By the early 1900's it was known that the chromosomes carry the genetic (hereditary) information
Chromosomes consist of DNA (deoxyribonucleic acid)
Chemical Structure of DNA
Nucleotide:
1. Thousands of repeating units that make up the DNA (DNA is a polymer)
adenine, thymine, guanine, cytosine
The Watson-Crick Model of the Structure of DNA
DNA consists of two chains of nucleotides in a ladder-like structure which is twisted (Double Helix)
James Watson & Francis Crick:
Used data of M.H.F. Wilkins and Rosalind Franklin, early 50's
Wilkins and Franklin studied the structure of DNA crystals using X-rays.
The X pattern suggested the structure of DNA was a helix.
Used data of Erwin Chargaff, 1940's and early 50's
Chargaff's Rule: His data showed that in each species, the percent of A equals the percent of T, and the percent of G equals the percent of C.
Watson and Crick Model:
A. The sides of the ladder are made up of alternating molecules of phosphate and deoxyribose
B. The bases make up the rungs of the ladder
C. The bases that make up the rungs of the ladder are attracted by a weak chemical bonds called hydrogen bonds
Base Pairing Rule
Adenine (A) pairs with Thymine (T)
Guanine (G) pairs with Cytosine(C)
Order of Basis along one strand of DNA:
AGGTTACTGCAC
I give up :>
