#2 Geneticist Review





Geneticist review

The Nobel Prize in Physiology or Medicine 1933

T.H Morgan

Thomas Hunt Morgan was born on September 25th, 1866.

His research group showed that genes are located on chromosomes, the two constituents of chromosome – proteins and DNA. Until the 1940s, the function of proteins was known to be the genetic material; however, this was not consistent with experiemtns with microorganisms, like bacteria and viruses.

Frederick Griffith started discovering the genetic role of DNA in 1928. He studied ‘Streptococcus pneumonia, a bacterium that causes pneumonia in mammals.

R Strain was Harmless, but S strain was pathogenic (causes disease).

He mixed heat-killed S strain with live R strain in his experiment and injected this into a mouse.

The mouse died due to the pathogenic strain in his blood. Griffith called this phenomenon ‘Transformation’, a change in genotype and phenotype due to the assimilation of a foreign substance (now known as DNA) by a cell.

Hershey & Chase experiment

American biologists Alfred Hershey and Martha Chase

determined what composed the genetic material of a

bacteriophages or just phages (viruses that specifically

attack bacteria). They knew that viruses consist of a

DNA (sometimes RNA) enclosed by a protective coat of

protein. A virus replicates by infecting a host cell. It takes

over the cell’s metabolic machinery.

Erwin Chargaff

His work and a series of rules based on a survey of DNA composition in organisms.

- DNA is a polymer of nucleotides (nitrogenous base, deoxyribose, a phosphate group)

- Bases of DNA are adenine, thymine, guanine or cytosine.

- Various DNA compositions from species to species.

- Any species has the four bases but not the same equal, ratios.

  

- His rule says there is a peculiar regularity in the ratios of nucleotide bases.
For example, % thymine = # adenine and % cytosine = guanine.










Maurice Wilkins & Rosalind Franklin

British physical chemists and expert in X-ray crystallography studied the structure of DNA.

They learned that the DNA was helical in shape and Rosalind Franklin (she) correctly deduced that DNA's phosphate subunits, or groups, are situated along the outer portion of the molecule. Although she initially found out the helical shape of DNA, she did not get awarded, because she died due to the exposure to radioactiviy.











Watson & Crick

They used the results from studies and X-ray diffraction data from Wilkins and Franklin to determine DNA’s molecular structure. By 1953, they had made the double helix structure of DNA which is commonly referred to as the Watson-Crick Model of DNA. Consequently, they were awarded a Noble prize in 1962.

If you like to know more about virsues, click below website.

http://www.accessexcellence.org/RC/AB/BC/Experiments_that_Inspire.php