1. CFE Higher Biology DNA and the Genome Transcription

2. CFE Higher Biology DNA and the Genome Protein synthesis What is a gene? A gene is a section of DNA which carries the code for the production of one protein.

3. CFE Higher Biology DNA and the Genome DNA mRNA Protein Transcription Translation Ribosome Nucleus Overview of gene expression A G A G G T T G A C G A A T C T C C A A C T G C T T U C U C C A A C U G C U U codon ser pro thr ala

4. CFE Higher Biology DNA and the Genome Transcription Transcription is the synthesis of mRNA from a section of DNA. Transcription of a gene starts from a region of DNA known as the promoter.

5. CFE Higher Biology DNA and the Genome Promoter: Start of a gene Terminator: End of a gene

6. CFE Higher Biology DNA and the Genome RNA polymerase This enzyme is responsible for transcription. RNA polymerase binds at the promoter and unwinds the DNA.

7. CFE Higher Biology DNA and the Genome RNA polymerase adds nucleotides onto the 3’ end of the growing mRNA molecule. Due to the base-pairing rules the mRNA produced will be complementary to the DNA. The molecule elongates until it reaches the terminator sequence. The molecule produced is called the primary transcript.

8. CFE Higher Biology DNA and the Genome

9. CFE Higher Biology DNA and the Genome Modification of the primary transcript Not all the regions in a eukaryotic gene are required to produce the final protein. These non-coding regions are called introns. The coding regions are called exons.

10. CFE Higher Biology DNA and the Genome Primary transcript Mature transcript

11. CFE Higher Biology DNA and the Genome RNA splicing After the mRNA has been transcribed the introns are removed. The remaining exons are spliced together to form a continuous sequence. This is called the mature transcript. The mature transcript then leaves the nucleus to travel to the cytoplasm.