it is often useful for scientists to study a population of cells that are all at the same stage of the cell cycle. for example, the discovery of cyclins and cdks was enabled by studying frog eggs that divided synchronously after fertilization; extracts from the embryos were thus representative of the cell-cycle stage at which the extract was made. researchers have devised means to synchronize asynchronous populations of cultured cells. for example, serum starvation deprives cells of mitogens and blocks cells in the g0/g1 phase of the cell cycle. another method involves gently shaking culture flasks and harvesting the cells that release from the substratum. in what stage of the cell cycle are these cells most likely to be?