Sex Determination in humans

What is Sex determination? How can we determine the sex in humans?

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Sex determination in humans:

Sex determination in humans is typical of the process in other mammalian species, and although the sex chromosomes are XX and XY, the genetic basis of sex determination differs markedly from that described for Drosophila.
Our understanding of this subject comes from the study of sex chromosome aneuploids.
Aneuploidy of sex chromosomes arises more frequently than for autosomes because very few genes are present on the Y chromosome and due to the phenomenon of X chromosome inactivation , only one X chromosome is expressed in any cell.
Hence alterations to the numbers of sex chromosomes have less effect on viability than do changes to the autosomes.
The sex of several sex chromosome aneuploids is given in the below table.
Not all of these sex chromosome configurations result in fertile individuals and individuals with the more extreme deviations from normal suffer severe mental retardation.
From these examples it is clear that at the chromosomal level the presence of a Y chromosome is the factor which determines maleness in humans.
During early embryonic development the presence of a Y chromosome causes the is differentiated gonad to grow more rapidly and subsequently to develop into testes.
In birds, where the ZZ-ZW sex determining system is essentially the reverse of the XX-XY, the presence of a W chromosome induces the development of ovaries from undifferentiated gonads.
A specific gene, SRY, mapping to the Y chromosome in both humans and mice has been isolated that is responsible for the switch from female to male development in embryos.

Sex chromosomes	Chromosome number	Sex
X	45	Female
XXX	47	Female
XXXX	48	Female
XXXXX	49	Female
XYY	47	Male
XXY	47	Male
XXXY	48	Male

Sex Determination:

The sex-determination system is a biological system which determines the development of sexual characteristics in an organism.

Suhasini Buddi answered 1 year ago

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