How cells give shape to our body?

Question

I had a query from almost an year. How do cells of a part of our body, let's say hands, know in what shape to make the hand grow? For example how do the cells know that after the joint near wrist the hand needs to widen..? or how do the cells know how to make the face? in which direction to add the next divided cell after the zygote gets attached to uterus or even after that?

Answer 1

The answer to all of these questions is explained by the process of cell differentiation.

In the early life of a cell, it has the ability to become many different types of cells. The key to cell differentiation is DNA transcription. DNA transcription is the process through which DNA is converted into RNA. RNA is "read" by structures in the cell (ribosomes) to produce the proteins that "build" the cell, which is to say giving the cell its form and function. Think of the RNA as instructions for building something or a recipe. You'll end up with a different end result if the instructions are different. How do we end up with these different sets of instructions?

There are proteins that bind to the DNA which cause some regions of it to be transcribed more often and others not to be transcribed at all. So all cells have the same DNA, but not all of the DNA is transcribed into RNA. Remember a gene is a segment of DNA, and physically blocking this segment of nucleotides with proteins will prevent them from being copied in to the strand of RNA that's used to make proteins in the cell.

Many factors can affect which regions of DNA ultimately become transcribed. Cells can influence the development of other cells, and a major function of certain hormones in the body is to affect DNA transcription within cells.

There's much more to it, but hopefully this overview gives you a good general sense of the process.