Gene control

Gene Expression and Control

Gene expression refers to the process through which genetic information from a gene is utilised to produce a functional gene product like proteins or RNA.
The degree to which a gene is expressed, or turned on, can significantly influence the workings of cells and the development of an organism.
Gene regulation is the cellular control of the amount and timing of the appearance of the functional product of a gene.

A transcription factor is a protein that controls the rate of transcription from DNA to mRNA by binding to a specific DNA sequence.
They function as on/off switches for genes and are key players in the regulation of gene expression.
There are hundreds of transcription factors in a eukaryotic cell, each controlling a different set of genes.

In prokaryotes, gene expression is mostly controlled at the point of transcription initiation.
Operons are prevalent in prokaryotic gene regulation. An operon is a group of genes that are transcribed together, allowing for efficient regulation of gene expression.
Examples include the lac operon, which produces enzymes needed to digest lactose, and the trp operon, which produces enzymes necessary to synthesise tryptophan.

In eukaryotes, control of gene expression is more intricate than in prokaryotes.
It involves cellular mechanisms that modify the DNA (e.g., methylation), alter the proteins around which DNA is wound, and process the mRNA transcripts.
Gene expression can be controlled at multiple levels including the stages of transcription, post-transcription modification, RNA stability, and translation.

Epigenetics involves changes in gene expression that do not involve alterations to the genetic sequence.
Epigenetic modifications include DNA methylation and histone modification, which influence gene expression either by blocking access to the DNA or by altering the 3D arrangement of DNA within the nucleus.
Epigenetic changes can be stable and affect the traits of an organism, but unlike genetic mutations, they are reversible and do not affect the DNA sequence itself.

RNA interference (RNAi) is a natural mechanism within cells that uses small RNA molecules to control the activity of genes.
The process involves the use of small molecules of RNA to interfere with the expression of specific genes with complementary nucleotide sequences.
RNAi is widely used by researchers to silence genes in order to ascertain their function.