Question

regulation of cell cycle​

Answer 1

Cell cycle progression is regulated by the sequential activation and inactivation of CDKs. In somatic cells, movement through G1 and into S phase is driven by the active form of the Cyclin D1, 2,3/CDK4, 6 complex and the subsequent phosphorylation retinoblastoma (Rb) protein.

Answer 2

Animal development from a single-cell zygote to fertile adult requires many rounds of cell division. During each division, cells complete an ordered series of events that collectively form the "cell cycle". This cycle includes accurate duplication of the genome during the DNA synthesis phase (S phase), and segregation of complete sets of chromosomes to each of the daughter cells in M phase (Figure 1A). The somatic cell cycle also contains "Gap" phases, known as G1, which connects the completion of M phase to initiation of S phase in the next cycle, and G2, which separates the S and M phases. Dependent on environmental and developmental signals, cells in G1 may temporarily or permanently leave the cell cycle and enter a quiescent or arrested phase known as G0.