IB Biology Topic D2.2.5: Differences Between the Genome, Transcriptome and Proteome of Individual Cells Notes

The Genome Is the Same in Every Cell, but the Transcriptome and Proteome Differ

1. Every somatic cell in an organism contains the same genome, the complete set of genetic instructions.
2. However, no cell expresses all of its genes at once.
3. The pattern of gene expression a cell uses is what determines how it differentiates.

Three Levels of Information: Genome, Transcriptome, and Proteome

1. Genome
   1. The complete set of DNA in a cell, essentially the same in all somatic cells of the organism.
2. Transcriptome
   1. The full set of mRNA molecules transcribed from the genome at a given time, which varies between cell types and over time.
3. Proteome
   1. The full set of proteins present in a cell at a given time, which also varies between cell types and over time.

Cells Differ Because They Express Different Genes, Not Different Genomes

1. Selective gene expression
   1. Each cell transcribes and translates only the genes needed for its specific function.
2. Cell differentiation
   1. Specialised cells such as muscle cells and neurons express unique sets of genes, giving each a distinct transcriptome and proteome.