Chapter 16
• Alfred Hershey and Martha chase answered the question whether protein or DNA was the genetic material by using Bacteriophages (viruses that infect bacteria). o Bacteriaphages were good for the experiment because they only contain 2 organic compounds, DNA and protein. • James Watson and Francis Crick were the first to solve the structure (structure=function) of DNA. • X-ray crystallography( process used to visualize molecules in 3-D. • DNA is a double helix- structure • The nitrogenous bases of DNA are( adenine (A), thymine (T), guanine (G), and cytosine (C). • The 2 strands (the leading and the lagging strand) are antiparallel. o The leading strand goes in direction 5’ to 3’. o Lagging strand goes 3’ to 5’. Takes longer to replicate cause it’s built in fragments. • Tip from the book(know these enzymes for replication: DNA polymerase, ligase, helicase, and topoisomerase. Know this enzyme for transcription(the role of RNA polymerase. • Replication(making DNA from already existing DNA strand. DNA replication is semiconservative (1/2 of original DNA and the other ½ is from new DNA strand). This is used by humans! o A group of enzymes called DNA polymerases catalyzes the elongation of new DNA at replication fork. The overall direction of DNA replication goes from the origin to the fork. o DNA polymerase adds nucleotides to the growing chain one by one; working in a 5’ to 3’ (DNA build strand (“new”) or RNA polymerase go 5’(3’ in the build strand). Parent strand DNA and RNA polymerase is 3’ to 5’. o DNA polymerase matches adenine with thymine and guanine with cytosine o The lagging strand is synthesized in separate pieces called Okazaki fragments (which segments in 3’(5’), which are then sealed together by DNA Ligase. Forming a continuous DNA strand. • Many factors in replication: o Base pairing in