Saturday, January 24, 2009
X-Linked and Y-Linked Inheritance
X-Linked and Y-Linked Inheritance
X-linked genes are found on the sex X chromosome. X-linked genes just like autosomal genes have both dominant and recessive types. Recessive X-linked disorders are rarely seen in females and usually only affect males. This is because males inherit their X chromosome and all X-linked genes will be inherited from the maternal side. Fathers only pass on their Y chromosome to their sons, so no X-linked traits will be inherited from father to son. Females express X-linked disorders when they are homozygous for the disorder and become carriers when they are heterozygous. An infamous recessive X-linked disorder is Hemophilia A. Hemophilia is a disorder where blood does not clot properly due to a shortage of clotting factor VIII. This disorder gained recognition as it traveled through royal families, notably the descendent's of Britain's Queen Victoria. X-linked dominant inheritance will show the same phenotype as a heterozygote and homozygote. Just like X-linked inheritance, there will be a lack of male-to-male inheritance, which makes it distinguishable from autosomal traits. One example of a X-linked trait is Coffin-Lowry syndrome, which is caused by a mutation in ribosomal protein gene. This mutation results in skeletal, craniofacial abnormalities, mental retardation, and short stature.
X chromosomes in females undergo a process known as X inactivation. X inactivation is when one of the two X chromosomes in females is almost completely inactivated. It is important that this process occurs otherwise a woman would produce twice the amount of normal X chromosome proteins. The mechanism for X inactivation will occur during the embryonic stage. For people with disorders like trisomy X, where the genotype has three X chromosomes, X-inactivation will inactivate all X chromosomes until there is only one X chromosome active. X inactivation is not only limited to females, males with Klinefelter syndrome, who have an extra X chromosome, will also undergo X inactivation to have only one completely active X chromosome.
Y-linked inheritance occurs when a gene, trait, or disorder is transferred through the Y chromosome. Since Y chromosomes can only be found in males, Y linked traits are only passed on from father to son. The testis determining factor, which is located on the Y chromosome, determines the maleness of individuals. Besides the maleness inherited in the Y-chromosome there are no other found Y-linked characteristics.
...this means to anyones logic, that "somebody" wants, only female
traits to be passed on, and not the "fathers"...!
...i've seen boys that are more of the likes of the Dad than the Mum...!
...is this like the Bible, to protect the female, and guarantee, the females
proliferation...!? ...being men more stronger than females...! ...so that
there are enough females for the guaranteed continuance of humanity...!
...what is the truth...?!
...it could be as i have indicated, the truth has not been told...!
...or it is a well kept "secret"...!
...WHAT DOES IT MEAN, THE "COINCIDENTAL", OR "NICELY
COINCIDENTAL", OR "TOO COINCIDENTAL" issue of the
similarity between the Earth axis inclination of around 23 degrees,
and the 23 chromosomes of sperm or "eggs"/ovules...? ? ?