A cell's developmental stage and type have a significant impact on the amount and makeup of its RNA.
tRNAs and rRNAs make up the majority of RNA molecules.
Although the exact amount varies depending on the cell type and physiological condition, mRNA only makes about 1–5% of the total cellular RNA.
A single mammalian cell has about 360,000 mRNA molecules, which are made up of 12,000 distinct transcripts, each of which has a normal length of about 2 kb.
Some mRNAs make up 3% of the total mRNA pool, while others make up less than 0.1 percent.
These uncommon or low-abundance mRNAs may only contain 5–15 copies per cell.