Regulation of gene expression

Gene expression ( pathway of modification )

All cells in your body contain the same DNA.

Not all cells produce the same proteins, as they all have different functions.

Protein production is regulated by genes, this means that certain genes need to be turned on or off.

Gene expression in prokaryotic cell

enzyme that catalyse metabolic reactions involved in basic cellular function are synthesised at a constant rate.

Enzymes that are only synthesised for specific conditions are made at a more variable rate.

what is an operon ?

A group of gene that function as a single transcription unit: first identified in prokaryotic cells.

what is an exon and intron ?

exon: the coding, expressing region of DNA

Intron: non coding region of DNA

The lac operon

E Coil metabolises glucose as respiratory substrate, however if glucose absent but lactose is present. the lactose induces the production of 2 enzymes.

what are of 2 enzymes that the lactose induces ?

Lactose permease

beta galactosidase

Lactose permease:

Allows lactose to enter the bacterial cell

beta galactosidase:

hydrolyses lactose to glucose and galactose

Gene expression in eukaryotic cell

Gene expression is much more complex in eukaryotic cells.

Transcription factors are proteins or short non-coding fragments of RNA that move along the DNA molecule and will bind to specific promotor regions, turning genes 'on' or 'off'.

Different cells will have different transcription factors present depending on the genes they need to express

Post transcriptional gene regulation

within a gene that are coding regions ( exons) and non coding regions ( intron)

All of the DNA is transcribed into mRNA. → primary mRNA

Endonuclease enzymes splice out the introns from the RNA, leaving the finalised mRNA. These introns may themselves code for proteins, or can act as transcription factors, or do nothing!