Life: In the Making… Fertilisation

We used to think babies were hidden inside the sperm.

In almost every religion and every society, the world seems to revolve around babies. (Although sometimes it seems to revolve around bankers). As soon as someone is pregnant, everyone runs to them to feel the baby move. As soon as the baby is born, everyone runs to hold the baby, or to see it. Even in politics, education is one of the main standpoints, the education of children.

So I’m going to explain how these little people come about. I’m assuming I don’t need to start with the birds and the bees.So I’ll start with how everything I’ve talked about so far comes together, and fertilisation.

Remember DNA is the code of life, and remember how we create things using DNA. This is very similar.

A baby is essentially, a mix of its parents DNA. This mixed DNA makes the baby unique (as it is half one parent, and half the other, but not the same as either) and it also gives the baby a code for its own life. Using this new and unique code, the baby can start to make proteins, and form its own body. But there are a couple of hurdles to get over first.

The first is how we put the DNA together, which we do through gametes (the egg and sperm cells).

What essentially happens is that a cell starts to divide so that it can make these eggs and sperm. In normal circumstances this would mean that the DNA would unzip, it would make a copy of itself, and these copies would be put into the new cells. But this is a special form of division (meiosis) where the DNA does not replicate. In fact it more or less stays unzipped and is then pulled into a new cell (a gamete). What we end up with are cells with only half the DNA that they need.

It needed to be said.

The next stage is simple. The hopeful couple will use their extensive knowledge of the birds and the bees, somehow the sperm ends up inside the woman. The woman’s egg starts rolling about towards the sperm as they swim towards the egg and they meet somewhere in the middle. This sperm invades the egg, and the DNA from the sperm will then combine with that of the egg, making one complete set of mixed up DNA. Thus a baby is born.

I love the music you get in these vids.

Leave a comment


  1. There might be a couple of dodgy bits of language use in there…

    1) “…the baby can start to make proteins…” Isn’t it the proteins that make the baby? I know that sounds pedantic but I do notice quite a lot of science writing that personalises our molecular origins – origins that are, according to science, strictly impersonal. This seems to me to risk mixing science with animism (You’re in good company, though – Matt Ridley in his ‘Genome’ personalises DNA to such an extent you could imagine it having its breakfast each morning!).

    2) “This sperm invades the egg…” – the video provides a nice counterpoint to that: not many invasions involve a bunch of flowers! I think I’ve even heard it said somewhere that there’s evidence the egg chooses which sperm to let in.

    • I guess I was kind of talking from the angle that the single cell, with it’s DNA is the baby. By being able to make proteins it can increase it’s number of cells. The initial proteins are made by the parents. It’s kind of a chicken and egg scenario, where the egg comes first (kind of).

      On the second bit… Yea the area becomes a whole new kind of complex. There are hundreds of mechanisms dedicated to killing off weak and unsuitable sperm. The egg really has a choice of the best sperm when they finally reach it. And yes it probably still doesn’t make it easy for them.

      There was a great BBC programme on this (Inside The Human Body) there might be snippets of it around on the internet.


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: