DNA and Biotechnology

Transcription

1 DNA and Biotechnology

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3 What makes us human? Our DNA! It codes for our genes. (Gene = a piece of DNA that codes for a protein)

4 What is DNA and why is it so important? DNA is the blueprint for an organism. It contains genes (the instructions for assembling every protein in the body). Genes store and transmit heredity information used to build cells and do much of the work inside cells. It codes for all the similarities and differences between one organism and another. It can be used to determine familial and evolutionary relationships.

5 True or False: All humans have the same genes. True! Our genes make us human! True or False: All humans have the same alleles. False! Differences in our alleles are what makes us different. (Alleles different versions of a gene. Ex: brown and blond hair)

6 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 6

7 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 heatkilled S strain Study suggested that DNA was probably the genetic material copyright cmassengale 7

8 Griffith Experiment copyright cmassengale 8

9 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 32 P was injected into bacteria! copyright cmassengale 9

10 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 10

11 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 11

12 Rosalind Franklin copyright cmassengale 12

13 DNA Two strands coiled called a double helix Sides made of a pentose sugar Deoxyribose bonded to phosphate (PO 4 ) groups by phosphodiester bonds Center made of nitrogen bases bonded together by weak hydrogen bonds copyright cmassengale 13

14 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

15 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 15

16 Question: If there is 30% Adenine, how much Cytosine is present? copyright cmassengale 16

17 Answer: There would be 20% Cytosine Adenine (30%) = Thymine (30%) Guanine (20%) = Cytosine (20%) Therefore, 60% A-T and 40% C-G copyright cmassengale 17

18 What is a nucleotide? Strings of Nucleotides make up DNA Deoxyribose Sugar (part of backbone) Phosphate (part of backbone) Four Bases (on the inside) (A) Adenine (T) Thymine (G) Guanine (C) Cytosine

19 Cytosine Guanine Nitrogenous Base Adenine Nucleotide Pentose Sugar Thymine (DNA) Uracil (RNA) Ribose Inorganic Phosphate Deoxyribose

20 What makes nucleotides different? Purines: Adenine, Guanine Pyrimidines: Cytosine, Thymine

21 Who pairs with who? Adenine and Thymine Cytosine and Guanine A with T C with G Hydrogen bonds hold nucleotides together Humans have about 3 billion base pairs

22 What is the overall structure of DNA? (DeoxyriboNucleic Acid) Double Helix Spiral staircase Two strands of DNA Anti-parallel Hydrogen Bonds (weak) Connecting Strands

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24 What are the complimentary base pairs of the following sequence? A T G G C T A G T C G A T T A C T G A T G G C A A T A G C T

25 Quiz! 1. What is a double helix? 2. Write the complimentary DNA sequence of ACCTGATG 3. What are the three parts of a nucleotide? 4. How do nucleotides assemble to form DNA?

26 What is the central dogma? Sequence of nucleotides (ACTG) in DNA determines the sequence of amino acids of a protein The sequence of amino acids determines the shape of the protein. DNA Protein Appearance

27 What is the central dogma? source:

28 DNA Replication What does it mean to replicate something? Why does a cell need to replicate it s DNA? Cell division: Mitosis and Meiosis

29 Cell Cycle Mitosis: Process of cell division Interphase G1: Growth occurs S: DNA replication G2: More growth

30 DNA Replication What s happening? Physical modeling of DNA replication with S, P, and bases

31 Origin of replication Origin of replication Semiconservative Origin of replication Parental Origin of strand replication Daughter strand DNA Polymerase Replication Bubble Replication bubble Two daughter DNA molecules

32 What happens during replication? 1. Helicase unzips DNA forming a replication bubble 2. Complimentary DNA nucleotides are added by DNA Polymerase and other enzymes 3. Two new strands are formed Physical modeling of DNA replication with S, P, and bases Blue: Original strand of DNA Red: Complimentary base pairs are being added DNA Polymerase and other enzymes Simplistic: Good Animation:

33 Semi-Conservative Replication! One strand of old DNA acts as a template for the new strand of DNA Template = pre-existing pattern How does the DNA act as a template for replication? Complimentary base paring to make an exact copy of the sequence

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35 If every cell in my body has four feet of DNA, then how can the cell make a copy without the DNA getting all tangled? Replication bubbles Many places where the DNA opens for replication Example: Copying a book. Speed Race on the Board Here

36 Quiz 1. What is the purpose of DNA replication? (Why does DNA replication happen?) 2. What does semi-conservative replication mean? 3. Describe how DNA replication occurs. 4. Draw and label the parts of a nucleotide.

37 Review: Central Dogma DNA ATGGCGAAA TACCGCTTT Transcription RNA AUGGCGAAA UACCGCUUU Translation Protein met-ala-lys tyr---arg---phe The language of mrna is called Genetic code

38 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 38

39 DNA Replication 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 39

40 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 copyright cmassengale 40

41 copyright cmassengale 41

42 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 42

43 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 43

44 Question: What would be the complementary DNA strand for the following DNA sequence? DNA 5 -CGTATG-3 copyright cmassengale 44

45 Answer: DNA 5 -CGTATG-3 DNA 3 -GCATAC-5 copyright cmassengale 45