FINAL - LECTURE 11 Flashcards
Frederick Griffiths in 1928 demonstrated
the existence of
a “transforming principle” that changed the genotype of
Streptococcus pneumniae.
(a nonvirulent strain was tranformed to a virulent genotype)
Oswald Avery, Colin MacLeod and Maclyn McCarthy:
purified the transforming principle (griffiths) and showed that it was DNA
Alfred Hershey and Martha Chase
published experimental results that independently indicated that DNA was the genetic material
used radioactive isotopes of phosphorous and sulfur to label components of T2 phage
Erwin Chargaff had made a very significant observation
in measuring the nucleotide base composition of
DNA from different species.
The % A C G and T in the DNA from different species was
different.
But the % A always is equal to the % T and
the % G is always equal to the % C.
Chargaff’s rules: A=T and G=C
James Watson and Francis Crick:
worked with the X-ray
diffraction data of Rosalind Franklin
and Maurice Wilkins to propose the
double helix structure of DNA.
The structure of DNA presents a mechanism to account for 3
key functions of genetic material:
1.Complex information storage
2.Replication
3.Potential for mutation
What is the backbone of DNA made of?
Deoxyribose-phosphodiester
backbone
What are the two strands of DNA binded by?
hydrogen bonding
each strand of the diouble helix is composed of:
atoms bound by COVALENT bonds
The two strands of the double helix are held together by:
hydrogen bonds
Mathew Meselson and Franklin Stahl tested:
the models of replication
Messelson and Stahl’s
data showed that
DNA is replicated
semi conservatively
A-T bonding between opposite strands involves __ hydrogen bonds
2
G-C bonding between opposite strands involves __ hydrogen bonds
3
To demonstrate the DNA is the genetic material, Herschey and Chase conducted experiements using bacteria E. Coli ad bacteriophage T2. Only the bacteria …
That had been infected by the virus with radioactive DNA were radioactive
