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.