6. During an experiment, an Investigator found that the cell line used are RecA -/-. What could be the probable finding which led him to such observation?
(1) Low of recombination.
(2) Showing aberrant cell morphology.
(3) Cells developed phagocytic properly.
(4) Cells were aggregating.
RecA-/- cell lines exhibit low levels of homologous recombination due to the absence of the RecA protein, which is essential for DNA strand exchange and repair in bacteria. This deficiency directly impairs genetic recombination processes observed during experiments. The correct answer is option (1) Low of recombination.
Option Analysis
Option (1) Low of recombination
RecA catalyzes homologous recombination by forming nucleoprotein filaments on single-stranded DNA, enabling strand invasion and pairing. In RecA-/- cells, recombination frequency drops dramatically, often by 50- to 100,000-fold, as seen in bacterial mutants where plasmid or chromosomal exchanges fail. This matches the probable experimental finding, as investigators routinely test recombination proficiency in such cell lines.
Option (2) Showing aberrant cell morphology
RecA mutants in bacteria like Leptospira biflexa or E. coli display elongated cells or condensed nucleoids due to unrepaired DNA damage affecting division and chromosome segregation. However, these morphological changes are secondary to DNA repair defects, not the primary diagnostic for RecA-/- identification in recombination-focused experiments.
Option (3) Cells developed phagocytic property
Phagocytosis involves scavenger receptors or complement pathways in immune cells like macrophages, unrelated to bacterial RecA function. No evidence links RecA deficiency to gaining phagocytic traits; bacterial cells lack such properties.
Option (4) Cells were aggregating
RecA influences DNA metabolism but not cell aggregation, which relates to motility factors like flagella or adhesion proteins. Overexpression of RecA may affect swarming, but knockout does not cause aggregation.
