The Egg That Became You Already Existed Before Your Mother Was Born

Updated: Jul 23

The story of your life began earlier than most people realize.

Long before you were born, your mother was developing inside your grandmother's womb. As she grew, her ovaries were already forming millions of immature egg cells. One of those tiny cells would eventually become the egg that, years later, helped create you.

That same egg cell remained inside your mother's ovary throughout her childhood. Years later, as part of her monthly cycle, it began the final stage of its maturation.

Inside that single cell were 23 pairs of chromosomes. One chromosome in each pair came from your mother's mother. The other came from your mother's father.

To see how this works, follow just one pair: chromosome 1, the largest of the twenty-three, and the one carrying the most genes.

Think of chromosome 1 as two reference books. Your mother inherited one version from each of her parents. Both books contain the same chapters, but each includes thousands of tiny differences in wording.

Before the egg was released, those two copies of chromosome 1 lined up side by side and exchanged matching sections of DNA. Imagine two nearly identical reference books trading a few pages with one another. Each book still tells the same overall story, but now each contains a unique mixture of information from both grandparents.

Biologists call this exchange crossing over. It reshuffles DNA into new combinations, a process known as genetic recombination.

When that process was complete, the egg received just one of those newly reshuffled copies of chromosome 1. Which chromosome ended up in the egg was entirely random.

The same process happened with chromosome 2, chromosome 3, and every remaining chromosome pair until the egg contained 23 chromosomes instead of 23 pairs.

Meanwhile, your father's sperm was being created through the same process. His chromosome pairs also exchanged matching sections of DNA before each sperm received one reshuffled chromosome from every pair.

When the egg and sperm met, they combined to form a single cell containing 46 chromosomes, arranged in 23 pairs.

At that moment, your genetic blueprint became unlike anyone else's who has ever lived.

That simple process is why brothers and sisters inherit different combinations of their parents' DNA.

It's also why grandchildren inherit different pieces of their grandparents' DNA.

Go back just ten generations and your family tree contains about 1,024 direct ancestors, even though only a fraction of them are still represented in your DNA.

Every ancestor is part of your family tree.

Only some are still represented in your DNA.

Read About The 23 Chromosomes That Help Make You You Here.