1. Alternative RNA Splicing
DNA and the Genome
Key Area 3d
Alternative RNA Splicing

2. Expressing different proteins from one gene
Learning Intentions
Expressing different proteins from one gene
Explain the mechanism by which different proteins can be expressed from one gene
Define ‘alternative RNA splicing’
Explain why many different mRNA molecules are produced from the same primary transcript

3. One Gene…Many Proteins
Alternative RNA Splicing

4. One gene…many proteins
Different proteins can be expressed from one gene as a result of:
Alternative RNA splicing

5. Genes to Proteins
The human genome is thought to contain between 20,000 – 25,000 genes but there are over 100,000 different proteins present in the human body How then is it possible to produce all of these proteins? The answer lies in the fact that some genes are able to produce more than one protein due to the process of alternative RNA splicing Different mRNA molecules are produced from the same primary transcript depending on which RNA segments are treated as exons and introns and which combination of exons are included in the mature RNA transcript

6. Alternative RNA Splicing
There are different methods of combining exons when they are spliced from the primary mRNA transcript:
Exon skipping – different exons are removed or included.
Mutually exclusive exons – one of two exons may be included but not both
Different mature mRNA transcripts are produced from the same primary mRNA transcript depending on which exons are retained

7. Exon Skipping
2 different mature mRNAs can be produced depending on which exons are included (or excluded).
The order of exons never changes!

8. Mutually Exclusive Exons
Only 1 of the 2 exons (shown in orange and green) can be included to make the mature mRNA

9. Alternative splicing animation

10. Two antibodies from one gene – an example
This diagram shows how 2 antibodies with different structures can be made from the one gene via alternative splicing
The antibody on the left has the exon for membrane binding present (and secreted exon cut out) and so it is found on the cell membrane of a white blood cell
The antibody on the right has had the secreted exon present (and the membrane bound exon spliced out) and so is found free in the bloodstream