Correct option is B
Explanation-
Statement A - Evidence derived by chromosome conformation capture (3C) suggests that each chromosome comprises a series of topologically associated domains (TADs).
Correct
3C techniques (including Hi-C, 4C, 5C) revealed that chromosomes are organized into TADs—regions where DNA sequences preferentially interact with each other. This compartmentalization plays a crucial role in gene regulation.
Statement B - Insulators typically mark the boundaries of topologically associated domains, preventing the genes within a domain from being influenced by the regulatory modules of an adjacent domain.
Correct
CTCF is a common insulator-binding protein that often marks TAD boundaries. Insulators block enhancer–promoter interactions across domains, maintaining proper gene expression within a TAD.
Statement C - Presence of insulators does not overcome the positional effect after integration of a transgene into the genome.
Incorrect
One of the classic roles of insulators is to mitigate the positional effect, i.e., shielding transgenes from neighboring enhancers/silencers.
So this statement contradicts known experimental evidence.
Statement D - Insulators can provide barrier against the spread of heterochromatin.
Correct
Insulators also act as barrier elements, blocking the spread of heterochromatin into euchromatic (active) regions. It prevents gene silencing caused by heterochromatin invasion.
Statement E- Insulator sequences are absent in the Drosophila genome, which suggests their essentiality in achieving highest degree of gene regulation in humans.
Incorrect
Drosophila has insulators like gypsy, scs, and scs′, which have been well-studied. The statement is factually wrong: insulators are present in Drosophila, and humans and flies both use them for regulation, though with some differences.
Since statement A, B and D are correct so the correct answer is option b -A, B and D.
