Passage 1

There are about 7 billion people in the world. But every person is unique. Every living thing is a unique combination of characteristics. Why is each living thing unique?
    Over 150 years ago, a scientist by the name of Mendel studied plants, especially pea plants. He wondered why each pea plant was of a certain color, shape and size.
    Mendel discovered that pea plants carried factors, and parents passed these factors onto their offspring. Today we call these factors genes.
    Genes are tiny pieces of matter that carry information from parents to offspring. Now we know that every person is unique. A major reason is that every person is a unique combination of genes.