Dna , Protein Synthesis, and gene expression

1. Dna, Protein Synthesis, and gene expression

2. Inheritance

3. Search for the Genetic Code • Griffith’s Transformation Experiment (1928)

4. Avery, MacLeod, and McCarty (1944) • Repeated Griffith’s experiments • Used enzymes to destroy one of the _____________ during each round • Transformation was only stopped when ______ was destroyed

5. Hersey and Chase (1952)

6. Levene • Discovered the sugar difference between RNA and DNA • RNA- ____________ • DNA- ____________ • Discovered the components of a nucleotide • 5-carbon __________ • Phosphate group • Nitrogenous ________ (four types)

7. Chargaff • DNA contains equal amounts adenine (A) and thymine (T) and equal amounts cytosine (C) and guanine (G) • The amounts of A and T does _____ have to equal the amounts of C and G • Known as Chargaff’s rule

8. Franklin • Created X-ray diffraction images of DNA • Photo 51 allowed scientists to create a model of the sugar phosphate backbone (helix) • Close to figuring out bases • Picture shown to Watson and Crick without her knowing by colleague Wilkins

9. Watson and Crick • Able to make backbone based on Photo 51 • First to propose structure of DNA • Watson, Crick, and Wilkins received Nobel Prize

10. DNA Nucleotides • Three Parts • Phosphate Group (PO4) • Deoxyribose • Nitrogenous Base • Adenine (A) • Guanine (G) • Thymine (T) • Cytosine (C)

11. DNA Bases • Pyrimidines- _________ structure; C and T • Purines- __________ structure; A and G

12. DNA Backbone • Composed of phospate groups and sugar • Strands of DNA are ______________ • One runs 3’ to 5’; other runs 5’ to 3’

13. Complementary Base Pairing • A always pairs with T • Held together by ___ hydrogen bonds • C always pairs with G • Held together by ____ hydrogen bonds

14. Double Helix

15. DNA Coiling • Double Helix • ________________ • Helix is wrapped around bundle of eight histone proteins (a pair of each of the four types) • Fifth type of histone anchors the nucleosome to linker regions of DNA • 30 nm fiber- coiling of nucleosomes • _________ proteins- 30 nm fibers coil around the protein

16. Forms of DNA • __________- found throughout most of cell cycle • Chromosome- tightly packed DNA form during _________________

17. <> DNA Replication • Copy DNA into ______ • Performed during ____ phase of Interphase • Occurs before division in mitosis and meiosis • ___________________ • Each original DNA is still intact • Each original strand has a new partner (a newly made complement)

18. DNA Replication (cont) • Step 1- Unwinding of DNA stand • Performed by ____________ • Held apart by binding proteins • Occurs at many replication fork along the length of the strand • Step 2- Formation of RNA primers • Performed by __________ • Complementary base pairs are lined up to form the short primer

19. DNA Replication (cont) • Step 3- Replication • Performed by ___________________(DNAP) • DNAP can only attach bases to existing polymer (primer) • DNAP bring in complementary base pairs for each stand of DNA • Can only replicate in the ________ direction • 3’ to 5’ original strand is replicated continously • 5’ to 3’ is replicated discontinously in sections called Okazaki fragments

20. DNA Replication (cont) • Step 4- Sealing the Backbone • Performed by ____________ • Bonds backbones of fragments together • Step 5- Proofreading • Performed by ___________ • Checks bases and cuts out incorrect one to replace them with the correct one • Cuts out RNA primer and replaces with DNA nucleotides • Ligase seals all the backbones

22. From Gene to Protein • Genes code for protein; protein creates _________ • Protein Synthesis- creating a protein • Transcription- _______________ • Occurs in the ____________ • DNA is copied into messenger RNA (mRNA) • mRNA takes message to ___________ • Translation- ______________ • Occurs in cytoplasm at ____________ • mRNA is decoded into amino acids • Transfer RNA (tRNA) brings amino acids to ribosome

23. RNA Nucleotides • Three parts • Phosphate Group (PO4) • Ribose • Nitrogenous Base • Adenine (A) • Guanine (G) • Uracil (U) • Cytosine (C)

24. Ribosome Structure • Single Strand of Nucleotides • Shape will be determined by base pairing within the strand

25. Types of RNA • Three Major Types • mRNA- • Copy of DNA instructions • Also called ______________ • 500-4500 bases; depending on size of gene • Every three bases are called a ___________ • tRNA- • 75-80 bases that bind in cloverleaf shape • One end bonds to a specific amino acid • One end has a three base code called the _________ • Ribosomal RNA (rRNA)- • 100-3000 bases long • Form structure of ribosome with proteins • ___________- catalyze peptide bond formation between amino acids

26. Transcription • Step 1- Initiation • _________ binding protein (transcription factor) binds to TATA box within gene promoter region • Other transcription factors bind to this area forming complex • RNA polymerase binds to complex • Step 2- Elongation • RNA polymerase adds RNA nucleotides complementary to DNA • Only occurs in _______direction (reading the 3’ to 5’ DNA strand) • DNA stand being copied is called the ________; the other DNA strand not being copied is the _________ strand • The coding strand may be the template strand for another gene

27. Transcription (cont) • Step 3- Termination • RNA polymerase reaches a terminator sequence in DNA • Transcription is stopped • More than one transcript may be forming at a site at one time

29. Base Pairing Rules • If DNA is A • Then RNA is ___ • If DNA is T • Then RNA is ___ • If DNA is C • Then RNA is ____ • If DNA is G • Then RNA is ___

30. Processing mRNA • Transcript is altered in the nucleus before it leaves • Cap is placed at 5’ end • G base is inverted and _____________ • Poly A tail • Tail of around 200 adenines added to __________ • Removal of Introns • Pre-mRNA still contains sections that don’t code for protein and must be spliced out of transcript • Some introns are ribozymes that associate with proteins to form small nuclear ribonucleoproteins (snRNP’s) that will preform the splicing • Final transcript only contains ___________

31. Processing mRNA (cont)

32. Consequences of Processing • We create more proteins than we have genes • How do we do it? • Alternate splicing- mRNA is spliced to be shorter or longer to create a different protein • Different use of introns and exons- same pre-mRNA may have different areas spliced depending on the protein to be made

33. Translation • Step 1- Initiation • mRNA leader sequence bond to small ribosome subunit • First codon (always AUG) bonds with tRNAanticodon (UAC); this type of tRNA always has methionine attached • Step 2- Elongation • Large subunit attaches to small subunit • First codon/anticodon are put in the P site • A site exposes the second codon • The matching tRNAanticodon base pairs with the exposed codon bringing its amino acid • A peptide bond forms between the amino acids (catalyzed by a ribozyme) • The mRNA shifts down a spot • P site holds second codon with two amino acids attached • A site exposes next codon to base pairs with a matching anticodon • First tRNa (UAC) returns to cytoplasm to find another methionine

34. Translation (cont) • Step 3- Termination • Exposed codon at A site is one of the stop codons • No tRNA’s match; release factor binds and releases mRNA and poypeptide • mRNA may be translated by several ribosomes at the same time

36. Cystic Fibrosis

37. Protein Folding • Creates final ______________ of protein • Occurs in ER • Shape is created by • Attraction between neighboring amino acids • Polarity of amino acids • Sulfur bridges

38. Protein Folding (cont) • Chaperone proteins stabilize shapes as the form • Folding catalysts held fold protein • Folding sensors proofread shape • Misfolded proteins are tagged • Can be refolded properly • Could be destroyed by proteasome • 1⁰- ________________________________ • 2⁰- localized folding (α- helix and β-sheet) • 3 ⁰- _________ polypeptide folds together • 4 ⁰- ________________ polypeptide folds together

39. Protein Folding (cont)

40. Gene Expression • Not all genes are expressed at the same time • An organisms expresses genes at different times in different areas • Each cell type will express a different subset of genes • This can be seen by looking at the ____________

41. What Effects Gene Expression? • Chromatin Remodeling • Histones can expose or shield gene; groups can be added to histone to change it • Acetyl and phosphate groups- turn on gene when added • ___________ groups- turn off gene when added • RNA interference (RNAi) • RNA form a double strand when a single strand makes a hairpin turn and bonds with itself • Dicer (enzyme) cuts the RNA into small segments called small interfering RNA’s (siRNA’s) • siRNA’s • Methylatehistones • Attach to transcrpts, tagging them to be destroyed

42. Noncoding Regions of DNA • Do not code for protein • RNA’s besides mRNA • Introns • Promotors and control regions • Repeats • Transposons- repeats that can move and insert into new chromosomes • Telemeres • Centromeres