Is there such thing as partial methylation of recognition sites for restriction
ID: 78170 • Letter: I
Question
Is there such thing as partial methylation of recognition sites for restriction enzymes. For example, a 6 kb plasmid is grown in two different strains. Then the plasmids are taken out and analyzed by gel electrophoresis. For strain 1 there is only a 3kb band, while for strain 2 there is a 3kb, 2kb, and 1kb band. What would be the explanation for strain 1 and why the restriction enzyme did not cut the same site as in strain 2. I thought methylation was supposed to occur at all restriction sites, but is there such thing as partial methylation? Or is there another reason for the outcome of strain 1?
Explanation / Answer
Restriction endonuclease digestion of DNA fragments takes place at specific sequences of the target strads. The plasmid is a DNA construct containing many restriction sequences. According to the information, similar plasmid has been inserted into two different strains and subjected to restriction digestion in them. The results obtained differential band patterns from these strains. One strain gave 3kb band and the other strain gave 1,2 and 3 kb bands. The explanation for this differential observation can be attributed to presence of different restriction enzymes in the two strains.
Partial methylation of restriction sites is a rarely observed phenomenon which takes place due to presence of salts in the medium or lowered activity of enzyme due to imbalance in homeostasis. But the observation in the experiment might have attributed to presence of more than one kind of restriction enzyme. For example, enzyme A might have cut the target DNA resulting in 3kb bands whereas the enzyme A might have cut the DNA at multiple sites leading to generation of multiple bands.
Thus, the observation resulted not due to partial methylation but probably due to presence of more than one types of restriction enzymes in the two strains.
Related Questions
drjack9650@gmail.com
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.