question_answer

Directions : (1 - 5)

Read the passage given below and answer the following questions.

DNA as an acidic substance present in nucleus was first identified by Friedrich Meischer in 1869. He named it as 'Nuclein'. However, due to technical limitation in isolating such a long polymer intact, the elucidation of structure of DNA remained elusive for a very long period of time. Wilkin and Franklin, 1953 got very fine X-ray photographs of DNA. It was only in 1953 that James Watson and Francis Crick, based on the X-ray diffraction data produced by Maurice Wilkins and Rosalind Franklin, proposed a very simple but famous Double Helix 3D model for the structure of DNA. One of the hallmarks of their proposition was specific base pairing between the two strands of polynucleotide chains. However, this proposition was also based on the observation of Erwin Chargaff 1950 that for a double stranded DNA, the ratios between Adenine and Thymine and Guanine and Cytosine are constant and equals one. The base pairing confers a very unique property to the polynucleotide chains. They are said to be complementary to each other, and therefore if the sequence of bases in one strand is known then the sequence in other strand can be predicted. Also, if each strand from a DNA i.e., parental DNA acts as a template for synthesis of a new strand, the two double stranded DNA i.e., daughter DNA thus, produced would be identical to the parental DNA molecule. Because of this, the genetic implications of the structure of DNA became very clear.

DNA is

A) An alkaline substance

B) An acidic substance

C) Semi acidic substance

D) Semi alkaline substance