WEBVTT - How children from the same parents look so different?

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<v Speaker 1>Welcome to brain Stuff from how Stuff Works dot com

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<v Speaker 1>where smart Happens, brought to you by Visa. We all

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<v Speaker 1>with today's question, how can children from the same parents

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<v Speaker 1>look so different? The DNA of the parents never changes,

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<v Speaker 1>so how can there be so much variation. It turns

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<v Speaker 1>out that there's a system specifically designed to make children different,

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<v Speaker 1>and we can explore that a little bit today. Every

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<v Speaker 1>person has a set of chromosomes. Each chromosome contains two

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<v Speaker 1>halves that join in the middle, so they look like

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<v Speaker 1>an X. All that a chromosome is, by the way,

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<v Speaker 1>is two very tightly coiled strands of d N A.

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<v Speaker 1>The two halves of each chromosome come from the two parents.

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<v Speaker 1>One half of the X in each chromosome comes from

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<v Speaker 1>the mother and the other half comes from the father.

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<v Speaker 1>The two halves are bonded together at the middle of

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<v Speaker 1>the X. Each half of the X contains a complete

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<v Speaker 1>set of genes, so each chromosome actually has two copies

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<v Speaker 1>of every gene, A sperm and an egg meat to

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<v Speaker 1>create a new person. The sperm carries one half of

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<v Speaker 1>the new person's ultimate chromosomes, and the egg contains the

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<v Speaker 1>other half. The question then comes down to where does

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<v Speaker 1>the DNA and the sperm and the egg come from.

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<v Speaker 1>A person has two of every gene, but when a

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<v Speaker 1>sperm gets formed or an egg gets formed, it will

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<v Speaker 1>only contain one of those two genes, but which one?

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<v Speaker 1>This is where nature does an especially amazing thing. When

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<v Speaker 1>forming sperm cells, the father's body randomly chooses genes from

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<v Speaker 1>the two halves of the father's chromosomes. This means that

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<v Speaker 1>every term cell contains a random mix of the father's

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<v Speaker 1>parents genes. The same thing happens when forming eggs. Therefore,

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<v Speaker 1>each child that a couple produces is a random mix

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<v Speaker 1>of the genes. That random mixing is why children are

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<v Speaker 1>so different. Do you have any ideas or suggestions for

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<v Speaker 1>this podcast? If so, please send me an email at

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<v Speaker 1>podcast at how stuff works dot com. For more on

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