Question

APC is a tumor suppressor and acts in the Wnt signaling pathway to prevent the

TCF complex from turning on Wnt-responsive genes. Mice that lack the gene
encoding TCF4 do not have the ability to maintain the pool of proliferating gut
stem cells needed to renew the gut lining. What do you predict will happen in
mice that lack the APC gene?
(a) Mice lacking the APC gene will be like the mice lacking TCF4 and not be
able to renew the gut lining.
(b) Mice lacking the APC gene will have inappropriate proliferation of gut
stem cells.
(c) Mice lacking the APC gene will have a hyperactive Wnt receptor even
though there is no Wnt signal.
(d) Mice lacking the APC gene will be like normal healthy mice, since APC is
a tumor suppressor and thus not needed unless there is a tumor present.

Answer 1

The absence of the APC gene in mice leads to inappropriate proliferation of gut stem cells due to the unchecked Wnt signaling pathway, potentially leading to tumor development.

Step-by-step explanation:

In mice lacking the APC gene, which is a critical tumor suppressor gene in the Wnt signaling pathway, one would predict that there will be inappropriate proliferation of gut stem cells. This is because the APC gene's function in normal cells acts as a 'brake pedal,' inhibiting cell division and proliferation by degrading the beta-catenin protein, which would otherwise go on to activate TCF and promote expression of Wnt-responsive genes that lead to cell proliferation. In the absence of APC, the Wnt signaling is left unchecked, resulting in constant activation of TCF and persistent cell division, even in the absence of Wnt signals, potentially leading to tumor development in the gut lining.