Molecular Genetics: DNA

1
Molecular Genetics DNA

• Four roles for DNA
• Information storage
• Replication (reproduction)
• Day to day instructions to the cell
• Mutation

2
Molecular Genetics Mutation

• Mutations a permanent change in the genetic
  material of a cell or organism.
• Can be inherited.
• Can involve whole chromosomes or changes in DNA
  sequences.
• Chromosomal mutations-large scale
• Point mutations-single base
• Medium-size insertions or deletion mutations, too

3
Molecular Genetics Point mutation

• Point Mutations
• Change in a single nucleotide base pair.
• Example sickle cell anemia (illustration is for
  original mutation).

This is a base substitution A is substituted for
T in the gene-called mis-sense at the protein
level (Val for Glu) Nonsense mutation introduces
UAA, UGA or UAG codon
4
Molecular Genetics Point mutation

• Frame-shift mutation
• A change in the reading frame resulting from an
  insertion or deletion of nucleotides in the DNA
  sequence for a protein.
• Extremely harmful.

Normal JOE ATE THE HOT DOG After
deletion JEA TET HEH OTD OG
5
Molecular Genetics causes of mutation

• Mutagen-anything that causes a mutation
• Physical UV light, X-rays
• Chemical nitrosamines
• Biological jumping genes, some viruses,
• mistakes in copying DNA

6
Molecular Genetics reducing the number of
mutations

• DNA polymerase can correct most errors-
  proofreading
• Diploid genome means there is a backup copy
• Gene families may help
• Code is degenerate-many mutations are silent
• Large amount of non-coding DNA means that many
  mutations will occur in non-coding regions