Thank you very much, Writeacher for checking my paragraph.

Question

Here is the last part.

1) Six months after being diagnosed with cancer, she was dead. HeLa cells have had a fundamental importance in scientific research.
2) Her living cells, which survive to this day have contributed to the study of cancer, have helped in developing the polio vaccine, and have allowed scientists to determine the effects of the atom.
3) They have also led to important advances in vitro fertilization, cloning, and gene mapping.
Actually, it is estimated that there are tons of these scattered cells in laboratories throughout the world.
4) HeLa has been bought and sold by millions of researchers in the decades earning hundreds of millions of dollars for the medical industry.

Answer 1

1) Six months after being diagnosed with cancer, she was dead. HeLa cells have had fundamental importance in scientific research. [delete 'a' before 'fundamental']

2) Her living cells, which survive to this day, have contributed to the study of cancer, have helped in developing the polio vaccine, and have allowed scientists to determine the effects of the atom. [I added one comma.]

3) They have also led to important advances in vitro fertilization, cloning, and gene mapping.
Actually, it is estimated that there are tons[<~~really? tons??] of these scattered cells in laboratories throughout the world.

4) HeLa has been bought and sold by millions of researchers in recent decades, earning hundreds of millions of dollars for the medical industry. [changed one word]