Transgenic models: These models have additional genes inserted into their genome. For example, the Myc transgenic mouse model is widely used to study lymphomas. Knockout models: Specific genes are inactivated in these models. The p53 knockout mouse is used to study the role of p53 in various cancers. Conditional models: These models allow gene activation or inactivation at specific times or in specific tissues, providing insights into the temporal and spatial roles of genes in cancer.