DNA: The Chemical Nature of the Gene Chapter 10

Chapter 10: Lecture Outline Historical perspective DNA structure RNA structure

Early historical perspective

We enter the 20 th century with an understanding of the DNA building block.

Some Experimental Data leading to DNA as biological source of DNA Griffith’s Avery et al. Hershey and Chase Chargaff Wilkins and Franklin Watson and Crick

Streptococcus pneumonia Smooth Strain Rough Strain

Griffith’s Experiment: 1928 Conclusion: A Transformation “factor” exists

1944: Avery;MacLeod;McMarty Discovered tranforming principle as DNA Oswald Avery

Heat killed; homogenize and filter IIIS virulent bacteria Destroy either RNA; protein or DNA Add samples to non-virulent bacteria Only bacteria without IIIS DNA did not transform Avery, MacLeod & McCarty

August 20, 2003 Martha Chase dies: With Alfred D. Hershey, she established DNA as the genetic material | By Milly DawsonBy Milly Dawson 1908 —

Support for nucleic acid transfer Hershey and Chase Experiment, 1952: Confirms DNA as genetic material

Conclusion: DNA identified as source of genetic information

At the same time amore detailed chemical Structure of DNA was also ongoing…

Franklin and Wilkins

Chargaff’s Rule

Watson and Crick, 1953 inferred the DNA structure

Nobel Prize:

Fraenkel-Conrat 1956: RNA also carries genetic information VIRAL RNA

Tobacco Mosaic Virus

The Structure of Genetic Material

The building blocks of DNA are nucleotides.

RNA’s SugarDNA’s Sugar

Nitrogenous Bases

DNA nucleotides

Polarity and Anti-Parallel

Back to Franklin and Wilkins Data: Pairing of specific classes of bases can account for diameter of DNA Just right! 6 sided ring 6 sided ring + 5 sided ring

Most Common Secondary Structure (3D structure) B-DNA Alpha Helix Right Handed Turn 10 bases per 360º turn

A function of Major and Minor Grooves

DNA ’ Special structures Modifications

Integration of DNA and RNA

Central Dogma Information Transfer