DNA Deoxyribonucleic Acid Dr. Jim Bidlack University of Central Oklahoma Special thanks to John Wilson for providing the template of this presentation in partial fulfillment for Cell Physiology (BIO 4454) during the Fall 2002 Semester.

History of DNA Fred Griffith and the mouse experiment Fred Griffith Transforming “principle” Oswald Avery’s conclusion of DNA as the transforming principle Oswald Avery’s Isolation of DNA Watson & Crick’s Double Helix Watson & Crick’s Sugar, phosphate, base

Structure of DNADNA DNA is a double helix made of complimentary antiparallel strands DNA The backbone is constructed of a five carbon sugar and a phosphate group The rungs consist of the different bases held together by hydrogen bondshydrogen bonds

Structure of Nucleic Acids DNA is a five carbon sugar with two hydrogens on the second carbon RNA is a five carbon sugar with a hydrogen and hydroxyl group on the second carbon

Structure of the DNA Bases Two classes of bases: Purines and Pyrimidines Purines consist of Adenine (A) and Guanine (G) Pyrimidines consist of Thymine (T) and Cytosine (C) Bases are the same in RNA except that Uracil (U) is substituted for Thymine

Backbone Linkage Any nucleotide can be connected with a phosphodiester bond Nucleotides are triphosphated The 5’ ends with a phosphate and the 3’ ends with a hydroxyl The phosphate is attached to the 5’ carbon and the 3’ carbon of the sugar The bases are attached to the first carbon

DNA Linkage Helix is anti-parallel and complimentary Left side is from 5’ end to 3’ end Right side is from 3’ end to 5’ end A matches with T stabilized by two hydrogen bonds C matches with G stabilized by three hydrogen bonds

Replication is semi- conservative Replication Each strand is a template for another strand New DNA strands contain one new strand and one parental strand Bases on strands are complimentary (A w/ T & C w/ G) DNA Replication

DNA synthesizes in one direction, from the 5’ end to the 3’ OH end Many enzymes contribute in the replication of DNAreplication of DNA Helicases - unwind the DNA Topoisomerases - releases the tension Single Stranded Binding Proteins - maintain the single strands after unwinding DNA polymerases - add nucleotides and reads the template strand. There are five polymerases for mammals. Must have a 3’ OH end DNA polymerases

Summary DNA is a double helix with complementary anti-parallel strands DNA consists of sugar, phosphate and bases There are two classes of bases: Purines and Pyrimidines Nucleotides are connected by a phosphodiester bond Replication is semi-conservative from the 5’ end to the 3’ end and involves several enzymes