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The egg of every species of animal or plant carries a definite number of bodies called chromosomes. The sperm carries the same number. Consequently, when the sperm unites with the egg, the fertilized egg will contain the double number of chromosomes.

Although each egg cell produced by a woman carries a single X chromosome, the sperm cells produced by a man carry either an X or a Y. This means, in very simple terms, that the sperm cell determines a baby's sex.

Except for certain moments - when cells are dividing, for instance - chromosomes don't form compact, countable bodies inside cells. Instead, they unravel and flop about, which makes counting chromosomes a bit like counting strands of ramen in a bowl.

In cloning, in contrast, reproduction is asexual - the cloned child is the product not of two but of one.

People forget we come from an embryo and we're part sperm and part ovary. We have both sides in us.

My grandfather had two boys, my uncle had three boys, my dad had me and my two brothers, each of my brothers have had two boys. Then something happened with the chromosomal experiment and suddenly I've got three girls.

Each part of our genome is unique. We would not be alive if there was not a single mathematical solution for our chromosomes. We would just be scrambled goo.

From the beginning, each human embryo has its own unique genetic identity.

Closely related species of birds are also chromosomally similar.