Correct option is B
Correct Evaluation:
Statement A:"Auxin can be used as a negative selection marker in plant transgenesis as it can be lethal to germinating seedlings at higher concentrations."
Correct: Auxin, at higher concentrations, can inhibit the growth of germinating seedlings and is indeed used as a negative selection marker.
Statement B:"Agrobacterium inserts T-DNA at random locations in the plant genome and thus, it cannot be targeted to a desired location."
Correct: T-DNA integrates randomly into the nuclear genome of the host plant. The insertion does not require sequence homology, and therefore it cannot be directed to a specific genomic site under normal transformation conditions.
Studies show that T-DNA favors transcriptionally active (euchromatic) regions, but this is not precise targeting.The randomness of insertion can cause position effects, gene disruptions, or variable expression levels.
Statement C:"The antibiotic kanamycin interferes with the cytoplasmic ribosomal protein synthesis machinery, thereby acting as a positive selection marker."
Incorrect: Kanamycin is a negative selection marker because it inhibits protein synthesis by binding to the ribosomes and killing the plant cells that do not carry the kanamycin resistance gene. This helps to select for the transformed cells.
Statement D:"Gene transfer by biolistic/particle gun bombardment usually results in lower transgene copy number and less DNA rearrangement than Agrobacterium-mediated transformation."
Incorrect: Biolistic transformation usually leads to higher transgene copy numbers and more DNA rearrangements compared to Agrobacterium-mediated transformation, which generally results in fewer copies and less disruption of the DNA.
