1. (3) Gene Expression Gene Expression (A) What is Gene Expression?
(E) Splicing and post-translational modification
(B) Structure and Functions of RNA
(D) Translation
(C) Transcription

2. Gene Expression (E)
Name the 2 process which can lead to different proteins being expressed from one gene
Describe what is meant by alternative RNA splicing
Describe 3 ways in which a protein can be modified
State what alternative RNA splicing and post translational modification of one gene can lead to

3. Varying Protein Expression
Different proteins can be expressed from one gene.
There are 2 processes which allow for this:
Alternative RNA splicing
Different mRNA molecules are produced from the same primary transcript depending on which RNA segments are treated as exons and introns.
Post-translational modification
The post-translation protein structure can be modified by cutting and combining it with polypeptide chains or by adding phosphate or carbohydrate groups to the protein

4. Alternative Splicing of the SAME gene

5. Alternative Splicing of the SAME gene
One gene can produce many different mature mRNA and therefore proteins by a process known as alternative RNA splicing
TASK: Using the following primary transcript show how many different mature mRNA molecules can be produced:

6. Post Translational Modification
Once translation is complete, further modifications may be required to enable a protein to perform its specific function.
Cleavage:
The process of cutting a single polypeptide (by enzymes) into smaller, active sections held together by sulphur bridges

7. Molecular Addition:
Proteins can have additions of carbohydrates or phosphates groups
Example – mucus is a glycoprotein (protein with carbohydrate).
Example – some enzymes require a phosphate group to make them functional (phosphorylation)

8. Where does all this happen?
animation: Golgi Body

9. Sectretion of proteins – ER, Golgi and vesicles
1. Vesicle containing freshly synthesised protein pinches off
2. Pinched vesicles join up to form Golgi apparatus
3. Protein processed in the Golgi usually sugar is added
R.E.R.
4. Vesicles with finished protein pinched off
5. Vesicles move towards the cell membrane
Cell membrane
Secretory Cell
6. Vesicle fuses with cell membrane
7. Protein secreted

10. Gene Expression (E)
Name the 2 process which can lead to different proteins being expressed from one gene
Describe what is meant by alternative RNA splicing
Describe 3 ways in which a protein can be modified
State what alternative RNA splicing and post translational modification of one gene can lead to