Some E.coli. mutants contain defective DNA ligase. When these mutants are exposed to 3H-labeled thymine and the DNA produced is sedimented on an alkaline sucrose density gradient, two radioactive bands appear. One corresponds to a high molecular weight fraction, the other to a low molecular weight fraction. Explain.
It can be due to defective DNA ligase, DNA ligase helps in joining DNA fragments to one another after replication such as okazaki fragments of lagging strands. If DNA ligase is defective these fragments stay disconnected which results in instability of other parent strand and hence new developed strand break downs in fragments while continuous strand remains, this led to appearence of two bands with small and large molecular weight.
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