Question

So, I would like to ask, why don't we use just DNA hybridization instead of PCR primer amplification to diagnise some illness?

I know, when you have a really small amount of DNA from virus or cell you need to amplifie it, so you can do some hybridizations. But I cannot find out, why you need to amplifie it when you have like 10 ml of substance, where the amount of cells or viruses can be really high.

For instance, when you are trying to diagnose some chromosomal aberation you don't amplifie the DNA, so you do just hybridization, but when you are trying to detect coronavirus you use PCR, why?

I have all the information from Genetics by Eduard Kočárek (Scientina 2008) - so now you know the literature my question is based on.

Answer 1

PCR is preferred for diagnosing certain diseases because of its high sensitivity and ability to rapidly amplify even minuscule amounts of DNA, enabling detection of pathogens like viruses even when present in low numbers. Additionally, PCR does not require DNA purification or organism culture, which speeds up the diagnostic process. This makes it advantageous for detecting systemic infections and useful in forensic applications.

Step-by-step explanation:

Why PCR is Preferred Over DNA Hybridization for Certain Diagnoses

The use of Polymerase Chain Reaction (PCR) instead of straight DNA hybridization for diagnosing illnesses, such as viral infections or specific diseases, is primarily because PCR is an exceptionally sensitive technique. It can detect and amplify minute amounts of DNA in a sample, making it ideal for cases where the pathogen or genetic aberration is present in very low numbers. For instance, the diagnosis of viral infections like coronavirus relies on PCR amplification because it allows for the rapid and specific detection of the virus even in instances when the viral load may be low. Moreover, PCR is adept at amplifying DNA to sufficient quantities for clear analysis, which is essential for conditions such as chromosomal aberrations, genetic fingerprinting, or disease susceptibility like breast cancer.

Another key reason PCR is chosen over just hybridization is that it can be performed quickly without the need to culture the organism or purify the DNA, which is a significant advantage in time-sensitive situations. Beyond the medical field, PCR has broad applications in forensic science for genetic fingerprinting through analysis of short tandem repeats (STRs), where specificity and the ability to amplify DNA from tiny samples are crucial.

When diagnosing illnesses that have a high number of cells or viruses in a given substance, PCR ensures that even if only a few of those cells or viruses contain the target DNA sequence, they can be detected and accurately quantified. This is particularly true in cases like systemic infections where detecting the pathogen rapidly can guide treatment decisions. Therefore, while hybridization may work for conditions with ample target DNA, PCR provides a more reliable and powerful tool for diagnosis in varied circumstances.