a Y and an X chromosome and it will become a male. But exactly what happens in the womb to make a boy or a girl? This interactive feature illustrates the astonishing changes that occur during the ...

Imagine you look in mom’s cell-free DNA and you find a bunch of Y chromosomes. The baby will be a boy, right? If you don’t see any Y chromosomes, a girl. Similarly, a fetus with Down Syndrome ...

Females (XX) carry twice as many X-linked genes on their sex chromosomes as males (XY). How do cells control gene expression to manage this potentially lethal dosage problem? A prime example of X ...

Mixed-gender twins are the most common type of fraternals, some 50 percent are boy-girl. To understand this combination: Males have XY chromosomes, females have XX chromosomes. You have a girl ...

The genetic information within each of these daughter cells is identical. A human cell contains 46 chromosomes. To simplify our illustration, we'll show only four. Though the genetic code of a ...

A chromosome is a single, long molecule of DNA. These highly organized structures store genetic information in living organisms. Small sections of the chromosome, called genes, code for the RNA ...