Cells 2

Now this differs with the type of cell. Some cells, like nerve cells, only divide seven to nine times in their total life. Others, like skin cells, will divide many, many more times. But finally the cells stop renewing themselves and they die. And in the cells of human body itself, in the cells of every organ, of almost every type of tissue in the body, the same thing will happen eventually. You know that all of persons' genetic information is contained on very long pieces of DNA called Chromosomes, 46 of them in the human cells. That's 23 pairs of these Chromosomes of various length and sizes. 

New Words and Expressions 

renew     复原/更新 

tissue    (生物）组织/纸巾 

eventually    最终/最后 

genetic     基因的 

chromosome    染色体 

various length and sizes    各种长度和大小