Introducing DNA Jin Young Huh IB Biology

What is DNA?  Nucleic acid  Genetic information for  all living organisms  some viruses  DNA molecules: long-term storage of information  Made of simple subunits (nucleotides)

Nucleotides  Consists of three parts  Sugar  Phosphate group  Base  Adenine (A)  Cytosine (C)  Guanine (G)  Thymine (T)

Structure of DNA : Double Helix  Polymer of nucleic acids held together by nucleotides  Single turn of a helix= ten nucleotides

Building DNA Molecules  Two DNA nucleotides are linked together by a covalent bond between the sugar of one nucleotide and the phosphate group of the other

Building DNA Molecules  DNA molecules consist of two strands of nucleotides wound together into a double helix  Hydrogen bonds link the two strands together  Complementary base pairing  A-T  C-G

DNA Replication  Copy DNA  Produce new molecules  “Semi- conservative”  Each molecule consists of one new strand and one old strand from the parent DNA molecule

DNA Replication  Stage 1  Double helix unwound  Into strands by helicase  Stage 2  Free nucleotides form hydrogen bonds with the bases on the parent strands  Form a new strand  DNA polymerase  Stage 3  Daughter DNA molecules into double helix

Sources  MRC Laboratory of Molecular Biology, Cambridge, UK  lmb.cam.ac.uk/genome s/jong/dna.html lmb.cam.ac.uk/genome s/jong/dna.html  Science aid.co.uk 