i've been wondering how we came about the XX and XY chromosomes..like after fertilization, where do this sex chromosomes came from?
2007-01-31 02:56:41 · 5 answers · asked by iraperzari 2 in Science & Mathematics ➔ Biology
It happens right at fertilization. The egg is always x and the sperm is either x or y.
2007-01-31 03:01:27 · answer #1 · answered by Gen•X•er (I love zombies!) 6 · 0⤊ 0⤋
Females have two copies of the X chromosome, one from each parent. Males have an X and a Y chromosome, the X chromosome comes from his mother and the Y chromosome from his father. When the chromosomes pair at the time of conception, it depends on chance as to whether the X from the female combines with an X from the male or the Y from the male. In a sense we could say that the male sex chromosomes are the sex detemining ones. If the sperm cell that fuses contains an X chromosome, the offspring is female. If the sperm cell contains a Y chromosome, the offspring is male.
2007-01-31 11:04:47 · answer #2 · answered by docrider28 4 · 0⤊ 0⤋
Our gender is determined from the moment the sperm meets the egg. Your parents each have 23 pairs (23*2=46) of chromosomes. The 23rd pair is the sex chromosomes. In your parents sexual reproduction machinery meiosis occurs and the sperm and eggs (having only 23 chromosomes instead of 46) are produced, during intercourse the an egg and a random sperm join to form a new set of 23 pairs (=46) of chromosomes. Your mom has XX and contributes an X to you. You father has an XY and it is a matter of chance of which sperm has an X and which has a Y.
2007-01-31 11:30:40 · answer #3 · answered by Shanna J 4 · 0⤊ 0⤋
Meiosis (just at fertilization process) results in a random segregation of the genes contributed from each parent. Each parent organism generally has the same genetic make-up, but differs for a fraction of their genes. When gametes first fuse at fertilisation, the chromosomes donated by the parents are combined. But the X and Y chromosomes do not undergo crossover events, so that means that the entire chromosomes from father or mother intervenes. From father X or Y is chosen, from mother any of the two X, from that hazardous choise sex derives.
2007-01-31 11:07:19 · answer #4 · answered by Jano 5 · 0⤊ 0⤋
The gender is determined by the sperm cell that fertalizes the Ova
2007-01-31 11:03:01 · answer #5 · answered by wyzrdofahs 5 · 0⤊ 0⤋