Head and neck squamous cell carcinoma (HNSCC) affects approximately 890,000 patients worldwide each year, primarily as a result of tobacco and alcohol use or infection with high-risk strains of human papillomavirus (HPV). Despite current therapeutic strategies including surgery, radiation, chemotherapy, immunotherapy, and targeted therapy, the mortality rate remains at approximately 50%. HNSCC tumors exhibit significant genetic heterogeneity, characterized by a high frequency of point mutations and somatic copy number alterations (CNAs). While numerous genomic loci affected by CNAs have been identified, their mechanistic contributions to tumorigenesis remain incompletely understood. Early and frequent genetic alterations in HNSCC include the loss of tumor suppressors within the INK4/ARF locus (9p21.3), particularly CDKN2A, in conjunction with TP53 mutations. The INK4/ARF locus contains several genetic elements, with point mutations predominantly targeting p16. However, about one-third of patient tumors exhibit homozygous deletions of the entire region, representing an additional mode of inactivation. In addition to INK4/ARF loss, two of the most commonly deleted loci in HNSCC involve CSMD1 (8p23.2) and LRP1B (2q22.1). Although these genes have been implicated as tumor suppressors in other cancers, their role in HNSCC is unclear. One of the major challenges in studying large-scale chromosomal deletions has been the difficulty of recreating them in an appropriate model system. Here, I describe two different approaches for generating large deletions (~1.7 kb – 1.2 Mb) in primary human keratinocytes using CRISPR/Cas9 via transfection and electroporation. These approaches enabled creating targeted deletions within CSMD1 and LRP1B, as well as performing a functional dissection of the INK4/ARF locus to evaluate the roles of its genetic elements and various gene inactivation mechanisms. My results indicated that CSMD1 and LRP1B deletions were passenger events in the contexts examined, with no clear evidence supporting a pathogenic role in HNSCC tumorigenesis. I propose that alterations in these genes are more likely to represent common fragile sites. Furthermore, analysis of the INK4/ARF locus indicated that p16 was the essential tumor suppressor within this region, with point mutations and deletions exhibiting comparable biological outcomes. Additionally, there was no evidence that other genetic elements within the locus such as the regulatory domain (RD) element, p15, or p14 contribute to HNSCC tumorigenesis. These results have implications for future disease modeling as well as targeting the most critical pathways for therapeutic approaches.