Hi Can i get a brief summary of what each of these individua

Hi,

Can i get a brief summary of what each of these individual did that contributed to the study of biology?

Avery, McCarty, McClead, Edwin Chargaff, Watson, Crick, Pauling

Solution

Avery, McCarty, McClead: The Avery–MacLeod–McCarty experiment was an experimental demonstration, reported in 1944 by Oswald Avery, Colin MacLeod, and Maclyn McCarty, that DNA is the substance that causes bacterial transformation, in an era when it had been widely believed that it was proteins that served the function of carrying genetic information.

Pneumococcus is characterized by smooth colonies and has a polysaccharide capsule that induces antibody formation; the different types are classified according to their immunological specificity.

The purification procedure Avery undertook consisted of first killing the bacteria with heat and extracting the saline-soluble components. Next, the protein was precipitated out using chloroform and the polysaccharide capsules were hydrolyzed with an enzyme. An immunological precipitation caused by type-specific antibodies was used to verify the complete destruction of the capsules. Then, the active portion was precipitated out by alcohol fractionation, resulting in fibrous strands that could be removed with a stirring rod.

Chemical analysis showed that the proportions of carbon, hydrogen, nitrogen, and phosphorus in this active portion were consistent with the chemical composition of DNA. To show that it was DNA rather than some small amount of RNA, protein, or some other cell component that was responsible for transformation, Avery and his colleagues used a number of biochemical tests. They found that trypsin, chymotrypsin and ribonuclease (enzymes that break apart proteins or RNA) did not affect it, but an enzyme preparation of \"deoxyribonucleodepolymerase\" (a crude preparation, obtainable from a number of animal sources, that could break down DNA) destroyed the extract\'s transforming power.

Edwin Chargaff: Chargaff discovered two rules that helped lead to the discovery of the double helix structure of DNA.

The first rule was that in DNA the number of guanine units are merely equal to the number of cytosine units, and the number of adenine units are merely equal to the number of thymine units. This hinted at the base pair makeup of DNA.

The second rule was that the relative amounts of guanine, cytosine, adenine and thymine bases varies from one species to another. This hinted that DNA rather than protein could be the genetic material.

Pauling: He proposed hydrogen bond concept. According to him, the two dna helixs are tied up with hydrogen bonds.

Watson, Crick: The discovery in 1953 of the double helix, the twisted-ladder structure of deoxyribonucleic acid (DNA), by James Watson and Francis Crick marked a milestone in the history of science and gave rise to modern molecular biology, which is largely concerned with understanding how genes control the chemical processes within cells. In short order, their discovery yielded ground-breaking insights into the genetic code and protein synthesis