(Downloading may take up to 30 seconds.
If the slide opens in your browser, select File -> Save As to save it.)
Click on image to view larger version.


Figure 4


Fig. 4. A problem with the two factor model. After XCI, XTsix{Delta}CpG:XTsix{Delta}CpG ES cells make three cell populations: one with a single active X (Xa) chromosome and a single inactive X (Xi) chromosome; one with two Xa chromosomes; and one with two Xi chromosomes. (A) Cells with normal XCI result from blocking factor (BF) binding to one X chromosome and the competence factor (C) binding to the other. (B) Cells with two Xa chromosomes and two Xi chromosomes result from BF and C binding to the same X chromosome. However, it is not clear how having both BF and C bound to a single X chromosome results in these two different populations of cells.