Get expert answers to your genetic research questions. Connect with scientists and researchers worldwide.
Latest Questions
What are the requirements for sequencing primers?
General requirements for sequencing primers:
(1) Specific binding to the sequencing template, with no more than 4 base mismatches.
(2) Must not contain mixed bases.
(3) Length: 17–25 bases.
(4) High purity, preferably PAGE purified.
(5) Dissolved in ddH₂O, not TE buffer.
How to determine plasmid DNA concentration and purity?
We use horizontal agarose gel electrophoresis, adding 0.5 µg/mL EB to the gel, and include a standard sample of known concentration. After electrophoresis, compare the brightness under UV light to judge concentration and purity. This method more directly and accurately assesses whether the sample contains genomic DNA, RNA, etc., and can also distinguish different conformations of the extracted plasmid DNA.
The three conformations of plasmid DNA refer to: during the plasmid extraction process, due to various factors, the supercoiled covalently closed circular (CCC) plasmid can have one strand break, becoming open circular (OC). If both strands break, it becomes linear (L). These three forms have different migration rates. Typically, supercoiled (SC/CCC) migrates fastest, followed by linear (L), and open circular (OC) migrates slowest.
Using a UV spectrophotometer or the EB-standard DNA comparison method only detects the concentration of the extracted product. However, due to potential interference from RNA, protein, genomic DNA, etc., in the extracted plasmid DNA, the concentration value obtained may be meaningless.