# DBT JRF 2020 — Question 9

Exam: DBT JRF 2020 · Section: B · Topic: Biotechnology · Difficulty: Hard

## Question

During genome engineering process, the role of Flippase enzyme in the next round of modification in the target gene is to

## Options

- **A.** remove the antibiotic cassette
- **B.** add frt sequence
- **C.** remove frt sequence
- **D.** add the antibiotic cassette

## Answer

Option A

## Explanation

Flippase recombinase (FLP recombinase from Saccharomyces cerevisiae 2μ plasmid) catalyses site-specific recombination between two FRT (Flippase Recognition Target) sequences. In the Cre-lox/FLP-FRT system used for genome engineering: Step 1 — An antibiotic resistance cassette (for selection) flanked by two FRT sites is knocked into the target gene. Step 2 — After selection confirms successful targeting, FLP recombinase is expressed, catalysing recombination between the two FRT sites — excising and REMOVING the antibiotic cassette. This leaves a single FRT 'scar' and a clean locus ready for the next round of modification. Without FLP removal of the antibiotic marker, the same marker cannot be used again in subsequent modifications.

Source: https://mypyqbuddy.com/questions/during-genome-engineering-process-the-role-of-flippase-6a05a8a02adafec470293221