Where do these genomics words come from?

A short field guide to cfDNA, methylation, fragmentomics, EM-seq, and Reactome

Five names, five different kinds of history

Some scientific terms describe an object, others a chemical change, a field, a method, or a database. Knowing which is which makes the vocabulary much easier to remember.

From DNA and methyl marks to fragments and pathway networks: a visual tour of the vocabulary. This is a conceptual illustration, not a literal molecular-scale scene.

Term	Literally	Where the name came from	What it means here
cfDNA	cell-free DNA	A plain description: DNA found outside intact cells. Mandel and Métais reported nucleic acids in human blood in 1948.	Short DNA molecules circulating in plasma; only a fraction may come from diseased tissue.
Methylation	Addition of a methyl group, \(\mathrm{-CH_3}\)	A chemistry term, not a genomics brand. In 1948 Rollin Hotchkiss detected 5-methylcytosine in animal DNA and called the unexpected spot “epicytosine.”	A chemical layer on DNA, commonly measured at cytosines in CpG sites.
Fragmentomics	Fragment + -omics	Built in the style of genomics and proteomics: study the fragment population as a system. The name became established as cfDNA length, end, and genome-wide cleavage patterns emerged as biomarkers in the 2010s.	Reading the size, ends, motifs, and genomic positions of cfDNA—not just its sequence.
EM-seq	Enzymatic Methyl-seq	A method name for enzymatic methyl sequencing, introduced as a gentler alternative to bisulfite conversion and described in 2021.	Enzymes distinguish modified from unmodified cytosines before sequencing, helping preserve scarce cfDNA.
Reactome	A name centered on biological reactions	The open pathway project was founded in 2003. Its reaction-first organization distinguishes it from a simple list of genes.	A curated map used to ask which biological reactions and pathways are represented by a result set.

A cabinet of genomics ideas: plasma fragments, methyl marks, enzymes, and reaction networks displayed as objects of discovery.

TipA quick memory trick

cfDNA is the material; methylation is a mark; fragmentomics is a way of reading molecule shape; EM-seq is a laboratory method; Reactome is a knowledgebase for interpretation.

The dates mark early reports or project milestones—not the moment each modern meaning appeared fully formed. Scientific vocabulary usually settles gradually as methods and communities develop.

Explore the cfDNA history · See the landmark 2019 fragmentation study · Read the EM-seq paper · Visit Reactome

What is fragmentomics? → · What is EM-seq? → · What is Reactome? →