Sex Determination

Also called

sex chromosomes · X chromosome · Y chromosome · XX female · XY male · 23 pairs of chromosomes · autosomes · karyotype · egg and sperm · gametes · fertilisation · zygote · girl or boy · 50:50 chance · the father decides · लिंग निर्धारण · गुणसूत्र · युग्मक

Topics

• Human cells carry 23 pairs of chromosomes: 22 pairs of autosomes and one pair of sex chromosomes.
• A woman has two X chromosomes (XX); a man has one X and one much shorter Y (XY).
• Every egg carries one X, because the mother has only X chromosomes to give.
• Half the sperm carry an X and half carry a Y, so the sperm that fertilises the egg decides the sex of the child.
• An X sperm makes an XX zygote, a girl; a Y sperm makes an XY zygote, a boy.
• The chance of a girl or a boy is equal, 50 : 50, at every fertilisation.
• The mother cannot decide the sex of her child; blaming her for a daughter has no scientific basis.
• Not all animals use chromosomes: in some reptiles the temperature of the eggs decides the sex.

About this model

A GLB file of about 250 KB, shown in Lably's 3D viewer and, on a phone, placed in your room with AR. Credit: Model, science and animation: Lably (built procedurally with three.js; no downloaded meshes). | CC BY 4.0. Original geometry and animation made for Lably.

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