Question

______ ______ implies that cancerous cells are all derived from a single cancerous cell, because all the cancerous cells have the same inactivated X chromosome.

Answer 1

The question pertains to the clonal origin of cancer, supported by the occurrence of X inactivation in female mammals, resulting in a Barr body in each cell.

Step-by-step explanation:

The concept described in the student's question is called X inactivation, which is a process occurring during the early developmental stages in female mammals. One X chromosome in each cell is inactivated, and this inactivation is random but permanent for all daughter cells derived from that initial cell. This inactivation leads to the formation of a structure called a Barr body. The presence of identical inactive X chromosomes among all cancerous cells supports the idea that these cells originated from a single cancerous cell – a concept known as the clonal origin of cancer.