copyright cmassengale DNA and Replication copyright cmassengale 1 1
copyright cmassengale History of DNA copyright cmassengale 2 2
copyright cmassengale History of DNA Early scientists thought protein was the cell’s hereditary material because it was more complex than DNA Proteins were composed of 20 different amino acids in long polypeptide chains copyright cmassengale 3 3
copyright cmassengale Transformation Fred Griffith worked with virulent S and nonvirulent R strain Pneumoccocus bacteria He found that R strain could become virulent when it took in DNA from heat-killed S strain Study suggested that DNA was probably the genetic material copyright cmassengale 4
copyright cmassengale Griffith Experiment copyright cmassengale 5 5
copyright cmassengale History of DNA Chromosomes are made of both DNA and protein Experiments on bacteriophage viruses by Hershey & Chase proved that DNA was the cell’s genetic material Radioactive 32P was injected into bacteria! copyright cmassengale 6 6
Discovery of DNA Structure Erwin Chargaff showed the amounts of the four bases on DNA ( A,T,C,G) In a body or somatic cell: A = 30.3% T = 30.3% G = 19.5% C = 19.9% copyright cmassengale 7 7
copyright cmassengale Chargaff’s Rule Adenine must pair with Thymine Guanine must pair with Cytosine The bases form weak hydrogen bonds T A G C copyright cmassengale 8 8
copyright cmassengale DNA Structure Rosalind Franklin took diffraction x-ray photographs of DNA crystals In the 1950’s, Watson & Crick built the first model of DNA using Franklin’s x-rays copyright cmassengale 9 9
copyright cmassengale Rosalind Franklin copyright cmassengale 10 10
copyright cmassengale DNA Structure copyright cmassengale 11 11
copyright cmassengale DNA Two strands coiled called a double helix Sides made of a pentose sugar Deoxyribose bonded to phosphate (PO4) groups by phosphodiester bonds Center made of nitrogen bases bonded together by weak hydrogen bonds copyright cmassengale 12 12
copyright cmassengale DNA Double Helix Nitrogenous Base (A,T,G or C) “Rungs of ladder” “Legs of ladder” Phosphate & Sugar Backbone copyright cmassengale 13 13
copyright cmassengale Helix Most DNA has a right-hand twist with 10 base pairs in a complete turn Left twisted DNA is called Z-DNA or southpaw DNA Hot spots occur where right and left twisted DNA meet producing mutations copyright cmassengale 14 14
copyright cmassengale DNA Nucleotide O=P-O O Phosphate Group N Nitrogenous base (A, G, C, or T) O CH2 O C1 C4 C3 C2 5 Sugar (deoxyribose) copyright cmassengale 15 15
copyright cmassengale Pentose Sugar Carbons are numbered clockwise 1’ to 5’ CH2 O C1 C4 C3 C2 5 Sugar (deoxyribose) copyright cmassengale 16 16
copyright cmassengale DNA P O 1 2 3 4 5 P O 1 2 3 4 5 G C T A copyright cmassengale 17 17
copyright cmassengale Antiparallel Strands One strand of DNA goes from 5’ to 3’ (sugars) The other strand is opposite in direction going 3’ to 5’ (sugars) copyright cmassengale 18 18
copyright cmassengale Nitrogenous Bases Double ring PURINES Adenine (A) Guanine (G) Single ring PYRIMIDINES Thymine (T) Cytosine (C) A or G T or C copyright cmassengale 19 19
copyright cmassengale Base-Pairings Purines only pair with Pyrimidines Three hydrogen bonds required to bond Guanine & Cytosine C G 3 H-bonds copyright cmassengale 20 20
Two hydrogen bonds are required to bond Adenine & Thymine copyright cmassengale 21 21
copyright cmassengale Question: If there is 30% Adenine, how much Cytosine is present? copyright cmassengale 22 22
copyright cmassengale Answer: There would be 20% Cytosine Adenine (30%) = Thymine (30%) Guanine (20%) = Cytosine (20%) Therefore, 60% A-T and 40% C-G copyright cmassengale 23 23
Agenda 1.DNA Notes 2.Brainpop 3.Exit Ticket 4.Corrections/HW time
Reminder Community service this Saturday Show up at 8:30 by the main doors to be divided up into groups. Food was ordered for everyone.
Learning Target 5/5 SWBAT identify the steps to DNA replication, synthesis, and proof reading and describe the effects mutations can have on the message. VOCAB: Synthesis Mutation Template
copyright cmassengale Genetic Mutations copyright cmassengale 27 27
copyright cmassengale DNA Replication copyright cmassengale 28 28
copyright cmassengale NOTES: DNA Stands for Deoxyribonucleic acid Made up of subunits called nucleotides Nucleotide made of: 1. Phosphate group 2. 5-carbon sugar 3. Nitrogenous base copyright cmassengale 29 29
copyright cmassengale Replication Facts DNA has to be copied before a cell divides DNA is copied during the S or synthesis phase of interphase New cells will need identical DNA strands copyright cmassengale 30 30
Synthesis Phase (S phase) S phase during interphase of the cell cycle Nucleus of eukaryotes Mitosis -prophase -metaphase -anaphase -telophase G1 G2 S phase interphase DNA replication takes place in the S phase. copyright cmassengale 31 31
copyright cmassengale DNA Replication B Begins at Origins of Replication Two strands open forming Replication Forks (Y-shaped region) New strands grow at the forks B Replication Fork Parental DNA Molecule 3’ 5’ copyright cmassengale 32 32
copyright cmassengale DNA Replication B Enzyme Helicase unwinds and separates the 2 DNA strands by breaking the weak hydrogen bonds Single-Strand Binding Proteins attach and keep the 2 DNA strands separated and untwisted copyright cmassengale 33 33
copyright cmassengale DNA Replication Before new DNA strands can form, there must be RNA primers present to start the addition of new nucleotides Primase is the enzyme that synthesizes the RNA Primer DNA polymerase can then add the new nucleotides B copyright cmassengale 34 34
Direction of Replication DNA Replication B DNA polymerase can only add nucleotides to the 3’ end of the DNA This causes the NEW strand to be built in a 5’ to 3’ direction RNA Primer DNA Polymerase Nucleotide 5’ 3’ Direction of Replication copyright cmassengale 35 35
copyright cmassengale Proofreading New DNA DNA polymerase initially makes about 1 in 10,000 base pairing errors Enzymes proofread and correct these mistakes The new error rate for DNA that has been proofread is 1 in 1 billion base pairing errors copyright cmassengale 36 36
Tie in to last class What did we do? What was the purpose of the activity that we did?
Think About It Sometimes your teachers give you an example of how to do a project? What is the purpose of this? How can you relate this to DNA?
Vocabulary Building Mutation Template Replication DNA Base
Semiconservative Model of Replication Idea presented by Watson & Crick The two strands of the parental molecule separate, and each acts as a template for a new complementary strand New DNA consists of 1 PARENTAL (original) and 1 NEW strand of DNA DNA Template New DNA Parental DNA copyright cmassengale 40 40
copyright cmassengale DNA Damage & Repair Chemicals & ultraviolet radiation damage the DNA in our body cells Cells must continuously repair DAMAGED DNA Excision repair occurs when any of over 50 repair enzymes remove damaged parts of DNA DNA polymerase and DNA ligase replace and bond the new nucleotides together copyright cmassengale 41 41
Synthesis of the New DNA Strands The Leading Strand is synthesized as a single strand from the point of origin toward the opening replication fork RNA Primer DNA Polymerase Nucleotides 3’ 5’ copyright cmassengale 42 42
Exit Ticket Create a concept map OR using your own words, describe the relationship between DNA, genes, chromosomes, accurate information transmission, cells, organisms, and offspring.
Grade Pd 2 Pd 4 Pd 7 Pd 8 Pd 9 TEST RESULTS A 66-73 pts. 1 3 B 58-65 pts. 2 5 C 51-57 pts. 7 D 44-50 pts. F below 44 10 9 6 15 14
copyright cmassengale DNA Replication As the 2 DNA strands open at the origin, Replication Bubbles form Prokaryotes (bacteria) have a single bubble Eukaryotic chromosomes have MANY bubbles Bubbles copyright cmassengale 45 45
copyright cmassengale DNA Replication Enzyme Topoisomerase attaches to the 2 forks of the bubble to relieve stress on the DNA molecule as it separates Enzyme DNA Enzyme copyright cmassengale 46 46
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Remember HOW the Carbons Are Numbered! O=P-O Phosphate Group N Nitrogenous base (A, G, C, or T) CH2 O C1 C4 C3 C2 5 Sugar (deoxyribose) copyright cmassengale 48 48
Remember the Strands are Antiparallel O 1 2 3 4 5 P O 1 2 3 4 5 G C T A copyright cmassengale 49 49
Synthesis of the New DNA Strands The Lagging Strand is synthesized discontinuously against overall direction of replication This strand is made in MANY short segments It is replicated from the replication fork toward the origin RNA Primer Leading Strand DNA Polymerase 5’ 3’ Lagging Strand 5’ 3’ copyright cmassengale 50
Lagging Strand Segments Okazaki Fragments - series of short segments on the lagging strand Must be joined together by an enzyme Lagging Strand RNA Primer DNA Polymerase 3’ 5’ Okazaki Fragment copyright cmassengale 51 51
Joining of Okazaki Fragments The enzyme Ligase joins the Okazaki fragments together to make one strand Lagging Strand Okazaki Fragment 2 DNA ligase Okazaki Fragment 1 5’ 3’ copyright cmassengale 52 52
Replication of Strands Replication Fork Point of Origin copyright cmassengale 53 53
copyright cmassengale Exit Ticket Question: What would be the complementary DNA strand for the following DNA sequence? DNA 5’-CGTATG-3’ copyright cmassengale 54 54
copyright cmassengale Answer: DNA 5’-CGTATG-3’ DNA 3’-GCATAC-5’ copyright cmassengale 55 55