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


Structure of dna point mutations



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


Structure of dna point mutations

DNA is always double stranded and in a helix.


Structure of dna point mutations

  • 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