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Nucleic Acids

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Nucleic Acids & Protein Synthesis Chapter 10.1 Structure of DNA Phosphate group Nitrogen-containing base ... – PowerPoint PPT presentation

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Title: Nucleic Acids


1
Nucleic Acids Protein Synthesis
  • Chapter 10.1

2
Structure of DNA
  • Phosphate group
    Nitrogen-containing base


  • Sugar (deoxyribose)

3
Three Parts of a DNA Nucleotide
  • Deoxyribose- sugar
  • Phosphate Group- a phosphorus atom surrounded by
    oxygen atoms
  • Nitrogen-containing base- contains a nitrogen atom

4
  • There are 4 nitrogen-containing bases found in
    DNA nucleotides
  • Adenine (A), guanine (G), cytosine (C), and
    thymine (T)

5
PURINES
  • Bases that have 2 rings of carbon nitrogen
    atoms
  • Includes adenine and guanine

6
PYRIMIDINES
  • bases that have 1 ring of carbon nitrogen atoms
  • Includes thymine and cytosine

7
DNA Spiral Staircase
  • Double helix- DNA is composed of 2 nucleotide
    chains wrapping around each other to form a
    double spiral
  • Discovered in 1953 by James Watson and Francis
    Crick

8
Evidence of the Double Helix
  • Rosalind Franklin and Maurice Wilkins had X-ray
    photographs of DNA crystals
  • 1962- Watson, Crick, Maurice received the Nobel
    Prize in Medicine for their work on DNA
  • Rosalind died in 1958 and was never acknowledged

9
Complementary Base Pairs
  • Cytosine pairs with Guanine
  • Adenine pairs with Thymine
  • Base-pairing rules- describe the pairing behavior
    of the bases (C-G and A-T)
  • Base pairs are connected by hydrogen bonds

10
  • C-G forms three Hydrogen bonds
  • A-T forms two Hydrogen bonds

11
Replication of DNA
  • Replication- the process of copying the DNA of a
    cell
  • Two nucleotide chains unwind and each chain acts
    as a template for a new chain
  • Replication fork- the point at which the 2 chains
    separate

12
  • Helicases- enzymes that separate the chains by
    breaking Hydrogen bonds
  • DNA polymerases- bind to the separated chains of
    DNA and help to assemble the new strands

13
Accuracy and Repair
  • Replication is very accurate (1 error in every
    10,000 paired nucleotides)
  • Mutation- a change in the nucleotide sequence at
    even 1 location
  • Mutations can have serious effects in new cells

14
  • Number of errors is reduced as enzymes proofread
    DNA and repair errors
  • DNA can be damaged by chemicals, pesticides, UV
    radiation from the sun, etc.
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