Women (and all female mammals) have one active X chromosome per cell instead of two. What causes this?
A) modification of the XIST gene so that it is active only on one X chromosome, which then becomes inactive
B) activation of the Barr gene on one of the two X chromosomes that then inactivates
C) crossover between the XIST gene on one X chromosome and a related gene on an autosome
D) inactivation of the XIST gene on the X chromosome derived from the male parent
E) the removal of methyl (CH3) groups from the X chromosome that will remain active
Examples of cell-to-cell communication based on the distance between cells
A missense mutation that causes red blood cells to sickle in sickle-cell anemia.
E. coli bacteria cell
A juvenile and a female torrent duck on the Urubamba River, Peru
Surface molecules involved in the interaction between an antigen-presenting cell and a CD4+ T cell.
Reproductive Cell Division: Meiosis II