Molecular Biology
Core concepts
Master the central dogma: replication, transcription, translation, and post-translational modification. Know DNA repair mechanisms, oncogene versus tumor suppressor logic (activation vs loss of function), and the two-hit hypothesis. Understand PCR, sequencing, and their clinical roles in urologic oncology (e.g., detecting mutations, liquid biopsy concepts). Familiarize yourself with epigenetic regulation and the cell cycle checkpoints.
Traps
Questions often test whether a mutation is gain-of-function (oncogene) or loss-of-function (tumor suppressor), and whether one or two hits are needed. Distinguish germline from somatic mutations. Another trap: confusing transcription (DNA→RNA) with translation (RNA→protein) locations and enzymes. Watch for questions about which repair pathway fixes which lesion (mismatch repair vs nucleotide excision repair vs double-strand break repair).
Rule of thumb
Oncogenes need one activating hit; tumor suppressors typically require biallelic loss (two-hit). For DNA lesions: mismatch repair for replication errors, nucleotide excision repair for bulky adducts/UV damage, homologous recombination for double-strand breaks.
Worked example
A tumor shows loss of both alleles of a tumor suppressor gene. This fits the two-hit hypothesis: a germline hit plus a somatic hit, or two somatic hits, leading to absent protein function and uncontrolled proliferation.