Final answer:
The two problems with leptin in genetically engineered mice are leptin resistance and decreased sensitivity to leptin.
Step-by-step explanation:
Leptin resistance refers to a condition where there is a decreased sensitivity to leptin, resulting in an inability to detect satiety despite high-fat reserves. This causes the mice to never feel satiated and to overeat, leading to weight gain.
Decreased sensitivity to leptin means that the mice are less responsive to the hormone leptin, which normally regulates appetite by signaling fullness. This lack of sensitivity to leptin leads to a disruption in the normal regulation of appetite and can contribute to obesity. Therefore the two problems with leptin in genetically engineered mice are leptin resistance and a decreased sensitivity to leptin, these problems result in the mice never feeling satiated and overeating, leading to weight gain.