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Dna
 

Dna

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    Dna Dna Presentation Transcript

    • WARM-UP #7
    • DNA (Deoxyribonucleic Acid)
    • Genetic material of cells…
      • GENES – units of genetic material that CODES FOR A SPECIFIC TRAIT
      • Called NUCLEIC ACIDS
      • DNA is made up of repeating molecules called NUCLEOTIDES
    • DNA Nucleotide O O=P-O O Phosphate Group N Nitrogenous base (A, G, C, or T) CH2 O C 1 C 4 C 3 C 2 5 Sugar (deoxyribose)
    • A HISTORY OF DNA
      • Discovery of the DNA double helix
      • A. Frederick Griffith – Discovers that a factor in diseased bacteria can transform harmless bacteria into deadly bacteria (1928)
      • B. Rosalind Franklin - X-ray photo of DNA.
      • (1952)
      • C. Watson and Crick - described the DNA molecule from Franklin’s X-ray.
      • (1953)
      SEE p. 292-293
    • Watson & Crick proposed…
      • DNA had specific pairing between the nitrogen bases:
      • ADENINE – THYMINE
      • CYTOSINE - GUANINE
      • DNA was made of 2 long stands of nucleotides arranged in a specific way called the “Complementary Rule”
    • DNA Double Helix Nitrogenous Base (A,T,G or C) “ Rungs of ladder” “ Legs of ladder” Phosphate & Sugar Backbone
    • DNA Double Helix P P P O O O 1 2 3 4 5 5 3 3 5 P P P O O O 1 2 3 4 5 5 3 5 3 G C T A
    • Nitrogenous Bases
      • PURINES
      • 1. Adenine (A)
      • 2. Guanine (G)
      • PYRIMIDINES
      • 3. Thymine (T)
      • 4. Cytosine (C)
      T or C A or G
    • Chargaff’s Rule
      • Adenine must pair with Thymine
      • Guanine must pair with Cytosine
      • Their amounts in a given DNA molecule will be about the same .
      G C T A
    • BASE-PAIRINGS C G H-bonds T A
    • Genetic Diversity…
      • Different arrangements of NUCLEOTIDES in a nucleic acid (DNA) provides the key to DIVERSITY among living organisms.
    • The Code of Life…
      • The “code” of the chromosome is the SPECIFIC ORDER that bases occur.
      • A T C G T A T G C G G…
    • DNA is wrapped tightly around histones and coiled tightly to form chromosomes See p. 297
    • DNA Replication
      • DNA must be copied
      • The DNA molecule produces 2 IDENTICAL new complementary strands following the rules of base pairing:
      • A-T, G-C
        • Each strand of the original DNA serves as a template for the new strand See p. 298
    • DNA Replication
      • Semiconservative Model:
      • 1. Watson and Crick showed: the two strands of the parental molecule separate, and each functions as a template for synthesis of a new complementary strand.
      • .
      Parental DNA DNA Template New DNA
        • 1. Why is replication necessary?
        • 2. When does replication occur?
        • 3. Describe how replication works.
        • Use the complementary rule to
        • create the complementary strand:
      A--- ? G--- ? C--- ? T--- ? A--- ? G--- ? A--- ? G--- ? C--- ? A--- ? G--- ? T--- ? Replication Quiz
        • 1. Why is replication necessary?
      • So both new cells will have the correct DNA
        • 2. When does replication occur?
        • During interphase (S phase).
        • 3. Describe how replication works.
        • Enzymes unzip DNA and complementary nucleotides join each original strand.
        • 4. Use the complementary rule to
        • create the complementary strand:
      A--- T G--- C C--- G T--- A A--- T G--- C A--- T G--- C C--- G A--- T G--- C T--- A Replication Quiz
    • (1961) Watson & Crick proposed…
      • … DNA controlled cell function by serving as a template for PROTEIN structure.
      • 3 Nucleotides = a triplet or CODON
      • (which code for a specific AMINO ACID)
      • See p.303
      • AMINO ACIDS are the building blocks of proteins.
    • DNA Transcription
      • DNA can “unzip” itself and RNA nucleotides match up to the DNA strand.
      • Both DNA & RNA are formed from NUCLEOTIDES and are called NUCLEIC acids.
      See p.301
    • DNA Translation
      • The cell uses information from “messenger” RNA to produce proteins
      See p.304-305 We will discuss details of this on a later date
    • Transcription/Translation Quiz
      • Why is transcription necessary?
      • Describe transcription.
      • Why is translation necessary?
      • Describe translation.
      • What are the main differences between DNA and RNA.
      • Using the chart on page 303, identify the amino acids coded for by these codons:
      • UGGCAGUGC
      • 1. Why is transcription necessary?
      • Transcription makes messenger RNA (MRNA) to carry the code for proteins out of the nucleus to the ribosomes in the cytoplasm.
      • 2. Describe transcription.
      • RNA polymerase binds to DNA, separates the strands, then uses one strand as a template to assemble MRNA.
      • 3. Why is translation necessary?
      • Translation assures that the right amino acids are joined together by peptides to form the correct protein.
      • 4. Describe translation.
      • The cell uses information from MRNA to produce proteins.
      • 5. What are the main differences between DNA and RNA.
      • DNA has deoxyribose, RNA has ribose; DNA has 2 strands, RNA has one strand; DNA has thymine, RNA has uracil.
      • Using the chart on page 303, identify the amino acids coded for by these codons: UGGCAGUGC
      • tryptophan-glutamine-cysteine
    • AMAZING DNA FACTS…
      • DNA from a single human cell extends in a single thread for almost 2 meters long!!!
      • It contains information equal to some 600,000 printed pages of 500 words each!!!
      • (a library of about 1,000 books)
    • LET’S REVIEW DNA… LM p.44
      • List the conclusions Griffith & Avery, Hershey & Chase drew from their experiments.
      • Summarize the relationship between genes & DNA.
      • Describe the overall structure of the DNA molecule.
      • What are the 4 kinds of bases?