# DBT JRF 2020 — Question 97

Exam: DBT JRF 2020 · Section: B · Topic: Genetics · Difficulty: Medium

## Question

Which of the following process does NOT contribute to conversion of a proto-oncogene to oncogene?

## Options

- **A.** activating mutation in proto-oncogene
- **B.** de-activating mutation in proto-oncogene
- **C.** increased expression of proto-oncogene
- **D.** de-activating mutation in tumor suppressor

## Answer

Option B

## Explanation

Proto-oncogene → oncogene transformation requires gain-of-function mechanisms: (1) Activating point mutations — e.g. KRAS G12V/D, BRAF V600E; constitutively active; (2) Gene amplification — overexpression; e.g. HER2/ERBB2 amplification in breast cancer; (3) Chromosomal translocation — fusion with a strong promoter or creation of chimeric oncogene (e.g. BCR-ABL in CML, EML4-ALK in NSCLC). A DE-ACTIVATING (loss-of-function) mutation in a PROTO-ONCOGENE would REDUCE or eliminate its activity — making it less oncogenic, not more. (Loss-of-function mutations in TUMOUR SUPPRESSOR genes, e.g. TP53, RB1, drive cancer.) Therefore 'de-activating mutation in proto-oncogene' does NOT convert it to an oncogene.

Source: https://mypyqbuddy.com/questions/which-of-the-following-process-does-not-contribute-6a05a8a02adafec470293279