Progression of cells through the division cycle is regulated by both extracellular (environmental) and internal signals that monitor and coordinate processes during phases of cycle. a) True b) False

In the experiment of cell fusion, when tumor cells were fused with normal cells, the initially formed tetraploid cells (or subsequently arising sub-tetraploid cells) were discovered to have lost the ability to form tumors. What is the explanation for this observation?

Q37

In normally dividing cells, once chromosomes have been properly segregated via the steps of mitosis, the two resulting “daughter cells” separate. In animal cells (and other cell types without a cell wall) the contractile ring plays a crucial role in the process of cytokinesis. Exactly how the contractile ring is accurately positioned, so as to be located midway between the two poles (ends) of the dividing cell, is still not fully understood, although factors released from the mitotic spindle are thought to play a role.Regardless of the precise positioning mechanism, one key player in the assembly of the contractile ring is the GTP/GDP binding protein Rho. In its active form, Rho can stimulate the activity of the actin-binding protein formin and (via effects on the myosin regulatory light chain) that of myosin II. Given their respective roles, why might activation of formin and myosin II be beneficial as cells assemble a functional contractile ring structure?