Question

If the instructions are exactly the same, how does one cell become a brain cell and another a skin cell?

Answer 1

Hint: The fundamental physical and functional unit of heredity is a gene. The genes consist of DNA. Some genes serve as instructions for creating protein-called molecules. Many genes do not code for proteins, however. In humans, from a few hundred DNA bases to more than 2 million bases, genes range in size.

Complete answer:
Both brain cells and skin cells contain DNA molecules, and the same genetic information is found in their DNA molecules. Gene regulation is the process of regulating which genes in a cell’s DNA are expressed. Different cells in a multicellular organism can express very different sets of genes, even though they contain the same DNA. The set of genes expressed in a cell decides the set of proteins and functional RNAs it contains, giving it its special properties.

Every cell in our body contains the same genes for the most part, but some genes are active within individual cells while others are not. They are capable of producing proteins while genes are involved. This mechanism is called gene expression. Genes which are inactive are silent or unavailable for protein development. Because of this reason even having the same instructions one cell becomes a brain cell and another a skin cell.

Note: - The theory of cells was a theory proposed in 1839 that cells together make all living organisms. Theodor Schwann and Matthias Jakob Schleiden built it.
- Since genes are short segments of DNA, not all DNA is made up of genes. Genes make up just 1-3 percent of the total DNA. A person’s genes' function is regulated by the rest of his/her DNA.
- DNA is closely coiled within a cell, so if all the DNA molecules in your body were connected end to end, it would stretch over 600 times from the Earth to the Sun (100 trillion times six feet divided by 92 million miles).