Genes are found in all cells of the body. They're like chemical codes that determine a person's physical traits. Genes determine a person's height, skin color, eye color, blood type, and many other
things.
To see if people with the same genes had about the same intelligence levels, a group of scientists
conducted a study of 20 pairs of twins. Ten pairs were identical twins, both developing from the same
egg in their mother. The other ten pairs were fraternal twins. They were born at the same time but from
different eggs in the mother. Identical twins have almost identical sets of genes, but fraternal twins'
don't. After studying the 20 pairs of twins for 10 years, all of the individuals were given an intelligence
test. Scientists found that the intelligence scores of the identical twins were very close. Overall, the
test scores of the identical twins were much closer together than those of the pairs of fraternal twins,
1. What conclusion can you draw from the paragraphs?
2. List the main facts that helped you draw your conclusion.