WHY YOU ARE YOU

Inside both the sperm and ovum, there are thread-like structures called chromosomes. These are made up of units of material called genes, which carry the information that makes you different from anyone else. Genes help determine all your physical and mental characteristics – the shape of your nose, how tall you are and so on.

Genes also carry the information that decides which sex you are. Men have a pair of chromosomes in most cells, called X and Y. women have a pair called X and X. In the gametes ( the sex cells, sperm and ovum) there are only single chromosomes, and  the sex chromosomes will be either X or Y in the male cell, and just X in the female cell. When a sperm and ovum join, the chromosomes from each cell pair up. If a sperm cell carries a Y, it joins with the X in the ovum and a boy will be born. If the sperm has an X and joins with a X from the ovum, a girl will be born.

You don’t simply inherit your parents’ physical features; you also inherit features from previous generations which which may not have shown up in your parents( recessive genes). The gene for blue eyes is a recessive one. It does not take effect in combination with the brown-eyes gene, but only with another blue-eyes gene.