Question

Briefly describe the five levels of regulation of eukaryotic gene expression

Answer 1

Gene regulation is the process of controlling which genes in a cells DNA are expressed ( used to make a functional product such as a protein)

In eukaryotes ,gene expression involves many steps and gene regulation can occur at any of these steps:-

Chromatin accessibility:- The structure of chromatin (DNA and it's organising proteins) can be regulated.

More open or relaxed chromatin makes a gene more available for transcription.

Transcription:- Transcription is a key regulatory point for many genes.

Sets of transcription factor proteins bind to specific DNA sequences in or near a gene and promote or repress it's transcription in to an RNA.

RNA Processing:- Splicing, capping andadditionof a poly- tail to an RNA molecule an be regulated, and so can exit from the nucleus.

Different mRNAs may be made from the same pre- mRNA by alternative splicing.

RNA Stability:- The life time of an mRNA molecule in the cytosol affects how many proteins can be made from it.

Small regulatory RNAs called miRNAs can bind to targetmRNAs and cause them to be chopped up.

Translation:- Translation of an mRNA may be increased or inhibited by regulators.

For instance, miRNAs sometimes block translation of their targetmRNAs ( rather than causing them to be chopped up)

protein activity:- Proteins can under go a variety of modification, such as being chopped up ortagged with chemical groups.

These modifications can be regulated and may affect the activity or behaviour of the proteins.

Although all stages of gene expression can be regulated , the main control point for many genes is transcription.

Later stages of regulation often refine the gene expression patterns that are roughedout during transcription.