Molecular Basis of Inheritance

1)  T.H. Morgan showed that genes are located on chromosomes through fruit fly experiments.  fruit flies have the scientific name Drosophila melanogaster.  Morgan arrived at the idea through comparisons in the phenotype of fruit flies and the research done by Mendel.  The traits skipped a generation in both cases.


2) Griffith discovered the genetic role of DNA in 1928.  Until then, the scientific community assumed that the protein carried the genetic code.  Discovery made through study of Streptococcus pneumoniae, a bacteria responsible for pneumonia.  in the experiment, dead pathogenic stains of bacteria (smooth) absorbed DNA material from harmless bacteria (rough) to function again and kill the mouse in experiment.
Transformation is the event where genotype and phenotype changes due to assimilation of DNA.

3)  Hershey and Chase did experiment on T2 Phage, a virus.  DNA and protein were stained respectively, and DNA of virus was confirmed to be found inside infected cell, not protein.
 4)  Chargaff developed series of rules based on observation of DNA.  There were four bases, adenine, thymine, guanine and cytosine.  They do not appear in equal ratio.  Equal % of adenine and thymine must exist, as well as equal % of guanine and cytosine.
5)  Wilkins and Franklin studied structure of DNA with X-ray crystallography.  Shot light through a crystal representation of DNA to get vague 3-D arrangement of DNA.  Light is diffracted upon leaving crystal.  Franklin did not receive proper recognition because she was female and was dead from cancer (overdose of X-Ray).

Example of X-Ray Crystallography

6)  Watson and Crick determined structure of DNA.  From data collected by Wilkins and Franklin, Watson arrived at double helix shape.  He determined the width of helix and space between bases.
There are minor groups and major groups in DNA.  Minor are shorter connections between bases, whereas major have longer connections between bases.  Hydrogen bonds connected two strands together.  Adenine and thymine would only form double bonds, and guanine and cytosine would only form triple bonds.