​A transgenic line was developed in mustard. The T₀ transgenic line was selfed, and the insertion of the transgene was analyzed in the parental (P) and progeny lines (1 to 5). The T-DNA region (between left border (LB) and right border (RB)) used for transformation is outlined in Figure A.

The pattern following Southern hybridization using probes A and B is represented in Figure B. The genomic DNA was digested with EcoRI (E). The thickness of the band indicates the intensity of hybridization

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Statements based on the observation:

A. The developed transgenic line has a single copy of T-DNA.
B. The absence of a band in progeny 4 is due to incomplete transfer of the T-DNA during transformation.
C. Progeny 2 is homozygous at the site of insertion.
D. All selfed progeny of line 5 is expected to show hybridization with both probes A and B.

Which one of the following options has all of the correct statements?

Correct option is D

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Explanation:

1. Statement A (Correct)
• The hybridization pattern shows a single band for each probe, indicating that a single copy of T-DNA has been inserted into the genome.
2. Statement B ( Incorrect)
• The absence of a band in progeny 4 suggests segregation of the transgene, not incomplete transformation. Since the parental plant is heterozygous, there is a chance that some progeny (like progeny 4) do not inherit the transgene at all.
3. Statement C (Correct)
• Progeny 2 shows a single band of uniform intensity, indicating that both alleles have the transgene inserted at the same site. This suggests that progeny 2 is homozygous for the transgene.
4. Statement D ( Correct)
• Since line 5 has hybridization signals with both Probe A and Probe B, all selfed progeny from line 5 will inherit these sequences, leading to continued hybridization with both probes.