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DNA: PART II

DNA. DNA: PART II. LET”S REVIEW MITOSIS AND also COVER PROTEIN SYNTHESIS. Organization of the Chromatin. Threadlike chromatin = chromosomes = 46 DNA molecules and associated proteins Nondividing state = DNA molecules compacted coiled around core particle (histone protein)

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DNA: PART II

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  1. DNA DNA: PART II LET”S REVIEW MITOSIS AND also COVER PROTEIN SYNTHESIS

  2. Organization of the Chromatin • Threadlike chromatin = chromosomes = 46 DNA molecules and associated proteins • Nondividing state = DNA molecules compacted • coiled around core particle (histone protein) • zig-zagged, looped and coiled onto itself • Preparing to divide • DNA copies itself to form 2 parallel sister chromatids

  3. Discovery of the Double Helix • By 1900:components of DNA were known • sugar, phosphate and bases • By 1953: x ray diffraction determined geometry of DNA molecule • Nobel Prize awarded in 1962 to 3 men: Watson, Crick and Wilkins but not to Rosalind Franklin who died of cancer at 37 getting the x ray data that provided the answers.

  4. Figure 4.4

  5. Nucleotide Structure • DNA = polymer of nucleotides • Each nucleotide consist of • phosphate group • sugar • ribose (RNA) • deoxyribose (DNA) • nitrogenous base • in this picture = adenine

  6. Nitrogenous Bases • Purines - double ring • guanine • adenine • Pyrimidines - single ring • uracil - RNA only • thymine - DNA only • cytosine – both • DNA bases =CTAG • RNA bases = CUAG

  7. Complementary Base Pairing • Nitrogenous bases united by hydrogen bonds • DNA base pairings • A-T and C-G • Law of complementary base pairing • one strand determines base sequence of other Segment of DNA

  8. DNA Function • Code for protein synthesis • Gene - sequence of DNA nucleotides that codes for one protein • Genome - all the genes of one person • humans have estimated 30-35,000 genes • other 98% of DNA noncoding – “junk” or regulatory

  9. Chromosomes and Heredity • Heredity = transmission of genetic characteristics from parent to offspring • karyotype = chart of chromosomes at metaphase • 23 pairs homologous chromosomes in somatic cells (diploid number of chromosomes) • 1 chromosome inherited from each parent • 22 pairs called autosomes • one pair of sex chromosomes (X and Y) • normal female has 2 X chromosomes • normal male has one X and one Y chromosome • Sperm and egg (GAMETES) contain only 23 chromosomes • fertilized egg has diploid number of chromosomes

  10. 2 Basic Things Can Happen Which DNA • The ENTIRE DNA MOLECULE can Replicate: Then You have 2 from 1 (DNA REPLICATION---Leads to MITOSIS ..one cell goes to two cells. OR 2. Selected sections of the DNA strand(genes) can be expressed ( transcribed and into mRNA and Translated into proteins)

  11. Semi-conservative DNA replication: One strand “old, One strand, new”

  12. DNA Replication 1

  13. DNA Replication 2 • Law of complimentary base pairing allows building of one DNA strand based on the bases in 2nd strand • Steps of replication process • DNA helicase opens short segment of helix • replication fork is point of separation of 2 strands • DNA polymerase assembles new strand of DNA next to one of the old strands • 2 DNA polymerase enzymes at work simultaneously

  14. Errors and Mutations • Error rates of DNA polymerase • in bacteria, 3 errors per 100,000 bases copied • Proofreading and error correction • a small polymerase proofreads each new DNA strand and makes corrections • results in only 1 error per 1,000,000,000 bases copied • Mutations - changes in DNA structure due to replication errors or environmental factors • some cause no effect, some kill cell, turn it cancerous or cause genetic defects in future generations

  15. Mitosis • one cell divides into 2 daughter cells with identical copies of DNA • Functions of mitosis • embryonic development • tissue growth • replacement of dead cells • repair of injured tissues • Phases of mitosis (nuclear division) • prophase, metaphase, anaphase, telophase

  16. Embryo-Regions of Active Mitosis

  17. Meristems: Regions of Active Mitosis

  18. Timing of the Cell Cycle • G-1 This phase is longest ( ave-18-24 hours) remember this phase is the phase the most “normal” phase. ( Normal growth and metabolism activities- Synthesizing proteins needed for DNA synthesis) • S phase ( DNA replication (next longest) 8-10 hours • G-2 : relatively shorter : 4-6 hours ( Replicating centrioles and synthesizing enzymes that control cell division. • M phase is only 1-2 hours long.

  19. SO….Now that you know about Cloning Your Cells…. • What about The OTHER Reason for DNA…..EXPRESSING ONE OR MORE GENES……..for TO MAKE A PROTEIN PROTEIN SYNTHESIS Process will include: Transcription and Translation .

  20. Genetic Control of Cell Action through Protein Synthesis • DNA directs the synthesis of all cell proteins • including enzymes that direct the synthesis of nonproteins • Different cells synthesize different proteins • dependent upon differing gene activation • See Next Example

  21. Figure 4.5

  22. Transcription and Translation • The process of The majority of genes are expressed as the proteins they encode. The process occurs in two steps: Transcription = DNA → RNA • Translation = RNA → protein • Taken together, they make up the "central dogma" of biology: DNA → RNA → protein.

  23. What Do We Mean By 5’ 3’ Stuff? • Phosphate is • circle and 5 if • on top , 5’-3’ • Free 0H is 3 , • if on bottom visa • versa…3’-5’

  24. Posttranslational Modificationin Golgi Complex • Protein modified in cisterna, passed to next cisterna • Last golgi cisterna releases finished product as membrane bound vesicles • secretory vesicles • migrate to plasma membrane and release product by exocytosis • lysosomes • vesicles that remain in cell

  25. Polyribosomes and Signal Peptides • Polyribosome • cluster of 10-20 ribosomes reading mRNA at one time • horizontal filament - mRNA • large granules - ribosomes • beadlike chains projecting out - newly formed proteins • takes 20 seconds to assemble protein of 400 amino acids • cell may produce > 150,000 proteins/second • Signal peptide = beginning of chain of amino acids • determines protein’s destination within cell

  26. FROM GENE TO PROTEIN

  27. Polyribosomes translating a single looped mRNA.

  28. From Gene To Protein

  29. You Need RNA for PROTEIN SYNTHESIS • The process of protein synthesis involves: 1) Synthesis of mRNA from DNA template 2) Migration of mRNA from nucleus to cytoplasm ( the ribosome) where it will wait for another type of RNA ( tRNA) 3) tRNA will bring amino acids which are complimentary to the codons on mRNA

  30. Messenger RNA or M-RNA TRANSCRIPTION is the process to make…. • mRNA (messenger RNA) - encodes genetic information from DNA & carries it into the cytoplasm.t 5’ 3’ codon Each three consecutive mRNA bases forms a genetic code word (codon) that codes for a particular amino acid.

  31. Transfer or T- RNA • The unpaired regions form 3 loops. • Each kind of tRNA carries (at its 3′ end) one of the 20 amino acids • At one loop, 3 unpaired bases form an anticodon. • Base pairing between the anticodon and the complementary codon on a mRNA molecule brings the correct amino acid into the growing polypeptide.

  32. tRNA (transfer RNA) - transports specific amino acids to ribosome during protein synthesis (translation). Anticodon- specific sequence of 3 nucleotides; complementary to an mRNA codon. Amino acid accepting end Anticodon sequence determines the specific amino acid that binds to tRNA.

  33. RIBOSOMAL RNA or R-RNA • Ribosomal RNA (rRNA) • There are 4 kinds. In eukaryotes, these are 18S rRNA. One of these molecules, along with some 30 different protein molecules, is used to make the small subunitof the ribosome. • 28S, 5.8S, and 5S rRNA. One each of these molecules, along with some 45 different proteins, are used to make the large subunitof the ribosome

  34. rRNA (ribosomal RNA) - associates with proteins to form ribosomes. large subunit small subunit Subunits are separate in the cytoplasm, but join during protein synthesis (translation).

  35. Preview of Protein Synthesis • Transcription • messenger RNA (mRNA) is formed next to an activated gene • mRNA migrates to cytoplasm • Translation • mRNA code is “read” by ribosomal RNA as amino acids are assembled into a protein molecule • transfer RNA delivers the amino acids to the ribosome

  36. RNA: Structure and Function • RNA smaller than DNA (fewer bases) • transfer RNA (tRNA) 70 - 90 bases • messenger RNA (mRNA) over 10,000 bases • DNA has over a billion base pairs • Only one nucleotide chain (not a helix) • ribose replaces deoxyribose as the sugar • uracil replaces thymine as a nitrogenous base • Essential function • interpret DNA code • direct protein synthesis in the cytoplasm

  37. DNA: #2 GENE EXPRESSION =PROTEIN SYNTHESIS=TRANSLATION

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