Figure 2.

The complexity of ‘omics’ fields in biological processes that contribute to the study and understanding of biological systems. There are more than 25 000 genes in the human genome, encoding ∼100 000–200 000 transcripts and 1 million proteins, whereas there are as few as 2500–3000 metabolites that make up the human metabolome (Botros et al., 2008). The genome is essentially invariant among cells and tissues, while the epigenome has a low/moderate temporal variance and influences both transcriptome and proteome. The transcriptome has a high temporal variance and is translated into the proteome differentially in different tissues and physiological states, affecting the metabolome in a tissue-specific manner. This ‘simple’ model is modulated by multiple factors: (A) differential splicing that can be affected by the proteome; (B) post-translational modification of proteins; (C) transcription factor binding; (D) receptor ligand binding and (E) environmentally induced factors (adapted from Gracie et al. 2011; Bellver et al. 2012).