Chapter 12 DNA & RNA

1. Chapter 12DNA & RNA Section 12-3RNA & Protein Synthesis

2. Objectives • What are the three main types of RNA? • What is transcription? • What is translation?

3. The Structure of RNA • Long Chains of Nucleotides • 5 Carbon Sugar ( Ribose ) • Phosphate Group • Nitrogenous Base • A, G, C, U ( no T ) • Single Stranded

4. Types of RNA RNA Mostly For Protein Synthesis Three Types of RNA Messenger RNA, mRNA Ribosomal RNA, rRNA Transfer RNA, tRNA

5. Types of RNA mRNA Template to construct protein from the DNA to the ribosome. rRNA Part of ribosome structure tRNA Transports amino acids from cytoplasm to the ribosomes

6. Transcription The process of copying part of the DNA nucleotide sequence into a complementary sequence of RNA Requires enzymes e.g. RNA Polymerase

7. RNA Polymerase

8. Transcription Key Concept: During transcription, RNA polymerase binds to DNA and separates the DNA strands. RNA Polymerase then uses one strand of DNA as a template to assemble nucleotides into RNA

9. Transcription Promoters • Regions on DNA that show where RNA Polymerase must bind to begin the Transcription of RNA • Specific base sequences act as signals • Other base sequences indicate stopping points

10. Transcription RNA Splicing • After the DNA is transcribed into RNA editing must be done to the nucleotide chain to make the RNA functional • Introns • Snipped out of the chain in the nucleus, non-functional segments

11. mRNA Splicing

12. RNA Splicing Exons Remaining, active segments of nucleotides

13. The Genetic Code Proteins are long chains of amino acids. There are 20 different amino acids The order of amino acids in the protein determine its shape and function

14. The Genetic Code There are 20 amino acids but only 4 bases in RNA Adenine A Cytosine C Guanine G Uracil U

15. The Genetic Code The genetic code consists of “words” three bases long Each “word” is called a Codon: three consecutive nucleotides that specifies a single amino acid

16. The Genetic Code For Example: UCGCACGGU = RNA Sequence UCG-CAC-GGU = Codons UCG codes for Serine CAC codes for Histidine GGU codes for Glycine

17. Code Wheel

18. The Genetic Code 4 Bases Codons Defined with 3 Bases There Are 64 Possible 3-base codons Since there are only 20 amino acids, some amino acids are represented by multiple codons See Figure 12-17

19. Translation Translation is the process of of decoding the mRNA into a polypeptide chain • Ribosomes • Read mRNA and construct the proteins

20. Translation Step A

21. Translation Step B

22. Translation Step C • Ribosome connects the amino acids together as they come into the ribosome • Ribosome disconnects the the 3rd amino acid from the ribosome to float into the cytoplasm

23. Translation • Step D • Polypeptide chain grows until the mRNA STOP Codon is reached • The ribosome then releases the polypeptide chain into the cytoplasm

24. The Roles of RNA & DNA DNA = Master Plan RNA = Blueprints of the Master Plan

25. Genes & Proteins • Genes are instruction for assembling proteins • Proteins are enzymes that catalyze and regulate chemical reactions • Pigments, antigens, regulators • Proteins are keys to function