Unit 4: DNA & Protein Synthesis Ch 9: Chemistry of the Gene DNA = Deoxyribonucleic Acid

Video: Biologix: Development of Molecular Genetics Biologix: Development of Molecular Genetics How did each of the following scientists contribute to our knowledge of DNA and the genetic code? –Friedrich Miescher –Frederick Griffith –Oswald Avery, Colin MacLeod, & Maclyn McCardy –Alfred Hershey & Martha Chase –P.A. Levine –Erwin Chargaff –Rosalind Franklin & Maurice Wilkins –James Watson & Francis Crick

DNA is a polymer… What is the monomer that bonds to form DNA?

nucleotide Purines (1,2) Pyrimidines (3,4) A Model of DNA Nucleotide –phosphate + sugar + nitrogen base Alternating sugars & phosphates (“backbone”) Nitrogenous bases (“rungs”) –Pairs held together by hydrogen bonding –Gives name to nucleotide

A Model of DNA 4 kinds of nitrogen bases: –Purines (2 rings) Adenine Guanine –Pyrimidines (1 ring) Thymine Cytosine Always pair –A – T –G – C

A Model of DNA DNA molecule –2 chains of nucleotides bonded together shape = “double helix” –Similar to a rope ladder wrapped around an invisible pole DNA Structure Video

DNA is contained in chromosomes sugar-phosphate “backbone” & nitrogenous base “rungs”

DNA Replication Another word for replication??? Why must DNA replicate? When does it replicate? Where does it replicate?

How does DNA replication occur? –1. “Helicase” enzyme causes DNA molecule to unzip along H bonds DNA Replication

–2. “DNA polymerase” enzyme catalyzes synthesis of new DNA strands using the original strands as templates. Brings nucleotides from cytoplasm to pair with base on “parent” strand & form daughter strand –Ex. If have “C” base on parent strand  DNA polymerase brings nucleotide with “G” base DNA Replication

–3. Now have 2 new exact copies of the original molecule… so that when cell divides each daughter cell has an exact copy. DNA Replication

DNA Replication Video T C

Predict the next base…

Finish the replications…