NEET Botany Molecular Basis of Inheritance Questions Solved


How does replication of long DNA molecules occur? Explain the process.

(i) In long DNA molecules the two stands cannot be separated in its entire
    length as a large amount of energy is required for this process.

(ii) This replication occurs within a small opening of DNA helix known as
     replication fork.

(iii) DNA dependent DNA polymerase catalyses polymerisation of
     nucleotides only in one direction, i.e., 5' -> 3'.

(iv) One on stand with polarity 3' -> 5' the replication is continuous and on
      other with polarity 5' -> 3' it is discontinuous.

(v) The discontinuously synthesized fragments are later joined by the
     enzyme DNA ligase.

(vi) The replication does not initiate randomly at any point in DNA. There
      is a definite region in E.coli DNA where the replication originates . Such
      regions are termed as origin of replication.

(vii) Replication is a very expensive process. Deoxyribonucleoside
       triphosphate are used instead of nucleotides as they serve dual
       purposes. That is -
      * They act as substrate;
      * They provide energy for polymerisation reaction (The two terminal
         phosphates in a deoxyribonucleoside triphosphate are high energy
         phosphates as in the case of ATP).

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