with the same genetic material and same common ancestor turning into different tissues is called 'differentiation.' No single cell expresses all of its genes at once. As cells differentiate, they down regulate or 'turn off' the genes involved in maintaining the undifferentiated state; they also up regulate or 'turn on' the genes involved in becoming specific kinds of cells, like bone cells or muscle cells. The processes by which the cell up and down regulates specific genes are short term (i.e. binding of transcription factors to regulatory elements in the DNA) and though long term activation or inactivation of the DNA by epigenetic modification of the proteins (called histones) that support the DNA. And covalent modification like methylation of the DNA itself.

The signals for which genes get turned on and off come from other differentiating cells - the organism senses that it already has bone tissues, so it does not make more bone cells.

Answer 2

thanx bluey....

Answer 3

yes but exist experiments. for example you can take the nucleus of the brain cell and transplate this to other different cell (hepatic, skin, etc), and the cell with the new nucleus never change to a cell brain it is mantained its form and funtion

Answer 4

If you're interested in this topic, then you would probably enjoy the recent book "The Epigenetics Revolution: How Modern Biology Is Rewriting Our Understanding of Genetics, Disease, and Inheritance by Nessa Carey". It's written for a lay audience, and was one of the better such books I've read. I learned lots of new stuff, and it was fascinating and entertaining the whole way.