GENETIC INHERITANCE

HERSHEY AND CHASE

  1. To determine whether viruses were either proteins and DNA.

  2. Provided evidence that DNA is genetic material.

  3. Discovered that:

    1. The non-genetic portion of the virus remains outside the cell
    2. An infected cell then manufactures large numbers of new viruses and bursts, releasing them to the environment
    3. Viruses are often specifc to a certain cell type

ROSILAND FRANKLIN

  1. Investigated the structure of DNA by X-Ray diffraction.
  2. Franklin had already become skilled in techniques of crystallography and X-ray diffraction while researching other carbon compounds at an institute in Paris.
  3. Rosalind Franklin’s X-ray diffraction provided crucial evidence that DNA was a helix.
  4. Franklin had obtained the sharpest X-ray diffraction images of DNA in existence.

WATSON AND CRICK

  1. Proved that DNA structure suggested a mechanism for DNA replication.
  2. One of Watson and Crick’s frist models had the sugar-phosphate strands wrapped around one another with the nitrogen bases facing outwards.
  3. Watson and Crick found the tight packing they were looking for would occur if a pyrimidine was paired with a purine and if the bases were “upside down” in relation to one another. In addition to being structurally similar, adenine has a surplus negative charge and thymine has a surplus positive charge so that pairing was electrically compatible.
  4. Discovered double helix structure.

ERWIN CHARGAFF

  1. Erwin Chargaff found that in DNA, the ratios of adenine (A) to thymine (T) and guanine (G) to cytosine (C) are equal.
  2. Chargaff discovered that in DNA from any source the amount of T was equal to A. Also, the amount of C was equal to G.

MESELSON AND STAHL

  1. Meselson and Stahl obtained evidence for the semi-conservative replication of DNA.
  2. Meselson and Stahl devised a new method of separating DNA containing 15N in its bases from DNA with 14N.