If you had to perform this extraction using blood,
What type of cells would you ideally want to isolate for this extraction and why?
Would the genomic DNA isolated from blood differ from those isolate from cheek cells? Motivate your answer
Prof. Dawkins-Hall is right. I would like to add extra info:
1. You could simply use an erythrocyte lysis solution (NH4Cl or even deionized H2O, check the web for recipes) to get rid of them. This way your leukocyte yield should be higher since Ficoll gradient isolates only PBMCs and not PMNs, besides being more expensive.
2. PMNs are the most abundant nucleated cells in blood, so you might want to keep them to increase DNA yields.
3. Blood cells DNA might be different from cheek cells or other tissue cells only in a few cases: a) if your analyzing Immunoglobulin or T cell receptor genes (they are rearranged in lymphocytes due to VDJ recombination), b) if the individuals have a blood related pathology (i.e. leukemia), and c) if the individuals have a genetic disease with degrees of mosaicism like in congenital Down syndrome (trisomy 21).
Hope you find the info useful or interesting at least.
Dear colleagues, your opinions are very usefull, but I would add some points from me
1. Sometimes it is necessary to work only with whole blood because of special tasks like liquid biopsy. Yes, in these case You need plasma, not WBC, but you can't use cheek epithelium in these case.
2. Buccal epithelium is the best in the case of organization and conduction of any study on the sample of health population because of noninvasive cells collection way.
3. Finally, it is difficult to receive perfect DNA samples (I mean purification, integrity, concentration) from buccal mucosa for the goals of NGS and TGS.
What kind of organism? Mammals have de-nucleated red blood cells. However, lizards and birds retain nuclei in their red blood cells. The type of organism will change how much whole blood you should use.
In general, folks will use whole blood. It is impractical/unnecessary to do cell sorting for most labs.
All cells in the body have the same genomic DNA (OK, there are a few odd exceptions, but cheek cells are not one of them). As others said, the yield and purity of genomic DNA can vary depending on the source materials.
Luis Antonio Ochoa-Ramírez In case of diagnosis of leukemia, do we have to separate the WBC from Whole blood and proceed with the DNA extraction from WBCs only?
Ravi Tauran, that is more dependent in the DNA extraction method than in the pathology. There are DNA isolation protocols that use whole blood and others than the starter are leukocytes, the latter usually with greater yields.