how sex is determined?

Answer 1

By the male. The female has two "X" chromosomes; and the male, an "X" and a "Y".

If the egg (which always carries one "X" chromosome from the mother) is fertilized by a male sperm carrying the "X" chromosome, the child becomes a female; and if the sperm is carrying the "Y," the child is male.

Answer 2

In mammals, by the male gamete (sperm), which either has an "X" chromosome or a "Y" chromosome. The Y chromosome has the effect of switching on several genes on the X chromosome, which sets the zygote (fertilised egg) on the path to being male. If this path isn't switched on, then it becomes female. Therefore in mammals, the presence of a Y chromosome means "male", and the absence of it mean "female", even though the Y has only 50 genes compared to thousands on the X.

Its the opposite way round in birds, which have Z and W chromosomes and the female has the deciding gamete (they look the same as X and Y, but two different letters are used to avoid confusion), and some reptiles/amphibians/insects use temperature to determine the sex of the offspring (ie above a certain temperature the offspring is male, below the temperature the offspring is female, or vice versa)

Answer 3

There are several possible answers.

In mammals, it is done by the presence of a X or a Y chromosome in the spermatozoa that fertilize the egg.

In birds, males are ZZ and females are ZW, so the female is the one that determines the sex of the hatchling, not the male.

For some reptile, the temperature of the incubating eggs determines the sex of the hatchling (cooler will produce more females, warmer more males).

In some fish, gender can be a function of age (born as a female, and becoming male when getting older, or vice-versa) or position in a hierarchy (all fish are female except one, when that one dies or goes away, then one female becomes the male).

It is pretty strange when you consider all the possibilities...

Answer 4

Sex is determined generally by ultrasound imaging of the
genitalia of the fetus. Alternatively, it is done by a procedure called Amniocentensis, in which foetal cells are obtained by injecting a needle into the womb through the stomach skin (not from vaginal opening). The foetal cells are then used to prepare chromosomal spreads. If there are two X chromosomes, then it's a girl and if there are two Y chromosomes, then it's a boy. It's as simple as that.

Answer 5

In human beings there are 21 autosomes and 2 sex chromosomes, male sex chromosome is represented as (XY) and female sex chromosome is represented as (XX). So the outlook of human chromosome goes like....21+XX OR 21+XY.

The process of union between haploid male gamete(n) and haploid female gamete(n),which gives rise to a diploid gamete(2n) is known as ferlilization.It is due to this fertilization, that after a time span of nine months the foetus is born.Though we can know the sex of the child by sonography before he or she is born.

Foetus can be said a male or a female by there chromosomes....which is Male (XY) and Females (XX).

Answer 6

Mum = XX Dad = XY chromosomes. 50/50 chance of either gene to make a sperm or egg. 50/50 chance of baby having a Y chromosome. Y makes the testes which produces testosterone to make a male.

Answer 7

50% of the male sperms have Y chromosome & other 50% has the X chromosome.Female ova has only the X chromosome.
When a sperm with X chromosome fertilizes an ova, a female zygote is formed but when a sperm with Y chromosome fertilizes an ova,a male zygote is formed.

Answer 8

A sex-determination system is a biological system that determines the development of sexual characteristics in an organism. Most sexual organisms have two sexes. In many cases, sex determination is genetic: males and females have different alleles or even different genes that specify their sexual morphology. In animals, this is often accompanied by chromosomal differences. In other cases, sex is determined by environmental variables (such as temperature) or social variables (the size of an organism relative to other members of its population). The details of some sex-determination systems are not yet fully understood.

Chromosomal determination
XX/XY sex chromosomes
The XX/XY sex-determination system is one of the most familiar sex-determination systems and is found in human beings and most other mammals. In the XY sex-determination system, females have two of the same kind of sex chromosome (XX), while males have two distinct sex chromosomes (XY). Some species (including humans) have a gene SRY on the Y chromosome that determines maleness; others (such as the fruit fly) use the presence of two X chromosomes to determine femaleness.

XX/X0 sex determination
In this variant of the XY system, females have two copies of the sex chromosome (XX) but males have only one (X0). The 0 denotes the absence of a second sex chromosome. This system is observed in a number of insects, including the grasshoppers and crickets of order Orthoptera and in cockroaches (order Blattodea).

The nematode C. elegans is male with one sex chromosome (X0); with a pair of chromosomes (XX) it is a hermaphrodite.

ZW sex chromosomes
The ZW sex-determination system is found in birds and some insects and other organisms. The ZW sex-determination system is reversed compared to the XY system: females have two different kinds of chromosomes (ZW), and males have two of the same kind of chromosomes (ZZ).

It is unknown whether the presence of the W chromosome induces female features or the duplication of the Z chromosome induces male ones; unlike mammals, no birds with a double W chromosome (ZWW) or a single Z (Z0) have been discovered. Probably that either condition causes embryonic death, and both chromosomes are responsible for gender selection.

In Lepidoptera, examples of Z0, ZZW and ZZWW females can be found. This suggests that the W chromosome is essential in female determination in some species (ZZW), but not in others (Z0). In Bombyx mori (the commercial silkworm), the W chromosome carries the female-determining genes.

Chromosomes in the ZW region in birds are autosomal in mammals, and vice-versa; therefore, it is theorized that the ZW and XY couples come from different chromosomes of the common ancestor. A paper published in 2004 (Frank Grützner et al, Nature; DOI:10.1038/nature03021 ) suggests that the two systems may be related. According to the paper, platypuses have a ten-chromosome–based system, where the chromosomes form a multivalent chain in male meiosis, segregating into XXXXX-sperm and YYYYY-sperm, with XY-equivalent chromosomes at one end of this chain and the ZW-equivalent chromosomes at the other end.

Haplodiploidy
Haplodiploidy is found in insects belonging to Hymenoptera, such as ants and bees. Haploid individuals are male. Diploid individuals are generally female but may be sterile males. Thus, if a queen bee mates with one drone, her daughters share ¾ of their genes with each other, not ½ as in the XY and ZW systems. This is believed to be significant for the development of eusociality, as it increases the significance of kin selection.

Non-genetic sex-determination systems
Many other exotic sex-determination systems exist. In some species of reptiles, including alligators, sex is determined by the temperature at which the egg is incubated. Other species, such as some snails, practice sex change: adults start out male, then become female. In tropical clown fish, the dominant individual in a group becomes female while the other ones are male.

Some species have no sex-determination system. Earthworms and some snails are hermaphrodites; a few species of lizard, fish, and insect are all female and reproduce by parthenogenesis.

In some arthropods, sex is determined by infection. Bacteria of the genus Wolbachia alter their sexuality; some species consist entirely of ZZ individuals, with sex determined by the presence of Wolbachia.

Other unusual systems [this section still being researched]:
* Swordtail fish?
* The Chironomus midge species
* etc

You could get more information at the link below..

Answer 9

by either the X or Y chromosomes. with a female, the xchromosome given by the mother is paired with the Xchromosome given by the father. with a male, the xchromosome from the mother is paired with the ychromosome of the father.

Answer 10

When the baby is growing inside his genes are going to deside its gender.
Then at the 23 pair of genes if one gene is"x" and another one is "y" then the baby becomes male & if both are "x" then baby becomes female.