Humans have 23 pairs of chromosomes, including one pair that dictates whether a baby will be a boy or a girl. Women ...

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 ...

The embryonic testis makes male hormones which direct the embryo to develop as a boy ... embryo develops as a girl. The 1:1 ratio results from the way the X and Y chromosomes are doled out ...

The baby will be a boy, right? If you don’t see any Y chromosomes, a girl. Similarly, a fetus with Down Syndrome has three copies of chromosome 21, rather than two, but two copies of all of the ...

Many of us learned in high school biology that sex chromosomes determine a baby’s sex, full stop: XX means it’s a girl; XY means it’s a boy. But on occasion, XX and XY don’t tell the whole ...

What are at-home gender test kits? If you're eager to find out whether you're having a baby boy or a girl, you don't have to ...

The Science of Fraternal Twins 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 ...

Klinefelter syndrome is a genetic condition in which a boy is born with an extra X chromosome. Instead of the typical XY chromosomes in men, they have XXY, so this condition is also called XXY ...

Increased risk for autism appears to be linked to the Y chromosome, a Geisinger Health System study has found, offering a new explanation for the greater prevalence of autism in males. The results ...

Olivia, who was born in Huddersfield England, is the only person in the world who has all the three symptoms of Chromosome 6 Deletion ... the little girl had a tyre mark on her chest but the ...