sgRNA, the single guide RNA, is the one-molecule format of a CRISPR guide: the target-specific spacer and the Cas-binding scaffold joined into a single RNA. It is what most protocols expect, what most vendors sell as a standard product, and the format that carries the most useful chemical modifications. This page is for the person who has designed a target and now has to decide whether to buy the sgRNA synthetic, transcribe it, or express it, and how to read the vendor prices for the synthetic route.
What the molecule is and why it is long
A single guide RNA is roughly a hundred bases: a short spacer that matches the genomic target and a longer scaffold that folds into the hairpins the Cas protein grips. That length matters commercially, because chemical RNA synthesis gets harder and more expensive with every base and the fraction of full-length product falls. Vendors therefore price sgRNA as its own product line rather than as a long RNA oligo, with the scaffold fixed and only the spacer changing from order to order.
Synthetic sgRNA: when it pays for itself
Chemically synthesised sgRNA arrives full length, quantified, and with end modifications that protect it inside the cell. It is the format for ribonucleoprotein delivery, for primary and stem cells, for in vivo work and for any experiment where a clean, immediate, transient edit matters more than the cost per guide. It is also the right choice when a lab wants to remove its own transcription step as a variable. The price per guide is the highest of the options and the comparison on this site shows how far vendors differ.
In vitro transcribed and plasmid expressed sgRNA
Transcribing sgRNA from a DNA template with a phage polymerase costs a few reagents per guide and suits a lab screening many targets in cell lines. The product is unmodified, carries a 5' triphosphate that some cells sense, and needs cleanup. Expressing the sgRNA from a plasmid or lentiviral vector alongside Cas is the cheapest per target for pooled screens and stable lines, at the cost of persistent expression and integration. Choose by delivery route and cell type first.
Comparing sgRNA vendors
Compare the same thing: the same modification pattern (usually modified at both ends), the same purification, the same nanomole amount and the same certificate. Some vendors quote a low base price with modification, purification and a mass spectrometry report as add-ons; others quote one complete price. The RNA synthesis pages on this site record the published figures per vendor, verified on the vendor's own page and dated, so the add-on arithmetic is visible before you order.
Questions people ask about sgrna
Is sgRNA the same as guide RNA?
sgRNA is one format of guide RNA: the single-molecule fusion of crRNA and tracrRNA. Guide RNA also covers the two-part format.
How much sgRNA do I need?
It depends on the delivery method; ribonucleoprotein electroporation uses more per reaction than lipid transfection. Vendors sell in nanomole tiers and the smallest tier covers a typical pilot.
Can I order sgRNA for any Cas enzyme?
Most vendors sell Cas9 sgRNA as standard and Cas12a guides as a separate product, because the scaffold differs. Check the enzyme before you order.
Should sgRNA be modified?
For primary cells, in vivo and RNP work, yes. For plasmid-based editing the guide is expressed, so the question does not arise.