Information molecules Nucleic acids: Information molecules 2006-2007

Nucleic Acids Examples DNA DeoxyriboNucleic Acid RNA RiboNucleic Acid

Nucleic Acids Function: genetic material stores information genes blueprint for building proteins DNA  RNA  proteins DNA proteins

Nucleic acids 5 different nucleotides Building block = nucleotides nucleotide – nucleotide – nucleotide – nucleotide 5 different nucleotides different nitrogen bases A, T, C, G, U Nitrogen bases I’m the A,T,C,G or U part! phosphate sugar N base

Nucleotide chains Nucleic acids nucleotides chained into a polymer DNA phosphate sugar N base Nucleic acids nucleotides chained into a polymer DNA double-sided double helix A, C, G, T RNA single-sided A, C, G, U phosphate sugar N base strong bonds phosphate sugar N base phosphate sugar N base RNA

Deoxyribonucleic Acid DNA Structure & Replication

Nitrogen Bases in DNA Four different types of bases 1. Adenine (A) 2. Guanine (G) 3. Cytosine (C) 4. Thymine (T) Base paring rules: Adenine binds to Thymine (A-T) Cytosine binds to Guanine (C-G)

Example ACTGCCGAAT TGACGGCTTA

Copying DNA Replication copy DNA 2 strands of DNA helix are complementary have one, can build other when cells divide, they must duplicate DNA exactly for the new “daughter” cells Why is this a good system?

Newly copied strands of DNA DNA replication Copying DNA pairing of the bases allows each strand to serve as a pattern for a new strand The greatest understatement in biology! Newly copied strands of DNA

Two (of the many) enzymes needed for DNA replication Helicase – breaks the hydrogen bonds between bases to unwind the DNA DNA polymerases – bring new nucleotides into place, proofreads new strands as they form

First Glimpse of DNA Franklin, trained as a chemist, was expert in deducing the structure of molecules by firing X-rays through them. Her images of DNA - disclosed without her knowledge - put Watson and Crick on the track towards the right structure. She went on to do pioneering work on the structures of viruses. . Rosalind Franklin (1920-58)

Rosalind Franklin and her X-ray diffraction photo of DNA First Glimpse of DNA Rosalind Franklin and her X-ray diffraction photo of DNA

The Double Helix Watson and Crick (1953) discovered the structure of DNA to be a double helix or “spiral staircase” of two strands of nucleotides twisting around a central axis. Names for DNA…double helix, twisted staircase

Watson and Crick … and others… 1953 | 1962