There is a genetic disorder known as turners syndrome. I want to ask, why are only women affected and not men?

Question

If you are a science student you may know that!
just analyse chromosomal basis of inheritance! you may get answer to my question!

Answer 1

Sometimes during maturing of the egg cell, the two XX chromosomes do not separate (nondisjunction) resulting in one egg cell having both XX chromosomes and the other having no X chromosome ("0").
A sperm cell will carry either an X or a Y chromosome.
These are the possibilities during fertilization:

Sperm X + Egg "0" (no X) = X0 Female, Turner's syndrome, has 45 body chromosomes instead of normal 46.

Sperm X + Egg XX = XXX "superfemale" , 47 body chromosomes

Sperm Y + egg XX = XXY Kleinfelter's syndrome (I think)
female (?) 47 body chromo.

Sperm Y + egg "0" = Y0 LETHAL (no development)

Answer 2

Turner syndrome is characterized by the presence of a single complete functioning sex-determining chromosome, the X chromosome, instead of two, either XX or XY. This chromosomal arrangement normally occurs in four ways.

* During meiosis in either parent, a nondisjunction event can occur that leaves the gamete, either oocyte or spermatocyte with neither X nor Y chromosome. When this gamete combines with a gamete from the other parent (with a normal X chromosome), the embryo lacks the normal two chromosomes. Normally, humans have 46 chromosomes, so this leaves the embryo with 45 chromosomes and a single X chromosome, denoted 45,X (or, sometimes 45,XO, where the "O" is used as a placeholder). This is found in 50% of individuals with Turner syndrome.

* During development leading up to gametogenesis, an X chromosome loses a portion of the smaller arm, with the end of the long arm wrapping around — creating a ring-like structure. The chromosome is missing the short arm of the X chromosome. When combined with a normal X chromosome in an embryo, the individual has just a single copy of the information on the short arm of the X chromosome. This is denoted as 46, XrXp-, where rXp- means a ring chromosome missing the small (p) arm of the chromosome. Other chromosomal variants have two long arms of the X chromosomes attached, and are called isochromosomes. Variants of chromosomal structure occur in 30% of individuals with Turner syndrome.

* During an early cell division of the zygote, a nondisjunction event occurs and creates a cell line that is missing the second X chromosome. In this case, individuals most likely have a mixture of 46,XX cells and 45,X cells. This is called mosaicism. The exact mixture of those two cell types depends on when the nondisjunction occurred. It is possible for a very early nondisjunction from a 46,XY zygote to be completely 45,X (and are indistinguishable from the first classification). If the nondisjunction occurs later, a 45,X/46,XY individual will develop as a male, without Turner syndrome. Mosaicism is found in about 20% of individuals with Turner syndrome.

* Very rarely, the embryo has a normal X chromosome and a portion of the Y chromosome. In these cases, the Y chromosome does not have a functional SRY (and so develops as a female), the diagnosis is gonadal dysgenesis (see OMIM entry for SRY). It is possible that some Turner syndrome diagnosis is due to gonadal dysgenesis, particularly when it is caused by a large deletion of the Y chromosome.

There is no equivalent syndrome which results in a Y chromosome with no X, as such a condition is incompatible with life. Because an embryo with Turner syndrome doesn't have a Y chromosome (or, doesn't have a functional SRY on the Y chromosome), it will move along the path to female development.

Risk factors for Turner syndrome are not well known. Nondisjunctions increase with maternal age, such as for Down syndrome, but that effect is not clear for Turner syndrome.

Note: Men have to have a Y chromosome to show masculine features whereas women are women even if they only have one X chromosome! :))

Answer 3

Normally, each cell in the body contains 23 pairs of chromosomes. There is a pair of chromosomes known as the sex chromosomes that are composed of two X's in most females and a single X plus a Y chromosome in most males. This means most women have a chromosome makeup known as 46,XX and most men have a chromosome makeup known as 46,XY. In most cases of Turner syndrome, a single X chromosome is present, resulting in a 45,X chromosome makeup.

Individuals with Turner syndrome are female in gender although they are infertile because of incomplete development of the ovaries. They are not male because they lack the Y chromosome which contains important genetic factors that allow for development of male genitalia.

Answer 4

Turner's syndrome is also known as XO syndrome. Normally, people are either XX (women) or XY (men). Those with Turner's syndrome only have the one X.

It is this X which means patients with Turner's syndrome will always be girls. To display male characteristics, you MUST have a Y chormosome. Therfore, is you only have Xs (be it 1, 2 or 3) you will automatically be a girl.

XO is a 'syndrome' because humans are meant to have 2 copies of every chromosome. X and Y are the sex chromosomes, and again, you're meant to have 2 - XX or XY. As Tuner Syndrome patients only have one, they will display abnormailities resulting from the missing chromosome.

Answer 5

Turner's causes a lack of the Y chromosome. An individual who doesn't have a Y chromosome is always a female.