1. Unit 1: DNA and the Genome Structure and function of RNA

2. CFE Higher Biology DNA and the Genome RNA There is a second type of nucleic acid in the cell, called RNA. RNA plays a vital role in the production of protein from the code in the DNA.

3. CFE Higher Biology DNA and the Genome Differences between DNA and RNA Phosphate Ribose Sugar … and Uracil replaces thymine 5’ end 3’ end 5’ pronounced “5 prime” RNA nucleotides are similar in structure to DNA, except Ribose sugar replaces Deoxyribose sugar…

4. CFE Higher Biology DNA and the Genome

5. CFE Higher Biology DNA and the Genome DNARNA Double strandedSingle stranded Deoxyribose sugarRibose sugar Bases: A, T, C and GBases: A, U*, C and G *Uracil replaces thymine

6. CFE Higher Biology DNA and the Genome Types of RNA There are three types of RNA: 1.Messenger RNA (mRNA) 2.Transfer RNA (tRNA) 3.Ribosomal RNA (rRNA)

7. CFE Higher Biology DNA and the Genome mRNA mRNA is formed in the nucleus from free nucleotides and carries a copy of the DNA code from the nucleus to the ribosomes (where protein synthesis occurs). Organic Base Phosphate Ribose Sugar RNA nucleotide

8. CFE Higher Biology DNA and the Genome tRNA tRNA molecules collect amino acids and bring them to the ribosome to build proteins.

9. CFE Higher Biology DNA and the Genome rRNA rRNA molecules combine with proteins to create the ribosome – the organelle responsible for assembling proteins following the DNA code. Blue = Proteins Orange = rRNA subunit 1 Yellow = rRNA subunit 2 The Ribosome

10. Unit 1: DNA and the Genome Transcription

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

12. CFE Higher Biology DNA and the Genome Protein synthesis We will look at the process of protein synthesis in detail… Click here for an overview of protein synthesis

13. 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

14. 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.

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

16. 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.

17. 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.

18. CFE Higher Biology DNA and the Genome

19. 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.

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

21. 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.