| KW! | Active site/binding site has a specific 3o structure therefore is complementry |
| Gene Expression | - Every cell in your body has the same DNA, although there are lots of different cells with different functions
- Genes are turned on and off in cells this process is called GENE EXPRESSION.
- “every cell has the same orchestra, but they play different tunes” |
| Transcription Factors | - These are molecules that bind to the DNA PROMOTOR and are required to begin transcription
- Transcription factors will bind to a specific sequence of DNA, because the 3o structure is specific thus complementary to the seq. of DNA
- RNA polymerase will only bind once transcription factors have binded |
| Oestrogen | - Oestrogen is a steroid hormone
- It is lipid soluble so can diffuse through the cell membrane
- Oestrogen binds to a complementary shaped receptor on a transcription factor
- The change in tertiary structure removes the inhibitor
- The transcription factor diffuses into the nucleus and binds to DNA promotor region
- Transcription begins (because RNA polymerase binds) |
| Explain why oestrogen only leads to a gene expression in target cells? | - Transcription factors will only be complementary to target cells |
| siRNA | - Small Interfering RNA
- These are short pieces of double stranded RNA that can prevent gene expression by interfering with mRNA (breaking it down)
- They work by combining with an enzyme, then attach the enzyme to the complementary mRNA
- The enzyme then Digests mRNA |
| How does siRNA regulate gene expression ? (1) | - A mature mRNA leaves a nuclear pore
- This is converted into a double stranded RNA by an enzyme
- This is the broken into smaller sections, it is now siRNA |
| How does siRNA regulate gene expression ? (2) | - The siRNA joins to a RISC complex (enzyme)
- The original mRNA is removed
- This leaves a strand which is complementary to the original RNA strand |
| How does siRNA regulate gene expression ? (3) | - The RISC enzyme is guided to mRNA strand + hydrolyses it into shorter sections
- The mRNA can no longer be translated so the gene is silenced |
| What is the potential of siRNA | - Enables us to find the functioning of genes by switching them off
- Treating genetic disease by switching off faulty genes |
