How does our DNA relate to our personality and appearance? — Emma, age 9, Sydney
Hi Emma. Thank you for this great question!
Our body is made up of trillions of cells, each of which has a nucleus that holds our DNA.
Our DNA is made up of more than 20,000 genes. You can think of genes as the the instructions which help decide what we look like, how our bodies work and even our personalities.
We get half our genes from our biological mother and the other half from our father. That’s why we don’t look exactly like our parents, but we may look a bit like them — and may also think and act similarly to them.
That said, each of us still has a unique collection of genes overall. That means no two people carry exactly the same genes, not even brothers and sisters. And that’s why each of us has a unique appearance and personality.
What do our genes decide?
Our genes help explain many parts of our appearance, like how tall we are and the colour of our eyes.
They also have a hand in our other skills, such as how fast we can run, how good we are at solving problems, and whether we enjoy talking to new people (rather than if we feel shy).
By studying a person’s genes, scientists can tell whether that person is more likely to have blue or brown eyes, without even seeing them.
They may also be able to tell that person how likely they are to develop certain medical conditions later in life, such as cancer or myopia (when you can’t see far-off objects as clearly).
Read more: Curious Kids: Why do people get cancer?
Not everything is determined by genes and DNA
Although genes are important, they’re not the only reason for why we look, think, feel and act as we do — or why we’re more likely to have certain diseases. While some traits such as eye colour are mainly determined by our genes, an eye injury can change someone’s eye colour.
Our habits, such as how much we eat and exercise, also have a big impact on who we are and what we look like. If you eat too much junk, you’ll probably get chubby and start running slower, regardless of the genes your parents gave you.
Our environment at home, school and/or work play a key role in shaping us, too. Take myopia. Before the discovery of the more than 400 genes for myopia, scientists noticed children are at least three times more likely to be myopic if either one or both parents are. They realised if someone has trouble seeing far-off objects, there’s a decent chance this is related to genetics.
At the same time, however, there is currently a surge in myopia happening around the world, with more people becoming myopic even though their parents are not!
Researchers discovered our environments and habits play a huge role in myopia development. For instance, they found myopia (and the need to wear glasses) is more likely to happen among people living in cities rather than the country, and those who spend less time outdoors.
The way we perceive colour is also influenced by both our genes and environment. You might remember the social media trend of #thedress that went viral back in 2015.
The world was torn over whether the dress (below) is actually blue and black, or white and gold. Researchers later found the way we see colour in this dress is 34% related to our genes and 66% linked to environmental factors.
Read more: Curious Kids: why are people colour blind?
Genes and personality
“Personality” describes the relatively stable ways in which people think, feel and act. And again, genes do a pretty good job of explaining why some people are more outgoing and energetic, while others tend to be more moody and anxious.
Our genes also help explain how smart we are. But one surprising finding is our genes have more of an effect on us as we age. Among children, about 40% of the differences in intelligence scores are explained by genes. In young adults, this increases to about 60%, even though it’s the same genes that continue to affect intelligence.
This is most likely because our genes can impact which environments we prefer, and adults often act on their preferences.
For example, most adults do not get told when to go to bed at night! And adults who enjoy learning new things can choose to spend their time in libraries and art museums, or taking classes. In other words, adults can choose the environments and activities that best express their genes.
The future is in your hands
You can think of your genes as a way to understand yourself — but not as a way to make decisions. For example, just because someone’s parents may not have been able to go to university, they themselves can if they study hard.
Or, a person’s parents may be overweight, but that doesn’t mean they have to be. They can still join a sprint team if they’re willing to put in the effort.
Even though your DNA and genes shape a lot of your personality and appearance, remember: they do not determine your life story.