A recipe, copied twice
Why Do You Look Like Your Parents?
You got one copy of the instructions from each parent, shuffled into a combination nobody has had before.
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Step 1 of 5
Every cell carries a written instruction set.
Coiled inside almost every cell is a long chemical text that describes how to build and run a body. Copies of it go into egg and sperm cells.
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Step 2 of 5
You get exactly two copies of each instruction.
One from each parent. For most traits the two copies are consulted together, which is why you can resemble both parents at once.
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Step 3 of 5
Some instructions shout over others.
When the two copies disagree, one version can mask the other completely. A trait can sit silently in a family for generations and then reappear.
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Step 4 of 5
The copies are shuffled before they are passed on.
When egg and sperm cells are made, the pairs are cut and swapped. That is why two siblings get different halves of the same two parents.
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Step 5 of 5
Instructions are not the whole story.
Food, sleep, sunlight and exercise all change how a body turns out. Height and skin colour are the recipe and the cooking together.
Identical twins start from one shuffled set, which is why they look so alike — and why their differences are so interesting to scientists.
The short version
You carry two copies of every instruction, one from each parent, shuffled into a set nobody has had before and then shaped by your life.
Try it yourself
Check who in your family can roll their tongue into a tube. The pattern often skips a generation.
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