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Plasmid Copy Number Formula:
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Plasmid copy number (CN) refers to the number of copies of a plasmid present in a single bacterial cell. It's a crucial parameter in molecular biology that affects gene expression levels and plasmid stability.
The calculator uses the following equation:
Where:
Explanation: The equation is based on the principle that each PCR cycle represents a doubling of the target sequence. The difference in Ct values between genomic and plasmid DNA reflects their relative abundance.
Details: Knowing plasmid copy number is essential for experimental design in molecular biology, as it affects gene expression levels, plasmid stability, and the yield of plasmid DNA preparations.
Tips: Enter the Ct values obtained from qPCR experiments for both genomic and plasmid targets. The values should be from the same sample and amplification should have similar efficiencies.
Q1: What is a typical plasmid copy number?
A: Copy numbers vary by plasmid type: low-copy (1-10 copies/cell), medium-copy (10-20 copies/cell), and high-copy (20-100+ copies/cell).
Q2: Why use qPCR for copy number determination?
A: qPCR provides a sensitive and quantitative method to compare relative amounts of genomic and plasmid DNA in the same sample.
Q3: What factors can affect copy number accuracy?
A: PCR efficiency differences between targets, DNA extraction efficiency, and growth conditions can all affect results.
Q4: Should I use genomic DNA or plasmid DNA standards?
A: For most accurate results, use genomic DNA as standard for genomic target and plasmid DNA as standard for plasmid target.
Q5: Can this method be used for other replicons?
A: Yes, the same principle can be applied to calculate copy number for any extrachromosomal element relative to chromosomal DNA.