Gene dosage effects of extra copies of SHOX may be a cause of the increased stature seen in other sex chromosome aneuploidy conditions such as 47, XXX, 47, XYY, 47, XXY, 48, XXYY, etc.
22.
Assuming that no regulatory feedback loops exist that automatically down-regulate gene expression, the amount of gene product ( or gene dosage ) will increase with each additional gene copy, until some upper limit is reached or sufficient gene product is available.
23.
The mechanisms leading to novel variation in newly formed allopolyploids may include gene dosage effects ( resulting from more numerous copies of genome content ), the reunion of divergent gene regulatory hierarchies, chromosomal rearrangements, and epigenetic remodeling, all of which affect gene content and / or expression levels.
24.
In eukaryotes, most genes found in the cell are expressed as autosomal genes ( see autosome ) and are found in two copies, alterations to this two-copy gene dosage is significantly associated with quantitative or qualitative phenotype traits and is linked to many genetic health problems such as those associated with spinal muscular atrophy and Down syndrome.
25.
The SHOX gene in the PAR1 region is the gene most commonly associated with and well understood with regards to disorders in humans, but all pseudoautosomal genes escape X-inactivation and are therefore candidates for having gene dosage effects in sex chromosome aneuploidy conditions ( 45, X, 47, XXX, 47, XXY, 47, XYY, etc . ).
