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Molecular basis of Inheritance — BIOLOGY STD 12 Science — Question

Bihar BoardEnglish MediumSTD 12 ScienceBIOLOGYMolecular basis of Inheritance5 Marks
Question
(a) Explain the process of DNA replication in prokaryotes.
(b) Name the phase in the cell cycle in which DNA replication takes place in the cell. What if after DNA replication there is no cell division in a cell?
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Answer

(a) DNA Replication : DNA is the only molecule on earth which is capable of self-replication. It occurs during S-phase of the cell cycle when chromatin remain in extended form. During replication, the weak hydrogen bonds between complementary nitrogenous bases break thus separate and uncoil two polynucleotide strands of DNA molecule. Each strand act as a template for synthesis of new complementary strands. After the completion of replication, each daughter DNA molecule has one parental and one newly synthesized strand thus restoring 50% characteristics of parent DNA. This scheme of replication of DNA is known as 'Semi-conservative DNA replication'.
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(b) S Phase of Interphase
If cell division fails to occur after DNA replication in a cell cause mutations and chromosome rearrangements, leading to diseases or even can lead to death.

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