DNA dabbles

 Hi readers and welcome back to my blog post on DNA integrity index! Last time we looked at what DNA integrity index is and how it can be measured. Today, we will look at how DII can be used for diagnosing a disease like cancer. So how can a DII ratio help diagnose cancer?  When we say we use DII ratios for diagnosis, we mean that we are testing whether the values of ratios in patients are different from those in healthy people. Most studies say that the cancer patients have longer fragments than shorter fragments. Healthy people tend to have higher amounts of shorter fragments than longer fragments. So, the amount of long or short fragments of cfDNA in a person determines the DII value for that person. Let’s take a study by Pinzani and colleagues as an example.  In 2011, Pinzani and colleagues tried to find a suitable ratio for diagnosing melanoma. They isolated cell-free DNA from the plasma of 79 melanoma patients and 34 healthy people. They measured DNA fragments of ...

 In my last post, we looked at how concentration of cell-free DNA can be used as a biomarker for cancer. Today, we will look at another attribute of cell-free DNA: its integrity index.  First, how are the amounts of DNA measured? Usually, researchers use a technique called real-time PCR to measure the concentration of the DNA fragments. Now, PCR or polymerase chain reaction is a technique by which researchers create many copies of a DNA sequence. In short, during PCR, we add short DNA sequences called primers. We then select a gene sequence that we want to make copies of. We then use primers that bind to our gene of interest. An enzyme called DNA polymerase uses the gene sequence as a template. It extends the primers to create copies of the template DNA sequence. Real-time PCR is different from the standard PCR technique in that the number of copies of DNA are measured as they are created. Usually, fluorescent dyes are added which bind to the newly created DNA copies. A detec...