Question: Do the switches in the genes determine further changes as the organism develops such as whether it becomes blood, bone or muscle? Also I'm confused by what exactly causes the changes or mutations to code.

Hayley Lees answered on 28 Dec 2013:

Well, the simple answer to your first question is yes – but hopefully one of the other scientists will answer that in more detail in a bit while I try and explain the amswer to your second question 🙂

The reason why you are confused is because Alison didn’t reveal what causes mutations to happen (don’t worry, this may come up in the next two lectures…but hoepfully you will understand it after this 🙂 ).

Lots of things can cause changes or mutations to DNA. Do you know why it is important for us to wear suncream in the summer? Well, UV radiation from the sun can cause mutations – and too many mutations, in the wrong places, can be bad for you. Some chemicals can cause mutations too (things you would never dream of eating!). As well as things that our bodies are exposed to, some processes that happen inside our bodies can cause mutations. For example, inside our cells we have little factories called mitochondria that produce energy. Sometimes they make some other products, such as free radicals which can be cery danergous because they are highly reactive. And because they are so reactive, they can change or mutate our DNA!

There’s also something else that can happen to cause mutations. Everytime your body divides to make a new cell, it must make a copy of all of the DNA inside it. As Alison mentioned, DNA is millions and millions of letters long – if you had to copy that out with a pen and paper, I bet you would make a mistake somewhere. And this is what sometimes happens in our cells. A mutation or change can happen this way too.

Hope you are less confused now 🙂
Please ask again if you still need a bit more of an explanation.