Chromosomes

Chromosomes are tiny parts inside the cells of living things. They hold the plans that tell your body how to grow. These plans are written in a code called DNA. Without chromosomes, cells would not know what to do.

What Chromosomes Look Like

Chromosomes are so small you need a microscope to see them. When a cell is ready to split, chromosomes look like the letter X. They are made of long strings of DNA wound up tightly. Each chromosome holds thousands of little instructions called genes. These genes decide things like your eye color.

How Many We Have

Humans have 46 chromosomes in most of their cells. That means 23 pairs. You get 23 from your mom and 23 from your dad. Different living things have different numbers of chromosomes. A dog has 78, and a goldfish has 94.

Fun Facts

• If you stretched out all the DNA in one cell, it would be about 6 feet long.
• Some ferns have over 1,000 chromosomes.
• Chromosomes were first seen under a microscope in the 1800s.

Did You Know?

Boys have one X and one Y chromosome, while girls have two X chromosomes.