DNA: The Genetic DNA: The Genetic MaterialMaterial

Identifying the Genetic Identifying the Genetic MaterialMaterial Experiments of Griffith and Avery Experiments of Griffith and Avery

yielded results that suggested DNA yielded results that suggested DNA was genetic material (1944)was genetic material (1944)

Hershey & Chase Hershey & Chase used the used the bacteriophage T2 bacteriophage T2 and radioactive and radioactive labels to show that labels to show that virus genes are virus genes are made of DNA, not made of DNA, not protein (1952)protein (1952)

DNA stores information that tells cells DNA stores information that tells cells which proteins to make and when to make which proteins to make and when to make themthem

The Structure of DNAThe Structure of DNA

Discovered by Discovered by Watson & Crick in Watson & Crick in 1953 & received 1953 & received Nobel Prize in Nobel Prize in 1962 along with 1962 along with Maurice WilkinsMaurice Wilkins

http://www.youtube.com/watch?v=sf0YXnAFBs8&feature=autoplay&list=PL4900A106005340D0&lf=results_video&playnext=2

DNA DNA Polymer : Nucleotide Polymer : Nucleotide Monomer Monomer Each Nucleotide has 3 parts:Each Nucleotide has 3 parts: 1) 5 carbon sugar 1) 5 carbon sugar Deoxyribose Deoxyribose 2) Phosphate group 2) Phosphate group PO PO44

3) Nitrogen Base3) Nitrogen Base

Nitrogen Bases

Purines Pyrimidines

Adenine Guanine Thymine Cytosine

DNA forms a spiral DNA forms a spiral ladder ladder Double Helix Double Helix

Double helix is held Double helix is held together by weak together by weak Hydrogen bondsHydrogen bonds

Erwin Chargaff Erwin Chargaff DiscoveryDiscovery Chargaff’s Chargaff’s RuleRule A=T, G=C A=T, G=C

AA TT GG CC

HumaHumann

3030 3030 1919 1919

PlantPlant 2727 2727 2222 2222

VirusVirus 2121 2222 2828 2727

DNA ReplicationDNA Replication Phase of Cell Cycle? Phase of Cell Cycle?

Why replicate?Why replicate? Step 1: DNA Helicase Step 1: DNA Helicase

unzips DNA by breaking unzips DNA by breaking weak Hydrogen bonds.weak Hydrogen bonds.

Step 2: DNA Step 2: DNA polymerase adds polymerase adds nucleotides to exposed nucleotides to exposed nitrogen bases.nitrogen bases.

Step 3: Two DNA Step 3: Two DNA molecules form that are molecules form that are identical to original.identical to original.

DNA is referred to as “Semi-DNA is referred to as “Semi-conservative”, Each DNA molecule conservative”, Each DNA molecule 1 template & 1 new strand1 template & 1 new strand

DNA polymerase proofreads DNA DNA polymerase proofreads DNA during its replication so that very few during its replication so that very few errors occurerrors occur

http://www.youtube.com/watch?v=zdDkiRw1PdU

500/sec 500/sec bacteriabacteria

50/sec 50/sec humanhuman

EukaryotesEukaryotes

http://www.bing.com/videos/search?q=dna+replication+animation&mid=E308470BDBE4EA7925E3E308470BDBE4EA7925E3&view=detail&FORM=VIRE3&adlt=strict

http://student.ccbcmd.edu/biotutorials/dna/lag.html