Knudson’s two stage hypothesis is for-
**Core Concept**
Knudson's two-stage hypothesis proposes that carcinogenesis involves two distinct stages: initiation and promotion. This theory applies to retinoblastoma, a type of cancer that affects the retina of the eye. It suggests that a single mutation in a tumor suppressor gene is sufficient to initiate cancer, while subsequent mutations are required for tumor progression.
**Why the Correct Answer is Right**
Knudson's hypothesis was specifically developed to explain the high incidence of retinoblastoma in individuals with a family history of the disease. The theory states that a germline mutation in the RB1 gene, which encodes the retinoblastoma protein, is inherited from one parent and serves as the initiating event. Subsequent somatic mutations in the remaining RB1 allele lead to the development of retinoblastoma. This two-stage model has been widely applied to other types of cancer, including osteosarcoma and small cell lung cancer.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because Knudson's hypothesis is specific to retinoblastoma and does not apply to all types of cancer.
**Option B:** This option is incorrect because the two-stage hypothesis is not related to the concept of carcinogenesis in the context of environmental factors.
**Option C:** This option is incorrect because Knudson's hypothesis is not directly related to the role of oncogenes in cancer development.
**Clinical Pearl / High-Yield Fact**
Knudson's two-stage hypothesis highlights the importance of tumor suppressor genes in preventing cancer and the concept of genetic predisposition to cancer.
**Correct Answer: D. Retinoblastoma**