Notes

GENE EXPRESSION:
== The process of turning on a gene to produce RNA and protein is called gene expression
Prokaryotic Gene expression
==> Prokaryotic organisms are single-celled organisms that lack a cell nucleus, and their DNA therefore floats freely in the cell cytoplasm.
==> The processes of transcription and translation occur almost simultaneously.
==> In prokaryotic cells, the control of gene expression is mostly at the transcriptional level.
==> Proteins that are needed for a specific function, or that are involved in the same biochemical pathway, are encoded together in blocks called operons.
==> In prokaryotic cells, there are three types of regulatory molecules that can affect the expression of operons: repressors, activators, and inducers.
==> Repressors prevent transcription of a gene in response to an external stimulus, whereas activators increase the transcription of a gene in response to an external stimulus.
==>
Eukaryotic Gene expression
==> The process is complex
==> In eukaryotic cells, the DNA is contained inside the cell’s nucleus and there it is transcribed into RNA.
==> The synthesized RNA is then transported out of the nucleus into the cytoplasm, where ribosomes translate the RNA into protein.
==> The processes of transcription and translation are physically separated by the nuclear membrane; transcription occurs only within the nucleus, and translation occurs only
outside the nucleus in the cytoplasm.