Activity: What your genes do

This week we will look at some of the ways your genes affect how your body is formed.

For this activity you will need

• A mirror
• Some other people. Try to get some who are related to you and some who are not.
• Paper
• Ruler
• Pen

What to do

1. Draw up a grid on your paper, with 9 rows and one more column than the number of people you have.
   • Down the side, label the rows person, tongue rolling, widow's peak, right-handed, freckles, right thumb, finger hair, bent pinky and free earlobes.
   • At the top, label the columns with the names of the people.
2. For each person, make a tick if they answer yes to these questions (there are photos of most of these on the web site if you aren't sure what they mean):
   • Can you roll your tongue?
   • Do you have a widow's point? A widow's point is when your hairline at the front comes to a point.
   • Are you right-handed?
   • Do you have freckles on your face, even only a few?
   • Clasp your hands together, with the fingers going between each other. Is your right thumb on top?
   • Is there hair between first and second knuckles on your fingers?
   • Hold your hands flat, with your fingers together. Does your pinky finger bend towards the other fingers, even slightly?
   • Your earlobe can hang loose or be attached. Is your earlobe loose?
3. Compare your results with other people.

What's happening

The traits we looked at all determined by our genes. You will probably find your results are more similar to your relatives than other people. This is because you have more genes in common with close relatives than with other people.

Genes are the instructions for how our bodies are made. Our genes are recorded in our DNA. If people have children, they pass on half their DNA to their child. A child inherits a complete set of DNA, one half from each parent.

Exactly how our bodies develop depend on the genes in our DNA, the conditions that we live in or a combination of both. For example, eye colour depends on genes. How tall you grow depends partly on your genes, but is also affected by how well nourished you are while you are growing. Some traits will also depend on a combination of genes, but the traits we tested for are all determined by a single gene.

Exactly how we inherit genes from our parents is a little complicated. Our genes actually contain two sets of instructions, one from each parent

• Sometimes these instructions agree with each other. For example, if the genes from both parents say "have a widow's peak" you will have a widow's peak.
• Sometimes they don't agree. For example, the genes you inherit from one parent might say "Have a widow's peak", while the genes from the other parents say "Don't have a widow's peak".

If our genes contain two sets of instructions, how does our body know which instructions to follow when they don't agree? It turns out that when they disagree, there is always one way that will win. For instance, if you have the "widow's peak" gene and the "no widow's peak" gene, you will always have a widow's peak. Having a widow's peak is called a dominant trait, while having no widow's peak is called a recessive trait. For a person to have a no widow's peak, both sets of instructions need to say "no widow's peak".

In the list of things we tested for, a tick shows a dominant trait, while no tick shows a recessive trait. For example, I have an attached earlobe, a recessive trait, which means I inherited the "attached earlobe" gene from both of my parents. I have a widow's peak, which means I inherited the widow's peak gene from one of my parents.

A person with both dominant and recessive genes can pass either one on to their children. This means that people can have traits that their parents don't have. For example, if both of your parents have the "Widow's peak" and the "No widow's peak" genes, they will both have a widow's peak, but if you inherit the "No widow's peak" gene from both of them, you won't have one. If you have ever heard of something like eye colour which "skips a generation", this is how it happens.

Our DNA records all of our genes, but there is also a lot of DNA that seems to record no useful information. This is sometimes called "Junk DNA". When forensic scientists create a genetic profile, they base it on junk DNA instead of DNA that contains genes. This is because the junk DNA can have a lot of variation, but the parts of DNA that record your genes only have a few variations (such as "widow's peak" and "no widow's peak"). Using DNA that has more variations means they can be more certain they have an accurate match.