Does a Embryo cell or a Somatic cell divide faster?
During the first several divisions, cells in an embryo divide very fast. This is because the only thing they need to do is make a copy of their DNA in preparation for division (during this phase, they exclusively use maternally derived proteins and mRNA — those that were present in the unfertilized egg). During this phase, all cells divide by cleavage, which means that one cell is split down the middle to make 2 cells, each half the size of the original cell. Also during this phase, the embryo does not grow in size. Eventually, the cells start to transcribe their own DNA and make their own proteins and the total embryo starts to grow and the cells begin to differentiate (they commit to becoming certain types of cells). At this point, the divisions take longer (but are still quite rapid). Many somatic cells in an adult organism do not divide, and those that do are tightly regulated by various mechanisms. Even in the fastest dividing cell in an adult, it takes about a day to complete a
