Final answer:
Li-Fraumeni syndrome is diagnosed by genetic testing for a mutation in the TP53 gene, which causes a dysfunctional p53 protein that fails to regulate the cell cycle or trigger apoptosis, leading to increased cancer risk.
Step-by-step explanation:
Mutations in the DNA repair checkpoint gene TP53 underlie Li-Fraumeni syndrome (LFS), which can be diagnosed based on genetic testing that identifies the mutation in the TP53 gene.
Li-Fraumeni syndrome is a hereditary cancer syndrome that significantly increases the risk of developing various types of cancer over an individual's lifetime. In LFS, mutated p53 protein fails to stop cell division even if the cell's DNA is damaged, leading to an increased possibility of developing cancer.
The presence of a mutated TP53 gene results in the synthesis of an abnormal p53 protein, which is intended to monitor DNA and coordinate DNA repair or initiate apoptosis (programmed cell death) in the event that the DNA damage is irreparable. However, due to the mutation, p53 loses its function, and as a result, cells accumulate genetic mutations and increase the risk of cancer.