Question

recombinant DNA experiment

Select the correct words from the drop-down menus for all 4 options ( 1 mark )

Q1) After adding the cell lysis buffer and incubating, neutralisation enables the separation of plasmid DNA from chromosomal DNA based on their different sizes. On neutralisation, the single–stranded DNA species of both chromosomal and plasmid origin (previously separated or denatured by alkali treatment) tend to re-anneal or ‘renature’, but…

(i) The Choose. (plasmid / bacterial chromosomal ) DNA can re-anneal faithfully and quickly due to its relatively Choose...(small large size). As a result, it renatures correctly and remains soluble.

(ii) In contrast, the Choose...(large/ small )molecules of Choose...(bacterial chromosomal/ plasmid) DNA cannot re-anneal correctly. Instead, they form a tangled mess with other denatured macromolecules (proteins and lipids) and SDS. Aggregates are insoluble, especially in the high salt concentration conditions present at this stage, which allows them to be removed by centrifugation in the next step.

Answer 1

1. (plasmid) DNA can re-anneal faithfully and quickly due to its relatively (small size). As a result, it renatures correctly and remains soluble.

(ii) In contrast, the (large )molecules of (bacterial chromosomal) DNA cannot re-anneal correctly.

Plasmids are generally small and renatures fastly and forms dsDNA. Chromosomal DNA are larger in size and it takes longer time to renatures.