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Structure of DNA & Point Mutations

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Structure of DNA & Point Mutations. Text ref 6.1 and 6.2. The Chemical Composition of DNA. Three main components: Pentose sugar (5 carbon ring) Phosphate group with negative charge Nitrogenous base. Three components together = nucleotide

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the chemical composition of dna
The Chemical Composition of DNA
  • Three main components:
  • Pentose sugar (5 carbon ring)
  • Phosphate group with negative charge
  • Nitrogenous base
slide3

Three components together = nucleotide

  • DNA is made of MANY nucleotides in repeating units!
dna structure
DNA structure:
  • Amount of A = T
  • Amount of G = C
  • DNA has a phosphate-sugar “backbone”, and bases that “pair up” in the middle of the molecule.
  • A always pairs with T
  • G always pairs with C
slide7

Strands of DNA are always complementary

  • This means they “match up”
  • Ribosomes read DNA in groups of three nucleotides = instructions to build proteins!
point mutations
Point Mutations
  • Replicating cells do not copy genetic info in DNA accurately.
  • Three major types of point mutations:
  • Base-pair substitutions
  • Insertions
  • Deletions
base pair substitutions
Base-Pair Substitutions:
  • One nitrogenous base is accidently replaced with another base.
insertions
Insertions:
  • One or more nitrogenous base(s) is inserted during the copying process.
deletions
Deletions:
  • One or more nitrogenous base(s) is deleted during the copying process.
homework
Homework
  • Page 233 #2, 4
  • Page 239 #2, 3
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