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#double digestion

3 public questions tagged with this topic.

Restriction Digestion & Mapping

Double digestion refers to:

Double digestion involves incubating DNA with two different restriction endonucleases either simultaneously in a compatible buffer or sequentially. The goal is to generate overlapping cleavage maps and assess relative positions of two distinct recognition sequences. Single enzyme digestion provides limited information. Exonuclease digestion degrades from termini rather than cutting internally at specific motifs. PCR-based methods are amplification techniques. Co-digestion with two enzymes typically yields smaller fragments and helps confirm insert orientation, construct verification, and detailed physical maps for cloning strategies.

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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Restriction Digestion & Mapping

Double digestion gives 1.9 kb and 2.9 kb fragments. Total size is?

Conservation of mass applies to restriction digestion: sum of fragment lengths equals parental molecule length when digestion is complete and no small fragments are lost in gel. Double digestion that generates 1.9 kb and 2.9 kb bands indicates parental construct of 4.8 kb because no other bands are detected and both fragments are accounted for. This additive relationship allows calculation of unknown plasmid sizes, verification of successful cloning, and detection of partial digestion or star activity. Accurate size estimation using DNA ladder on agarose gel makes it possible to reconstruct map and confirm recombinant integrity.

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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Restriction Digestion & Mapping

How many fragments result from double digestion of circular DNA with 2 unique sites?

Circular DNA remains topologically closed, so a single unique restriction cut converts it into one linear molecule of unchanged length. A second unique cut at a different position divides that linear molecule into two distinct fragments. Counting bands on agarose gel therefore directly reveals number of cut sites when enzymes are unique. For circular plasmids, number of fragments equals number of sites cut. Two enzymes each cutting once generate two fragments whose sizes add up to total plasmid size, confirming double digestion and enabling circular map construction for vector analysis.

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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