Identical Twins?


Fred and Rita are in the library. Fred has to do a class presentation on genetics and DNA that afternoon.  He hasn’t done the work.

Fred:  Looking at the textbook Let’s see if I understand this. Fraternal twins share only 50% of their genes.

Rita: Like any brother and sister. But identical twins have the same DNA because they come from the same split egg.

Fred: They are basically the same person.

Rita:  Don’t be silly, Fred. No two people are exactly alike. We’re all different.

Fred:  Even when the DNA is exactly the same?
 
Rita:  That’s only until the egg divides.  After there are tiny gene mutations. Anyway, genes don’t explain everything. My cousins are identical twins but we can always tell them apart.

Fred: How?

Rita: It’s hard to explain. There are little physical things. And they have different personalities

Fred: But I read about this guy the police arrested in America. They did a DNA test and he was a perfect match. The problem was that the man had an identical twin brother.

Rita: So he accused his brother?

Fred: And his brother accused him. One was lying but they couldn’t prove it. They checked 100,000 DNA characteristics  – and there was not a single difference.

Rita:  They should have gone back to the old fashioned method.

Fred: What’s that?

Rita:  Fingerprints. Everybody has a different fingerprint.  She reads out this quotation
The pattern of our fingerprints is set up by our genes. Just like with other genes, though, the environment can change how we turn out.
While you were growing inside of your mother, you touched the amniotic sac. When you touched it during weeks 6-13, the patterns of your fingerprints were changed. This is why identical twins have different fingerprints.

Quick Check: True or False

1. Fraternal twins are not identical.
 2. Gene mutations create identical twins.
3. Every individual is different.
4. Fingerprints are affected by the environment
5. Your fingerprint changes before you are born.
Read about a recent 'wrong twin' murder case
Why 'identical twins genes are not identical'?
How police might approach identical twin DNA problem 

Quick Check: Answers 1.T  2. F 3.T 4. T 5. T