DNA BUILDING BLOCKS OF LIFE HISTORY OF DNA

DNA: BUILDING BLOCKS OF LIFE

HISTORY OF DNA: EXPERIMENT 1 � Griffith (1928)- scientist hoping to learn why some bacteria caused illness, but not others

Transformation- process where 1 strain of bacteria is changed by genes of another strain of bacteria Concludes transforming factor are GENES! HISTORY OF DNA

HISTORY OF DNA: EXPERIMENT 2 � Hershey and Chase - wanted to know if viruses used DNA or proteins as their genetic material � Used bacteriophage- a virus that infects bacteria � Labeled virus proteins with radioactive sulfur, labeled virus DNA with phosphorus

Protein coat DNA BACTERIOPHAGE

HISTORY OF DNA: EXPERIMENT 2

HISTORY OF DNA: EXPERIMENT 2 � Conclusion: DNA is the genetic material found in genes in all living cells

SO WHAT’S DNA FOR? Storing Information The genetic material stores information needed by every living cell. *carry instructions to direct cells to become different

SO WHAT’S DNA FOR? Copying Information Before a cell divides, its genetic information must be copied. Transmitting Information When a cell divides, each daughter cell must receive a complete copy of the genetic information.

DNA = DEOXYRIBONUCLEIC ACID Found in the nucleus of the cell Deoxyribo- is referring to DEOXYRIBOSE which is…. .

COMPONENTS OF DNA � Made of repeating nucleotide subunits � Each contain a phosphate, sugar and base *4 types of nitrogenous bases: Purine (2 ring) Adenine (A) Pyrimidine Guanine(G) (1 ring) Cytosine(C) Thymine (T)

� THE � � NUCLEOTIDE BASE PAIRS Adenine Cytosine binds Thymine Guanine only DNA is made of two long chains of nucleotides joined by hydrogen bonds, forming a double helix G and C are complementary as are A and T

The two strands of DNA run in opposite directions (antiparallel)

� DNA is Complementary: bases on one strand match up with the bases on the other strand (A-T and G-C) � Example 1: Strand 1 - ATG GGC CTA Strand 2 - TAC CCG GAT Example 2 AGG Strand 1: GCC CTA TTA CGT Strand 2: CGG GAT AAT GCA

HOW THIS STRUCTURE WAS DETERMINED � Chargaff’s � ratio rule Rosalind Franklin: took a diffracted X-ray photo of DNA “X” is evidence DNA is twisting, forming a helix

Watson and Crick were clued by Franklin’s xray and it enabled them to build a model depicting DNA’s structure and properties, they won Nobel Prize