DNA Extraction and Quantification Discussion PP

The average A260/280 ratio of 2.05 for the untreated samples is consistent with RNA, indicating presence of RNA in these samples, as expected.  The average A260/280 ratio for RNase treated samples was 1.60, while the accepted ratio for pure DNA is approximately 1.8.  This is slightly low to be convinced that the RNase treated sample is pure DNA.  The 260/230 ratio average of 0.60 for RNase treated samples further justifies the impurity of the samples, because a pure nucleic acid should have a 260/230 ratio that is higher than the 260/280 ratio [7].  On the gel, the consistent presence of bands slightly above the 10,000 base pair marker indicates the presence of genomic DNA in the samples.  In the RNase untreated samples, the fields of discoloration below the 500 base pair marker indicate the presence of RNA.  The RNase treated samples did not show these fields, indicating that the RNase worked to degrade the RNA to small enough lengths such that it was unnoticeable on the gel.  Although the RNA did not appear on the RNase treated gel, small RNA fragments were still in the solution even after RNase treatment because nothing was done to remove them.  This fact likely helps to explains the NanoDrop results indicating impurities for the RNase treated samples, although it is possible that there were additional cellular components left over as well.  The calculated amount of nucleic acids extracted was 15,720 ng.  The gel indicated the presence of both DNA and RNA in the untreated samples of the extract, and NanoDrop measurements indicated impurities that include RNA and possibly other cellular components.  Therefore, the actual amount of genomic DNA extracted from B. distachyon is likely far less than this value.