DNA as the Genetic Material
  • The search for genetic material led to the discovery of DNA and through use of bacteria and phages we have evidence that DNA is genetic material.
  • When Griffith did his bacteria experiment, he discovered Transformation - a change in genotype and phenotype due to the assimilation of external DNA by a cell in bacteria.
  • Viruses that attack bacteria are know as Bacteriophages. they are also know as Phages
  • Hershey and Chase performed an experiment that proved that nucleic acid rather than proteins are the source of genetic materialFg10_06b.gif

Watson and Crick Discovered that DNA was a Double Helix
  • Watson and Crick discovered that DNA was in the shape of a double helix and that base pairs in the center "connect" them
  • DNA consists of two antiparallel sugar phosphate chains that wind around the interior where hydrogen bonds pair the nitogenous bases A to T and C to G

DNA Repair and Replication
  • During DNA replication, the DNA unwinds (DNA helicase) and each strand with its base pairs become an existing template for a new strand of DNA
  • Replication starts at the Origins of Replication. A "Y- shaped" region called the replication fork is the area where DNA enlongates
  • After that, DNA Polymerases, which are enzymes, attach themselves to the strand and then nucleotides align with corresponding bases.
  • It runs in a 5' -- 3' direction. When this occurs two types of strand are made: Leading Strand and Lagging Strands. The leading strand is the one that runs straight because the DNA Polymerase is continuously adding nucleotides. The lagging strand is put together by Okazaki Fragments that are later joined together by the enzyme DNA Ligase
  • After the pairing is done, DNA polymearse goes over to see if there were any incorrect pairing and if so changes the base pairs.
  • Other enzymes cut out damaged parts of DNA (nucleases)
Telomeres are at the end of DNA and they determine the age and life of the cell and they also become shorter with each replication.