DNA, Chromosomes, and DNA Replication

1. DNA, Chromosomes, and DNA Replication Chapter 12

2. Who are the key contributors? • Frederick Griffith • Oswald Avery • Alfred Henry and Martha Chase • Chargaff • Rosalind Franklin • Francis Crick and James Watson

3. Griffith

4. Frederick Griffith • Responsible for transformation • Process in which one strain of bacteria is changed by gene(s) from another strain • Worked with mice and pnuemonia

5. Avery

6. Oswald Avery • Responsible for determining that the molecule important in transformation was nucleic acid DNA • Took heat-killed bacteria and made extract • Enzymes for lipids, proteins, and carbohydrates—no effect • Still smooth strain • Enzymes for nucleic acid—rough strain • Smooth strain not transformed

7. Hershey & Chase

8. Alfred Hershey and Martha Chase • Determined that the genetic material is made out of DNA, not protein • Used radioactive labels • Sulfur-35 for protein • Phosphorus-32 for nucleic acid

10. Chargaff • Looked at numerous organisms • Compared concentrations of nitrogenous bases (bases) • What do you notice? _________________________ Chargaff had no idea WHY this was happening!

11. Rosalind Franklin • Used X-ray diffraction to study image of DNA • Helical shape • Twisted strands • 2 strands • Bases near middle

13. Francis Crick and James Watson • Built 3-D models of DNA • Used work of everyone before them • Model: double helix • Twisted ladder • H-bonds between nitrogenous bases • Base pairing: A with T, G with C • EXPLAINS CHARGAFF

14. DNA structure • Made up of nucleotides • 5 C sugar • Deoxyribose • Phosphate group • Nitrogenous base

15. DNA isolation virtual lab DNA condensation • Very condensed • 1 cell holds 1m DNA • How?

16. DNA condensation

17. DNA condensation • DNA coils around proteins called histones • These coil into structures called nucleosomes • This coils further into supercoils • And then eventually chromosomes • Seen only during cell division (mitosis)

18. DNA replication • DNA is AWESOME • Each strand has all the information it needs to make its partner (complimentary strand) • Strand 1: ATT GAC TAC GGA TTC • Strand 2: TAA CTG ATG CCT AAG

19. DNA Replication • Prokaryotes start replicating in one place and go to completion • Eukaryotes start replicating in hundreds of places and meet up • Opening called a “replication fork”

20. Steps of Replication • Enzyme unzips DNA (helicase) • Breaks H bonds • Lots of enzymes • Now two separate strands • DNA polymerase (enzyme) makes a new strand of DNA from the old strand • From base-pairing rules

21. Replication A G C C T A AG C T T C G G A T T C G A T C G G A T T C G A A G C C T A AG C T DNA Replication Video

23. RNA & Protein Synthesis 12-3

24. RNA Structure • RNA has 3 main differences from DNA • Ribose instead of deoxyribose • Uracil instead of thymine • Single stranded instead of double stranded

25. Messenger mRNA Serve as messengers from DNA to rest of cell Types of RNA • Ribosomal • rRNA • Site of protein synthesis • Transfer • tRNA • Transfers amino acid to ribosome

26. Transcription • DNARNA • RNA polymerase binds to DNA • Special site called promoter • RNA polymerase makes complimentary strand out of RNA nucleotides Transcription Video

28. Transcription • Practice • DNA: TAA GTC AGT CAC TTC • RNA: • DNA: GGC TTA GGT CCT ATG • RNA:

29. The Genetic Code • How to you get from RNA to protein? • Proteins are made from amino acids • “Language” of mRNA is called the genetic code • Each amino acid has a “code” of three mRNA nucleotides • Called a codon

30. The Genetic Code

31. The Genetic Code • 20 amino acids • 64 possible codons • Some amino acids have more than one codon • “Start” codon—initiates translation • AUG • “Stop” codon—terminates translation • UAA, UAG, UGA

32. The Genetic Code • Let’s look at one half of DNA • DNA: AGCGTGCCA • RNA: UCGCACGGU • Into three-letter codons UCG-CAC-GGU • Amino acids: Serine-Histidine-Glycine

33. Translation • Translation is the process of taking the mRNA information and turning it into a polypeptide chain

35. Translation Steps • mRNA is transcribed in the nucleus • Exits via nuclear pore to cytoplasm • Attaches to a ribosome • Translation begins at “AUG” (start codon) • tRNAmolecule that has methionine (amino acid) and anticodon UAC attaches • Ribosome binds next codon/anticodon pair

37. Translation Steps • Ribosome joins 2 amino acids—peptide bond • tRNA for methionine breaks off • Ribosome binds next codon/anticodon pair • Joins these amino acids • Lather, rinse, repeat

38. Translation Steps • The process stops when… • The ribsosome reaches either • UAA • UAG • UGA More Protein Synthesis Protein Synthesis Video

39. Mutations Section 12-4

40. Kinds of Mutations • Point Mutations • Changes in one or a few nucleotides • Types of point mutations • Substitutions • Insertions • Deletions

41. Substitution One base is changed to another CT Usually affects only one (if any) amino acids Kinds of Mutations

42. Kinds of Mutations • Practice substitution • RNA strand: UAC-CCG-UAG-UUC-UAA • Original a.a: • RNA sub: UAC-CCA-UAG-UUC-UAA • Change? • RNA sub: UAC-CCG-UAG-UUC-UAC • Change?

43. Kinds of Mutations • Insertions & Deletions • One nucleotide is added or deleted • Called a frameshift mutation • Effects everything “downstream” • Can drastically change/destroy a protein’s function

45. Kinds of Mutations • Practice insertion & deletion • RNA strand: UAG-CCG-UAG-UUC-UAA • Original a.a: • RNA ins: UAG-CCGGUAGUUCUAA • Change? • RNA del: UAG-CCGUAGUUCUAC • Change?

46. Kinds of Mutations • Chromosomal mutations • Changes in the number or structure of chromosomes • Types: • Deletion • Duplication • Inversion • Translocation

47. Deletion: loss of all or part of chromosome Duplication: extra copies of chromosome parts Inversion: reverses the direction of parts of chromosomes Translocation: one part breaks off and attaches to another chromosome NOT CROSSING OVER!!!