What likely outcome is expected in mice that lack the Apc gene?

Mice that lack the Apc gene are expected to experience inappropriate proliferation of gut stem cells. The Apc gene is a crucial tumor suppressor gene that plays a significant role in regulating cell growth and maintaining cellular homeostasis in the gut epithelium. In the presence of the Apc protein, the Wnt signaling pathway is kept in check, preventing excessive cell division and promoting normal differentiation of gut epithelial cells.

When the Apc gene is absent, Wnt signaling becomes dysregulated. This uncontrolled signaling leads to the activation of genes that promote cell proliferation while inhibiting differentiation, resulting in an abnormal increase in the number of stem cells and progenitor cells in the gut lining. This inappropriate proliferation can lead to the development of gastrointestinal tumors, particularly adenomas, which are precursors to colorectal cancer.

The other outcomes provided do not accurately reflect the consequences of Apc gene loss. For example, while hyperactive Wnt signaling does occur due to the absence of Apc, the primary observable consequence in the gut is the increased proliferation of gut stem cells. Therefore, the expected outcome of inappropriate proliferation aligns with the known biological roles of the Apc gene in tumor suppression and cell cycle regulation.