What happens to the matter in an egg when it gets cooked ?

It's the proteins that cause the egg white to solidify when you cook it. If you keep the heat turned up too high or too long when you cook an egg, the proteins in the egg white form more and more bonds, squeezing some of the water out of the protein network and making the egg white rubbery.

b exhibiting favoritism toward the kikuyu people.

genetic variation can be caused by mutation (which can create entirely new alleles in a population), random mating, random fertilization, and recombination between homologous chromosomes during meiosis (which reshuffles alleles within an organism's offspring).