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.\

Sample Solution