Chromosomes

[daniel.kurz]

If you have XXY or more than 2 Xs and a Y you have something callled Nondisjunction or trisomy. This generally means that you develop down syndrome during development. You can't have a YY because YY only codes for a certain number of chromsomes. You must have at least one X chromosome for the coding of tissues to be developed. The X chromsome codes for all the needed proteins and cells needed to develop. Without those codes the embryo will not develop.

[LilKim]

if you have XXY you have kleinfelters.... (and if you have XXXY you still have kleinfelters)

down syndrome is caused by trisomy 21 (it has nothing to do with the sex chromosomes)

Both klienfelters and trisomy 21 are a consequence of non-disjunction.

There are many examples of males born with XYY and XYYY... in the past, they even tried to link this karyotype with aggresiveness, violent behavior and other social problems (.. scientists tried to prove that a significanltly greater population of male prison inmates had this these karytypes .... however, no one has ever conclusively shown it to be true)

Thus XYY doesn't code for "a certain number of chromosomes" .. it's simply just another sex chromosome complement.

As far as an X chromosome.. yes, 1 X chromosome is necessary for survival... however all of the other autosomal chromosomes code for other genes necessary for life.

(other genes necessary for life and normalcy exist at other genomic locations besides the X chromosome ... that's why monosomy of any autosomal chromosome is a lethal condition)

hope i've clarified some stuff for ya
- kim

[daniel.kurz]

Well the cases of XXXY or more X chromosomes are extremely rare. That is why you will rarely find a calico male cat. The chromosomes for calico spots is only found in that of women because it is controlled by the X chromosomes. This is caused by selective chromsomes and they can turn on and off. You must have two XXs so a male calico is automatically a case of trisomy.

[oana_t]

there are more cases that can make determine death.for example there are some genes called the lethal genes which provoke the death of the death of the egg in homozygote stadium.also an egg can't survive if it doesn't have the x chromosone.there are some syndroms as well for example :klinefelter when the chromosomes are XXY and Turner when the individual has no Y gene.

[student12]

Just curiosity...how do you get a Y0?

[LilKim]

So i'll start of with nomenclature. In the past, the convention for writing turner syndrom was '45,XO' however more recently the karyotype was modified to: 45,X ... simply because there is no such thing as an 'O' chromosome.

An X chromosome is necessary for life... so no human being can be born without an X chromosome.. thus a : 45,Y would not produce a viable child... and the mother would probably abort the pregnancy very early

- KIM