Twenty-five years ago, I heard people said computers were stupid. They said so because computers just knew only one & zero (high & low voltages) and did what we asked them to do. Now I no longer hear that; what I hear now is that computers are smart, faster and faster. Of course they have to be smarter and faster because of millions human brains in there. Some suggest that someday computers may take over the world and no longer listen to us like a movie called I-Robot. Who knows! It could be. But for now, computers are our best friends. They tremendously help us. Imagine if there are no computers, how our life will be? Thus what are computers? How do they work?

That is what researchers said. What make them to say that? And based on what?
Before answering these questions we need to know three things: DNA, Y chromosome, and mtDNA.
We know that our body is made up of cells, and in fact our human body has about 100 trillions cells. In the center of each cell, nucleus, there are 23 paired chromosomes. Each pair chromosomes are half from father and other half from mother. The last paired chromosomes (23rd pair) are called sex chromosomes; XX is in female and XY is in male. Only male child carries Y chromosome from the father, and female child does not. Thus the father determines the sex of a child. Each chromosome is made up of a string of DNA (Deoxyribonucleic Acid), which is in turn made up of genes. Genes determine the traits (characters) of a person (heridity). One of the DNA functions is to pass that genetic information from parents to the child.