NEET BIOLOGY

Detailed explanation-1: -G1 is followed by S phase (synthesis), during which DNA replication takes place. The completion of DNA synthesis is followed by the G2 phase (gap 2), during which cell growth continues and proteins are synthesized in preparation for mitosis.

Detailed explanation-2: -DNA replicates in the S phase of the cell cycle and initiates at specific regions in the DNA sequence known as DNA replication ‘origins’. A number of proteins participate in DNA replication and the process is subject to scrutiny by cell surveillance mechanisms called cell cycle checkpoints.

Detailed explanation-3: -In S phase, the cell synthesizes a complete copy of the DNA in its nucleus. It also duplicates a microtubule-organizing structure called the centrosome.

Detailed explanation-4: -S phase is the period of wholesale DNA synthesis during which the cell replicates its genetic content; a normal diploid somatic cell with a 2N complement of DNA at the beginning of S phase acquires a 4N complement of DNA at its end.

Detailed explanation-5: -Once all of the DNA is replicated and the twin chromatids form, the cell transitions from the S phase to G2. The G2 phase features rapid protein synthesis and cell growth. During this time, the cell builds up its supply of a protein complex called the maturation promotion factor, or MPF.