39. Difference between prokaryotic cells and Eukaryotic Cells along with diagrams?
40. Describe the Watson and crick model of DNA in detail?
Answers
Explanation:
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Answer:
40)J.D.Watson and F.H.C. Crick (1953) combined the physical and chemical data, and proposed a double helix model for DNA molecule. This model is widely accepted. According to this model, the DNA molecule consists of two strands which are connected together by hydrogen bonds and helically twisted.
Each step on one strand consists of a nucleotide of purine base which alternates with that of pyrimidine base. Thus, a strand of DNA molecule is a polymer of four nucleotides i.e. A, G, T, C. The two strands join together to form a double helix. Bases of two nucleotides form hydrogen bonds i.e. A combines with T by two hydrogen bonds (A = T) and G combines with C by three hydrogen bonds (G = C)
However, the sequence of bonding is such that for every ATGC on one strand there would be TACG on the other strand. Therefore, the two chains are complementary to each other i.e. sequences of nucleotides on one chain are the photocopy of sequences of nucleotides on the other chain.