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NUCLEOTIDE MONOMER

NUCLEOTIDE MONOMER. H. 5. Pyrimidines (single ring bases) thymine cytosine uracil Purines (double-ring bases) adenine guanine. 1. 5C ribose/ deoxyribose sugar @ 1’ C , N-base covalently bonds @ 5’ C, phosphate bonds. DEHYDRATION. l inks them.

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NUCLEOTIDE MONOMER

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  1. NUCLEOTIDE MONOMER H 5 Pyrimidines (single ring bases) thymine cytosine uracil Purines (double-ring bases) adenine guanine 1 5C ribose/deoxyribose sugar @ 1’ C , N-base covalently bonds @ 5’ C, phosphate bonds

  2. DEHYDRATION links them http://www.youtube.com/watch?v=Udq7dX7jJMw

  3. HYDROGEN BONDS between bases pyrimidine with purine

  4. DESIGN & DIRECTION The helices are COMPLEMENTARY reflecting the base-pair rule The helices are the inverse of each other ANTI-PARALLEL read/replicated in opposite directions 5’ to 3’

  5. SEMICONSERVATIVE REPLICATION One strand from parent DNA conserved in each duplicate

  6. UNTWISTING the HELIX Cuts backbone to cope with over- or undercoiling of helix as replication fork moves TOPOISOMERASE: HELICASE: Untwists helix; Breaks H-bonds between base pairs DIRECTION OF REPLICATIONFORK

  7. SEQUENCING RNA primer into place; then nucleotides follow DNA polymerase adds free nucleotides to the growing chain RNA primer bonds with help of primase

  8. ENZYMES to BOND Ligase binds the sugars and phosphates, completes the strand DNA Polymerasecopies the code, binds the N-bases. Can only add to the 3’ end of the nucleotide

  9. DIRECTION MATTERS Nucleotides added only by bonding a 5’ C (phosphate group) to a 3’C of sugar (not vice-versa) ‘wrong’ direction Lagging strand Follows replication fork continuous construction Leading strand

  10. SOLUTION Lagging strand is built in fragments – Okazaki fragments – which are pasted in in sections http://www.wiley.com/college/pratt/0471393878/student/animations/dna_replication/index.html http://www.courses.fas.harvard.edu/~biotext/animations/replication1.swf

  11. ERRORS in REPLICATION Point mutation a nucleotide substitution Changes 1 amino acid in the polypeptide Frameshift mutations insertion or deletion of nucleotides Changes all amino acids ‘downstream’

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