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#loxP

2 public questions tagged with this topic.

Gene Tar getting

What is the result of placing loxP sites in opposite orientation?

Outcome of Cre-loxP recombination depends strictly on relative orientation and location of loxP sites. When two loxP sites in same DNA molecule are oriented in same direction, Cre excises the intervening segment as a circular product leaving one loxP scar. When loxP sites are in opposite orientation, Cre does not delete but reverses the strand polarity between them, inverting the intervening sequence. This inversion property underlies Cre-FLEX and DIO systems where gene orientation flips reversibly, enabling conditional activation, silencing and lineage tracing applications in neuroscience.

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

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Gene Tar getting

The Cre recombinase enzyme recognizes which DNA element?

Cre is a 38 kDa tyrosine recombinase encoded by bacteriophage P1 that catalyzes site-specific recombination without cofactors. Its target is loxP, a 34 base pair sequence containing an asymmetric 8 base pair core spacer flanked by two 13 base pair inverted repeats where Cre binds as dimer. Recombination between two loxP sites excises or inverts intervening DNA depending on orientation. Specificity for loxP distinguishes Cre from Flp which recognizes FRT, making Cre-loxP a powerful conditional genome manipulation tool in mammals.

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

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