Why would we use RNA for barcoding when DNA is much easier & cheaper? Got any references to get started?

Thanks Dr. Katie A S Burnette for your response.

In fact, I wanted to mention some references on the topic of RNA barcoding in one of my book chapters (written in Bengali) on animal classification and systematics. In this connection, I’ve already discussed DNA barcoding there and included several relevant references, but I’ve been unable to find any work specifically on RNA barcoding used for species identification. While I have come across references related to RNA barcoding, all are on cell-level identification within complex tissues but not on species identification.

Thank you once again for your kind response.

That is because RNA barcoding is not used for species identification.

I think the issue is that the term "barcoding" refers to two very different applications.

1. Species identification by genetics. Several regions were picked due to their evolutionary "clock speed" to identify organisms. The term "barcode" is an analogy. The inventors meant that using a small region of DNA to determine genetic identity is similar to how the UPC pattern (Universal Product Code; also called a "barcode") on an item you are buying is scanned to identify the item (e.g. UPC barcode on the label of a can of fruit).

2. Molecular technique used to distinguish molecules from different sources. It's usually used for a high-throughput sequence analysis method. You put a region of DNA molecules of your choice (the "molecular barcode") on the DNA or RNA from a particular sample. Each sample gets a unique sequence. You can run the samples all in parallel & then use the "molecular barcode" sequence to parse them apart using software.

Hopefully we'll have a new term for one or the other so there is less confusion. It's like how "RT-PCR" used to refer to both reverse-transcriptase PCR and real-time PCR. Now, RT-PCR is used just for reverse-transcriptase and we use qPCR (quantitative PCR) for any reaction that is measured in real-time instead of as an endpoint.

Thanks again, Dr. Katie A. S. Burnette, for your further response.

So, I should write it like this (in Bengali): Although the RNA barcoding technique can be used for species identification, due to certain challenges and costs, it is usually not preferred for this purpose.

By the way, I came across a company that mentions one of their services as follows (https://ohmx.bio/applications/microbiome-analysis-2/): "Direct DNA or RNA sequencing enables base modification identification in relation to microbiome analysis." However, I am unsure whether they specifically offer RNA barcoding for species identification, which is what I am looking for.

Best regards,