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Why aren’t we all one type of sex?

Why aren’t we all one type of sex?
Tom Morgans from Swansea (Age 5-14)

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One Response

  1. In animals the DNA in our cells is bundled up into chromosomes. In each cell we have two matching sets of these chromosomes which means that we have two copies of every gene that controls the way we look and function.

    When animal reproduce the new animal needs to be made up of cells containing two sets of chromosomes too. There are two ways to do this. One is to clone and make new animals from cells that already have two sets of chromosomes. Some animals can do this, such as flatworms that can be cut in two and grow the new halves or aphids where females already have lots of new tiny aphids, clones of themselves, inside them when they are born and don’t need male aphids to make them. The problem with this is that if there is damage to the chromosomes that might lead to disease or other problems this gets passed on to all the new animals. Damage can occur throughout life so the quality of the DNA may get worse.

    A different way animals reprpoduce is to make cells with only one set of the chromosomes. This is what we do. the female will make one kind, the egg, the male another kind, the sperm, and when they combine they make one big cell with the full two sets of chromosomes. When the eggs and sperm are being made genes can be taken from either of the parents’ sets of chromosomes so they get mixed up and then when the egg and sperm combine the genes can get mixed up again. This is why we look different from our parents. This also means that faulty genes can be taken out during the mixing and that new and sometimes better genes can be added. So having two different types of sex means we have a better chance of having healthier children than if we only had one type of sex and had to clone ourselves to make children.

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