Question - What are the important features of DNA revealed by Franklin and Wilkins?
Answer -
The important features of DNA revealed by Franklin and Wilkins are as follows:
a. It has a helical structure similar to a spiral staircase.
b. The molecule has a diameter of 20 Å.
c. The distance between successive nucleotides is 3.4 Å.
d. The distance between successive turns of the helix is 34 Å, i.e. there are 10 nucleotides in every turn of the helix.
Later in the year 1950, Erwin Chargaff formulated important generalisation on the ratio of the different bases found in DNA.
These generalisations are referred to as Chargaff’s rules, which are as follows:
a. In a given DNA, the purines and pyrimidines are always in equal amounts, i.e. adenine (A) + guanine (G) = thymine (T) + cytosine (C).
b. The amount of adenine is always equal to that of thymine, and the amount of guanine is always equal to that of cytosine.
c. The sugar, deoxyribose, and phosphate occur in equimolar proportions
d. The ratio of A + T / C + G is constant for a species, which can be used to identify the source of DNA.
With these two lines of evidences explained above, Watson and Crick proposed the double helical structure of DNA and they were awarded the Nobel Prize for this discovery in the year 1962. They shared the award with Maurice Wilkins. The double helical structure could explain the two main functions of DNA, i.e. the autocatalytic and the hetero catalytic functions very convincingly.