Question

Why is RNA necessary to act as a messenger? Why can't the code be taken directly from the DNA? How do some cells become brain cells and others become skin cells, when the DNA in ALL the cells is exactly the same? In other words, if the instructions are exactly the same, how does one cell become a brain cell and another a skin cell?

Answer 1

RNA is necessary to act as a messenger because it helps in encoding the message coming from the DNA to form proteins. The code can not be taken from the DNA because the DNA is too big to go through the nuclear pores. Some cells become brain cells as others become skin cells because of gene expression. Gene expression is the process by which a gene gets turned on in a cell to make RNA and proteins. Though every cell in a person’s body has the same DNA skin cells are haploid, and brain cells are diploid.

Hope this helps

Answer 2

In other words, if the instructions are exactly the same, how does one cell become a brain cell and another a skin cell? it has the ability to turn off genes. ... a cell grows, prepares for division, and divides into two new cells which are called daughter cells.