正常人类的细胞中有44条常染色体,还有一对性染色体。女性的一对性染色体形态和长度都一样,称X染色体,用“XX”表示;男性的一对性染色体中,有一条与女性相同,另一条较小、较短,称Y染色体,用“XY”表示。当带有X染色体的精子与卵子结合时,生下的孩子就是女的;当带有Y染色体的精子与卵子结合时,生下孩子就 Normal human cells have 44 autosomes, there is a pair of sex chromosomes. A female sex chromosome shape and length are the same, called the X chromosome, with “XX ” said; male sex chromosomes, one with the same female, another smaller, shorter, said Y chromosome, With “XY ” said. When a sperm with an X chromosome binds to an egg, the child born is a female; when a sperm with a Y chromosome binds to an egg, it gives birth to a child