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DNA

DNA. "The Blueprint of Life". DNA stands for... D eoxyribo N ucleic A cid. Important Scientists that determined DNA’s Importance. Frederick Griffith – bacterial transformation Oswald Avery – DNA = key to transformation Alfred Hershey & Martha Chase Bacteriophage transformation experiment

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DNA

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  1. DNA "The Blueprint of Life"

  2. DNA stands for...DeoxyriboNucleic Acid

  3. Important Scientists that determined DNA’s Importance • Frederick Griffith – bacterial transformation • Oswald Avery – DNA = key to transformation • Alfred Hershey & Martha Chase • Bacteriophage transformation experiment • Erwin Chargaff – base-pairing rules

  4. Discovering DNA: A Team Effort • Frederick Griffith (1928) • Question: How do bacteria make people sick? • Answer: Transformation

  5. Transformation • Process in which one strain of bacteria is changed by a gene(s) from another strain of bacteria

  6. Oswald Avery (1944) • Question: Which molecule is important for transformation? • Answer: DNA stores & transmits genetic info from 1 generation to the next

  7. Hershey & Chase (1952) • Question: Are genes made of DNA or protein? • Experiment: Which part of a bacteriophage enters the bacterium? • Answer: DNA

  8. Hershey/Chase Experiment

  9. Important Scientists in the “Race for the Double Helix” • Maurice Wilkins & Rosalind Franklin • X-ray diffraction • DNA must be a some type of spiral (helix) • DNA’s diameter is constant and stable

  10. DNA FACTS • established by James Watson and Francis Crick  • Shape of a double helix

  11. What is a Gene? • A length of DNA on a chromosome • May be in several parts • Exon – the expressed parts of the DNA sequence • Intron – the intervening, “junk DNA”, not expressed • Parts are cut, put together and then used to make RNA and proteins

  12. DNA: • codes for your genes  (traits) • made of repeating subunits called nucleotides

  13. What is a nucleotide? Has three parts:    PHOSPHATE DEOXYRIBOSE (sugar) BASE  (A,T,G,C)

  14. Base-Pair Rule Adenine <==> Thymine Guanine <==> Cytosine The sides of the DNA ladder are phosphate & sugar held together by  hydrogen bonds

  15. Base Pair Rule One side:     A   T   A      T   C   A      T   G   C      G   G   G Other side:

  16. How the Code Works The combination of A,T,G,C determines what traits you might have, for ex. C A T C A T   =  purple hair T A C T A C  =  yellow hair

  17. Think of the bases of DNA like letters.Letters form words....Words form sentences....              *endless               combinations

  18. Let's Review What We Know About DNA 1.  DNA stands for:   De _____ ribo ______  acid 2.  What is the shape of DNA? _______________ 3.  Who established the structure of DNA?  ____________ 4.  Adenine always pairs with _______________ 5.  The sides of the DNA ladder are deoxyribose and _____ 6.  Guanine always pairs with _____________ 7.  What is the complimentary sequence:   A A T  G  C A 8.  The two sides of DNA are held together by _______ bonds. 9.  DNA is composed of repeating subunits called ______________________ 10.  What are the 4 bases that make up the rungs of the DNA ladder? _______________________________________

  19. DNA Replication

  20. 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

  21. S phase DNA replication takes place in the S phase. G1 G2 interphase Mitosis -prophase -metaphase -anaphase -telophase Synthesis Phase (S phase) • S phase during interphase of the cell cycle • Nucleus of eukaryotes

  22. 3’ Parental DNA Molecule 5’ Replication Fork 3’ 5’ DNA Replication • Begins atOrigins of Replication • Two strands open forming Replication Forks (Y-shaped region) • New strands grow at the forks

  23. DNA Replication • Enzyme Helicase unwinds and separates the 2 DNA strands by breaking the weak hydrogen bonds • Single-Strand Binding Proteinsattach and keep the 2 DNA strands separated and untwisted

  24. 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

  25. DNA REPLICATION the process by which DNA makes a copy of itself (cell division) SEMI-CONSERVATIVE - half of the old strand is saved

  26. DNA Replication • Replication = Duplication • Happens in the S phase of Interphase • Must replicate before mitosis or meiosis I • Part of the double helix is unwound • Replication in small pieces (Okazaki fragments) • Enzyme stitches pieces together later

  27. RNA and Protein Synthesis RNA and Protein Synthesis

  28. Structure of RNA Genes – are coded DNA instructions that control production of proteins. 1. consists of a long chain of nucleotides (single strand)) 2. contains sugar ribose 3. contains nitrogenous base Uracil

  29. Types of RNA Messenger RNA  mRNA  carries copies of instructions Ribosomal RNA rRNA found in ribosomes where proteins are made. Transfer RNA tRNA brings in amino acids to make a protein.

  30. Transcription Process in which a sequence of DNA is copied into a complementary sequence of RNA RNA polymerase – enzyme used to open DNA strand and assemble a strand of RNA from DNA template. Promoters –regions of DNA that tells RNA polymerase where to start and stop.

  31. Genetic Code Proteins are made by joining AA. (20AA) Type of protein made is determined by sequence of AA. Code is read three letters at a time 3 Letters in called a codon codes for an AA.

  32. Genetic Code

  33. Translation • Ribosomes – read instructions from mRNA and makes proteins (Decoding of mRNA) • Translation begins when mRNA attaches to ribosome • mRNA moves through ribosome 1 codon at a time. • Codon is read and tRNA brings in the amino acid that is coded by that codon. *each tRNA carries only one kind of amino acid. *tRNA carries an anticodon that is complimentary to one mRNA codon. • Another tRNA comes in with the next amino acid and then the ribosomes bind the AA with a peptide bond. • The polypeptide chain grows until the ribosome reaches a stop codon. Then it releases the protein.

  34. Review

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