Biology is Not Memorisation

 I’ve never been good at memorising things for their own sake. That’s probably why I never experienced biology as memorisation.

Actually, let me qualify that: Biology is not only memorisation, but maybe involves some degree of it. To study life’s components, they need to named, and then arranged in some logical order. This logical order changes depending on the question at hand. For example a protein can be a sequence of amino acids, a transcription factor or a signaling molecule, depending on the context and question. So you do at the outset need some memorisation but that’s basically not what biology is about. It’s about understanding relationships. I only very superficially understand category theory but I think it’s a subfield of math that has the most in common with how biology works, as it seems to be about relationships between carefully defined objects then the objects themselves.

In bio, much like in math, definitions are everything. In single cell RNA-seq experiments clusters of cells are annotated as specific cell types using cell type specific marker genes. The presence of these genes and the clustering by RNA types and count ensures that cells are mapped to the correct types. This illustrates something important about biological measurement: the need to be stable enough to be useful but flexible enough to accommodate new measurements.

By that I mean the following: for decades individual cell types were annotated by specific marker genes in the absence of ways to quantify the whole transcriptome. Now with the advent of technologies such as scRNA-seq we can simultaneously measure the transcriptomes of millions of cells. We need to be able to map these to the same objects that were studied for decades, so we use the marker genes to annotate. What this says about definitions is that some definitions remain consistent over decades of study. Others are redefined as technology improves. All of this to say: a cell type is not a platonic object. It is a node in a web of relationships that gets refined as the web becomes more detailed.