Small Interferring RNA. (SiRNA)

Quick recap of oestrogen first - transcription stimulated by transcription factor, which has to bind to a specific region on the DNA. Can be inhibited. Oestrogen dissolves through phospholipid bilayer, as it is lipid soluble. Combines with receptor of transcription factor (complimentary). Changes the shape of DNA binding site, releasing inhibitor. Transcription factor can now join with DNA and stimulate transcription.

SO. The transcription factors can be inhibited. Oestrogen bind to the transcription factor on the receptor. Changes molecule shape, including DNA binding site. Releases inhibitor, and can now bind to DNA.

Righto. :P

So, now on to how SiRNA effects gene expression.

Small interferring RNA are little sections of RNA, double stranded. It prevents gene expression my breaking down mRNA.

1. Enzyme breaks down double stranded chains of mRNA into smaller sections, called SiRNA.
2. One strand of the SiRNA combines with an enzyme.
3. This one strand then pairs with the complimentary section of bases on a single stranded chain of mRNA.
4. The enzyme then cuts the mRNA down into smaller sections.

The effect this has? With a broken chain of the mRNA, there is not the correct sequence of triplet codons, meaning incorrect amino acids are produced/not all of the amino acids necessary are produced - meaning the protein outcome will not have the same teritary structure, and therefore, shape, and possibly will not function in the same way. The gene is not expressed.

How this can be used? Use of SiRNA to block the genes that cause some diseases, or to identifiy the role of particular genes by eliminating them, and study the effects/missing chracteristics.