AP BIOLOGY

Detailed explanation-1: -G1 phase. G1 is an intermediate phase occupying the time between the end of cell division in mitosis and the beginning of DNA replication during S phase . During this time, the cell grows in preparation for DNA replication, and certain intracellular components, such as the centrosomes undergo replication.

Detailed explanation-2: -Also known as gap 1 phase, it is the first phase of the cell cycle in cell division. The cell is metabolically active and continuously grows in this phase of the cell cycle. However, no DNA replication takes place in this phase.

Detailed explanation-3: -In G1, cells accomplish most of their growth; they get bigger in size and make proteins and organelles needed for normal functions of DNA synthesis. Here, proteins and RNAs are synthesized, and, more especially the centromere and the other components of the centrosomes are made.

Detailed explanation-4: -DNA replication begins with the assembly of pre-replication complexes (pre-RCs) at thousands of DNA replication origins during the G1 phase of the cell cycle.

Detailed explanation-5: -During G1 phase, growth-dependent cyclin-dependent kinase (CDK) activity promotes DNA replication and initiates G1-to-S phase transition. CDK activation initiates a positive feedback loop that further increases CDK activity, and this commits the cell to division by inducing genome-wide transcriptional changes.