Briefly describe the steps of DNA Replication.

1. Briefly describe the steps of DNA Replication. Agenda • Replication Math • Transcription: Making RNA

3. DNA Info • DNA never ever leaves the nucleus • DNA is the master copy of the directions a cell needs to live so it needs to be protected But DNA in the cytoplasm can be destroyed DNA in the nucleus is safe

4. RNA • RNA is a copy of DNA that goes out into the cytoplasm to tell the cell what to do in order to stay alive • RNA: ribonucleic acid • RNA is similar to DNA • Sugar is ribose not deoxyribose • Nitrogen Base thymine is replaced with Uracil • Single stranded

5. Deoxyribose Sugar Ribose Sugar Nitro-gen Base Nitro-gen Base Phos-phateGroup Phos-phateGroup RNA U – A G – C T – A G – C

6. 3 types of RNA • Messenger RNA (mRNA) – complementary to DNA • C=G, A=U • Travel from nucleus to ribosome • Direct synthesis of protein • Ribosomal RNA (rRNA) – associates with proteins to form ribosomes • Transfer RNA (tRNA) – transport amino acids to ribosome

8. Transcription • RNA is made from 1 gene in DNA • Specifically mRNA (messenger RNA) because it sends a message from DNA to the cytoplasm DNA safe in the nucleus To send a message to the cytoplasm Uses mRNA

9. Transcription • Unzip DNA • RNA Polymerase binds to synthesize RNA • Match up bases to one side of a gene in DNA in the 5’ to 3’ direction (adds to 3’ end) • Use Uracil instead of thymine • mRNA detaches from the DNA • mRNA moves out of the nucleus and into the cytoplasm

10. DNA mRNA mRNA Cytoplasm of cell Nucleus Transcription happens in the nucleus. An RNA copy of a gene is made. Then the mRNA that has been made moves out of the nucleus into the cytoplasm Once in the cytoplasm, the mRNA is used to make a protein

12. Transcribe your DNA(get your paper from replicating DNA) 1. Does the mRNA model more closely resemble the DNA strand from which it was transcribed or the complementary strand that wasn’t used?  Explain 2. Explain how the structure of DNA enables the molecule to be easily transcribed.  Whys is this important for genetic information? 3. Whys is RNA important to the cell?  How does an mRNA molecule carry information from DNA? 4. If DNA strand read AAC GTC GCG TAC, what would the mRNA strand be?

13. Briefly describe transcription. Agenda • Finish Transcribing DNA • Translation

14. A little more about RNA • RNA is shorter than DNA • DNA is interrupted by short sequences that are not in the final mRNA • These are called introns • Sequences that are kept in the final mRNA sequence are called exons

16. Translation

17. The Code • 20 amino acids (AA) used to make proteins • DNA provides at least 20 different codes • If each base coded for an AA then we could only get 4 AA • If a pair of bases coded for an AA then we could get 16 (4x4) • If 3 bases coded for an AA then we could get 64 (4x4x4)

18. The Code • We find that every 3 bases codes for an amino acid sequence • Some amino acids are repeated • Three base code is called a codon • All but 3 codons code for an amino acid • A chart was made to show each AA that DNA/mRNA codes for

20. Translation • mRNA is synthesized and moves to the ribosomes • Located on the Rough ER • mRNA then attaches to the ribosome • tRNA interprets the mRNA codon sequence and brings the appropriate amino acid • Several amino acids make proteins • Continues until a stop codon is reached (3)

21. tRNA • 3 base sequence at the bottom – anticodon • Matches the codon on the mRNA strand

22. Ribosome • 2 subunits – only together during translation • Attach the to mRNA strand • 3 grooves, E site, P site, and A site • Each groove holds a tRNA • E site – exit • P site – add amino acid to polypeptide chain • A site – new tRNA arrives

24. Translate your DNA Questions • Write your Amino Acid Sequence • Would you make a complete protein? Explain. • Transcribe the following DNA sequence into mRNA. Draw a line separating each codon: A T C G T C C A AA ….

25. Briefly describe translation Agenda for Thursday Nov 4th • Review Replication, transcription, and translation • Practice

26. Replication • DNA Helicase unzips DNA • Proteins bind to keep it apart • Primers bind to DNA strands • DNA Polymerase adds nucleotides to DNA • Leading – continuous adding of bases • Lagging – Okazaki fragments • DNA Ligase fills in gaps

27. Transcription • DNA Helicase unzips DNA • RNA Polymerase adds bases to the template strand of DNA • Only 1 strand of DNA gets copied • RNA detaches from DNA strand • RNA moves into cytoplasm

28. Translation • mRNA attaches to ribosomes • tRNA moves into ribosome • Anitcodon matches with mRNA strand and adds and amino acid • tRNA leaves ribosome • Stop codon is reached the amino acid chain (polypeptide) detaches from ribosome • Folds and creates a protein

29. DNA vs. RNA

32. How is RNA different from DNA Agenda for Friday Nov. 5th • Quiz • Practice with transcription and translation

33. Which RNA gets translated (mRNA, tRNA, rRNA)? Agenda for Monday Nov 8th • Replication, transcription, translation (one last time) • Questions 2 and 3 on page 335 • Questions 1 – 4 on page 341 • Practice • Gene Regulation