How does your DNA decide what you look like?
Ever wondered why you might have your dad’s nose but your mum’s hair? You get your unique mix of traits because your parents hand down instructions in the form of genes. These instructions are stored in your DNA and passed on when your parents’ cells combine to make you. This whole process of passing down genetic information is called
inheritance: when your parents’ DNA instructions are copied into the cells that make you, so you end up with a mix from both sides of your family
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The differences you notice between yourself and your friends (or even your siblings) are called variation. That’s why no two people (except identical twins) are exactly the same, even in the same family.
Why do you and your siblings look similar, but not like clones?
You and your siblings might have the same parents, but you’re not photocopies of each other. That’s because every child gets a random mix of their parents’ genetic instructions. During the formation of egg and sperm cells (thanks to a process called meiosis), the chromosomes are shuffled and split in new ways every time. Then, which sperm meets which egg is pure chance,like a lottery draw. This means you and your siblings each end up with a different combination of genes, even though you’re working with the same starting material.
Think of your parents’ genes like a playlist of songs. Each sibling gets a different shuffle, so everyone’s playlist (set of traits) is unique,even if the songs (genes) come from the same library.
Same parents means you’re working with the same set of possible genes, but the way those genes combine is always different. That’s why you and your siblings can look alike but never exactly the same.
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