To accompany “Some identical twins don’t have the exact same DNA”

SCIENCE

Before Reading:

1.  What’s the main difference between fraternal and identical twins?

2.  What explains why “identical” twins usually look identical?

During Reading:

1.  What are monozygotic twins?

2.  What’s the difference in how these and dizogotic twins develop?

3.  Why have many genetics studies recruited identical twins as their subjects?

4.  In the past, to what had scientists attributed any genetic differences in identical twins?

5.  In the new study, how many twins were truly identical down to the genetic level?   

6.  How greatly did some of the other twins vary, genetically?

7.  What are mutations?

8.  To what do scientists now attribute those mutations? For instance, when did they likely occur?

After Reading:

1.  On a percentage basis, what share of twins in the new study were genetically identical? What share had more than 100 genetic differences? Show your work.