Question

Many features of ------cells make them suitable for biochemical studies of the cell-cycle control system. For example, the cells are unusually large and are arrested in a -------- like phase. When the cells are triggered to resume cycling, the cell divisions have especially --------- G1 and G2 phases and occur ---------- . Studies with Xenopus eggs identified a partly purified activity called ------- that drives a resting Xenopus oocyte into M phase. MPF activity was found to be -------- during the cell cycle, although the amount of its kinase component, called ------- , remained constant. The regulatory component of MPF, called -------- , has a stimulatory effect on MPF activity and plays a part in regulating interactions with its ------ . The components of MPF are evolutionarily ------- from yeast to humans, so that the corresponding human genes are  to function in yeast.

able                             hexokinase                            short
asynchronously           inhibitory                       sperm
Cdk                             long                                       steady
conserved                    M                                        stimulatory
cyclin                           maturation promoting factor
substrate                     divergent                               oscillate
synchronously            egg                                        PI 3-kinase
ubiquitin                      fibroblast                               regulin
unable                         G1                                         S
uniform                  G2

Answer 1

Many features of egg cells make them suitable for biochemical studies of the cell-cycle control system. For example, the cells are unusually large and are arrested in a G₂ -like phase. When the cells are triggered to resume cycling, the cell divisions have especially short G₁ and G₂ phases and occur synchronously.

Studies with Xenopus eggs identified a partly purified activity called maturation promoting factor that drives a resting Xenopus oocyte into M phase. MPF activity was found to oscillate during the cell cycle, although the amount of its kinase component, called Cdk, remained constant. The regulatory component of MPF, called cyclin, has a stimulatory effect on MPF activity and plays a part in regulating interactions with its substrates.

The components of MPF are evolutionarily conserved from yeast to humans, so that the corresponding human genes are able to function in yeast.