Why do electrons in a water molecule tend to be found circulating around the oxygen atom​

Suppose a scientist measures the amount of dna per cell of a particular diploid species at various stages of meiosis. she finds that the meiotic cells contain 3.7 pg , 7.3 pg , or 14.6 pg of dna. match each stage of the cell cycle to the corresponding amount of dna contained within a cell at that stage.

What are the doorways into and out of cells, attached to the membrane, and built in the rough er.

Why are scientists concerned about the depletion of the ozone levels in the stratosphere?