T/f watson and crick concluded that purines has to pair with pyrimidines due to their width in the double helix
The correct answer and explanation is:
True.
Watson and Crick concluded that purines must pair with pyrimidines in the double helix due to the structural requirements for the DNA molecule to maintain a uniform width. In 1953, James Watson and Francis Crick published their famous double-helix model of DNA, which was largely based on X-ray crystallography data from Rosalind Franklin and Maurice Wilkins. One of the key insights was that for the DNA helix to have a consistent and stable width, a purine must pair with a pyrimidine.
Purines (adenine and guanine) have a double-ring structure, while pyrimidines (cytosine, thymine, and uracil in RNA) have a single-ring structure. If two purines were to pair together, the width of the helix would be too wide to maintain the optimal distance between the two sugar-phosphate backbones. Similarly, if two pyrimidines were to pair, the helix would be too narrow.
By pairing a purine with a pyrimidine, Watson and Crick were able to ensure that the width of the DNA molecule remained consistent and compatible with the X-ray diffraction patterns they observed. Specifically, adenine (a purine) pairs with thymine (a pyrimidine), and guanine (a purine) pairs with cytosine (a pyrimidine). This complementary base pairing mechanism is fundamental to DNA replication and transcription, as it allows the two strands of DNA to be copied accurately.
The discovery of base pairing also led to the understanding that DNA’s sequence of bases carries genetic information, which is translated into proteins through processes like transcription and translation. This pairing rule, now known as Chargaff’s rule, plays a vital role in the stability and functioning of DNA in all living organisms.