Cancer genetics seeks to understand the genetic basis of tumor development through population, cytogenetic, and molecular approaches. It examines inherited mutational occurrences, chromosome abnormalities, and gene-level modifications that are accountable for oncogenesis. Proto-oncogenes, tumor suppressor genes, and DNA repair genes are some of the main molecular elements. Cancer has come to be realized as a genetic disorder by historical events, starting from Hippocrates up to Theodor Boveri. Recent advances single-cell biology, CRISPR, and high-throughput sequencing have transformed diagnostics, prognostics, and individualized treatments. There are difficulties still, though, such as genomic heterogeneity, non-coding mutations, and ethics. The integration of genomic data into clinical management ushers in a new era for precision oncology. New technologies including single-cell biology, CRISPR-Cas9 genome editing, and high-throughput sequencing are changing cancer diagnosis, prognosis, and finding targeted therapeutic methods in cancer. All these developments notwithstanding, there are still challenges such as intratumoral heterogeneity, non-coding mutations, and use of genomic data ethics. Incorporation of large-scale genomic profiling in clinical oncology is a paradigm-shift period for precision oncology with improved and more personalized treatment of cancer patients.