THE CENTRAL DOGMA Information Transfer

DNA Blueprint for protein synthesis Polymer of nucleotides Nucleotide = a 5 carbon sugar (deoxyribose), a phosphate group and a nitrogenous base (adenine, thymine, cytosine and guanine) A + G = purines = 2 rings; T and C = pyrimidines = 1 ring Base pairing rules = C + G and A + T

DNA Double Helix 2 nucleotide chains wrapped in a double spiral (twisted ladder) Structure discovered by Watson, Crick and Wilkins – Nobel Prize; Rosalind Franklin Alternating sugar - phosphate – sugar – phosphate ….. Covalently bonded – make up sides of ladder (AKA backbone) Bases covalently bonded to sugar; rungs of ladder are A, T, G and C hydrogen bonded

DNA Replication Process by which DNA is copied – S Phase of Interphase 2 nucleotide chains separate (helicase breaks H bonds) -> replication fork Topoisomerase = allows swiveling by nicking strand RNA Primase = sets down about 10 nucleotides first (complementary)

DNA Polymerase binds and adds complementary nucleotides to parent strand – can only add 5’ -> 3’ Discontinuous replication on lagging strand – Okazaki fragments – eventually linked together by ligase Other strand is leading strand; replication is continuous When replication is completed, 2 new exact copies of original DNA molecule are produced -> cell can now divide Replication = accurate; repair enzymes fix mutations (changes in nucleotide sequence)

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