Transcription/ Translation

1. Transcription/Translation Protein Synthesis

2. RNARIBONUCLEIC ACID • SINGLE STRANDED • RESPONSIBLE FOR BRINGING THE GENETIC INFO. FROM THE NUCLEUS TO THE CYTOSOL!

3. RNA Nucleotide • Phosphate group • Sugar molecule (ribose) • Nitrogenous bases • Adenine – URACIL • Cytosine - guanine

4. RNA • *

5. 3 Kinds of RNA • mRNA – (messenger) brings info from DNA in nucleus to cytosol in eukaryotic cells (uncoiled) • tRNA –(transfer) brings amino acids to mRNA for translation (hairpin shape) • rRNA –(ribosomal) most abundant, rRNA makes up the ribosomes where proteins are made (globular)

6. TRANSCRIPTION!!DNA  RNA • 1. INITIATION PHASE- RNA polymerase-initiates transcription by binding to region on DNA called PROMOTER (beginning of the gene) • only ONE of the DNA chains will be used for transcription it’s called the TEMPLATE (promoter dictates which of the two strands will be used) • 2. ELONGATION PHASE- RNA POLYMERASE attached to first DNA nucleotide of template chain – then begins adding complementary RNA nucleotides- • Read in a 3’ to 5’ direction

7. Cont. Transcription • 3. TERMINATION PHASE- transcription continues until RNA polymerase reaches a TERMINATION SIGNAL on the DNA- STOP CODON • 4. RNA polymerase releases both the DNA mol. And newly formed RNA mol.

8. Transcription

12. RNA replications

13. PROKARYOTES • Transcription and translation occur in the SAME place! • NO NUCLEUS!

14. Eukaryotes • 1. Before RNA leaves the nucleus: • 5’ G (guanine) cap is attached • 3’ polyA (adenine) tail is attached “many” • 2. These protect the RNA from attach by cellular enzymes and help ribosomes to recognize the mRNA • cap & tail are NOT translated

15. Cont. Eukaryotes • 3. INTRONS (non coding sequence) are removed • 4. EXONS (part of gene that are expressed) are joined to produce a mRNA molecule with a continuous coding sequence. • NOW RNA CAN LEAVE THE NUCLEUS!

17. Protein Synthesis • PROTEINS CARRY OUT THE GENETIC INSTRUCTIONS ENCODED IN AN ORGANISM’S DNA!!!!

18. TRANSLATIONThe process of assembling from info. Encoded in a mRNA! • 1. mRNA leaves nucleus • 2. mRNA migrates to ribosome in cytosol for protein synthesis • 3.amino acids floating in cytosol are transported to ribosomes by tRNA mole • 4. peptide bonds join the amino acids to make polypeptide chain

19. Vocabulary! • 1. GENETIC CODE: correlation between a nucleotide sequence and an amino acid sequence • 2. CODON: 3 mRNA nucleotides, codes for a specific amino acid (64) • 3. START CODON (AUG) & a.a. methionine • 4. STOP CODON (UAA, UAG, UGA) • 5. ANTICODON – 3 tRNA nucleotides carrying a specific amino acid!

20. 20 different kinds of amino acids • ….. But only 4 different kinds of nitrogen bases

21. Initiation Codon Marks the Start of an mRNA message • 3 PHASES: • 1. INITIATION • 2. ELONGATION • 3. TERMINATION

22. Ribosomefactory for polypeptides • Two subunits: • Large subunit (top) • Small subunit (bottom)

23. P site – holds tRNA carrying growing polypeptideA Site – holds tRNA carrying the next amino acid to be added

25. Forms a peptide bond

27. Protein Synthesis • *

28. Protein Synthesis • !

29. THE SUMMARY!- Central Dogma