EDITGENE / MOLECULAR SYSTEMS / LAB 02 ← Genome Atlas
CRISPR Technologies / Scientific Laboratory

Molecular
tools.
New possibilities.

Explore the molecular architecture of CRISPR-Cas technologies. From Cas9 and Cas12a DNA nucleases to RNA-targeting Cas13 systems, discover how programmable recognition connects nucleic acid sequences to biological research.

Enter the Mechanism Laboratory
01 / Interactive Molecular Instruments

Observe the mechanism.

Select a CRISPR system to compare DNA recognition, RNA recognition and cleavage mechanisms.

Instrument / Nucleic Acid Targeting Three Systems / Comparative Display
NGG Cas9 Guide RNA PAM DOUBLE-STRAND BREAK FIG. 01 / SP-CAS9 / SCHEMATIC
TTTV Cas12a PAM crRNA STAGGERED CUT FIG. 02 / CAS12a / SCHEMATIC
Cas13 crRNA RNA CLEAVAGE SINGLE-STRANDED RNA FIG. 03 / CAS13 / RNA TARGETING
EditGene / Molecular Architecture Educational Figures / Not to Scale

Scientific note: these illustrations are simplified conceptual representations. PAM preferences, cleavage behavior, targeting requirements and collateral activity vary across Cas orthologs and engineered variants.

02 / Target Recognition Architecture

How does CRISPR find a molecular target?

Recognition is governed by the relationship between the guide RNA, target sequence and properties of the Cas effector. For many DNA-targeting systems, a nearby protospacer-adjacent motif (PAM) is also essential.

Diagram 04 / Guide RNA + DNA SpCas9 Example
CRISPR-Cas9 targeting and PAM diagram An illustrative target DNA sequence, paired guide RNA, NGG PAM, and Cas9 recognition region. Sequences are schematic and not intended as a guide design example. A C T G A C G T A A G G PAM / NGG GUIDE RNA TARGETING REGION TARGET DNA
DNA Guide RNA PAM

Conceptual targeting diagram. Only selected bases are labeled, and the displayed segment is not a complete guide-target duplex. The PAM is part of the target DNA, not the guide RNA. Strand orientation and sequence spacing are simplified.

Recognition / 01

Guide RNA

The guide contains a targeting region complementary to the nucleic acid target. Its sequence influences recognition and specificity. Guide structure differs between CRISPR systems.

Recognition / 02

PAM Requirements

Many DNA-targeting Cas proteins require a short adjacent DNA motif. SpCas9 commonly recognizes NGG, while commonly used Cas12a orthologs can recognize TTTV motifs. Requirements are variant-dependent.

Recognition / 03

RNA Target Recognition

Cas13 recognizes RNA rather than genomic DNA. Some Cas13 systems have protospacer-flanking sequence preferences, but these are not equivalent to a universal DNA PAM.

03 / Molecular Substrate Comparison

DNA targeting and RNA targeting are fundamentally different.

CRISPR systems can act on different biological molecules. The target substrate affects the nature of the modification, its persistence and the biological questions that can be investigated.

TYPE II / CAS9

DNA Cleavage

GUIDE RNA + DNA + PAM

Cas9 can cut genomic DNA, leading to repair-dependent insertions, deletions or template-directed changes. Catalytically inactive Cas9 derivatives can also be used for gene regulation studies.

TYPE V / CAS12a

Alternative DNA Targeting

CRRNA + DNA + PAM

Cas12a has distinct DNA recognition and cleavage properties. Many Cas12a enzymes generate staggered breaks and can process CRISPR RNA arrays for multiplex targeting.

TYPE VI / CAS13

RNA Targeting

CRRNA + RNA TARGET

Cas13 can target RNA transcripts without directly modifying genomic DNA. Engineered derivatives can be applied to RNA detection, imaging or certain RNA-editing strategies.

04 / Scientific Research Applications

What can researchers investigate with CRISPR technologies?

CRISPR methods support a wide range of molecular and cellular research. Their applications differ according to the Cas enzyme, engineered components and biological system.

01

Functional Genomics

Targeted perturbation and pooled screening approaches help researchers study gene function, regulatory networks and cellular phenotypes.

02

Disease Modeling

Editing defined genetic regions can help establish cellular and organismal models for investigating disease mechanisms.

03

CRISPR Interference & Activation

Catalytically inactive Cas proteins can recruit regulatory factors to modulate gene expression without conventional DNA cleavage.

04

Plant Genome Engineering

DNA-targeting CRISPR methods support research into plant gene function, development and agriculturally relevant traits.

05

RNA Research

Cas13-based platforms can investigate RNA abundance, transcript function, localization and RNA-targeted molecular regulation.

06

Molecular Detection

Certain Cas12 and Cas13 systems exhibit target-triggered collateral cleavage properties that are used in nucleic acid detection research and assay development.

05 / Experimental Interpretation

Understanding the limits of molecular precision.

CRISPR technology is powerful but not infallible. Reliable scientific interpretation requires attention to targeting specificity, biological context, editing outcomes and method-dependent limitations.

01 Off-Target Activity

Guide-directed systems may recognize unintended sequences with sufficient similarity or permissive recognition features. Their frequency and significance depend on the effector, guide, substrate and biological model.

Research implication: specificity cannot be established from computational prediction alone. Appropriate empirical validation is important.

02 DNA Repair Outcomes

DNA cleavage does not determine a single inevitable editing result. Cellular repair can produce different insertions, deletions and other sequence changes.

Research implication: allele distributions, larger on-target changes and genomic integrity may need evaluation.

03 Delivery & Cellular Context

Performance varies with cell type, chromatin state, component delivery, expression duration and target accessibility.

Research implication: results obtained in one cell model should not be assumed to transfer directly to another.

04 Cas13 Collateral Activity

Target recognition can activate collateral RNA cleavage in some Cas13 systems. The extent depends on ortholog, engineering and biological context.

Research implication: activity useful in molecular detection may require different evaluation when targeting RNA inside cells.

05 Functional Validation

Detecting molecular modification does not necessarily establish a predicted biological phenotype. Edited populations may contain different genotypes and responses.

Research implication: molecular characterization should be complemented by appropriate functional assays, biological controls and replicates.

06 / Scientific Reference Library

Explore the research behind the mechanisms.

Primary research and specialist reviews provide the foundation for understanding CRISPR-Cas structure, targeting and applications.

The molecular graphics on this page are original conceptual illustrations, not atomic structures or experimentally collected data.

Addgene — CRISPR Guide Cas9, Cas12a, RNA Guides, PAMs Structures, Mechanisms and Applications of RNA-centric CRISPR–Cas13 Nature Chemical Biology / 2024 Assessing and Advancing the Safety of CRISPR-Cas Tools Nature Communications / 2023
Continue the EditGene Learning Pathway

From CRISPR recognition to precision engineering.

FOUNDATION / 01 Genetic Foundations DNA, genes, chromosomes and genetic variation. NEXT / 03 Precision Editing Base editing, prime editing and advanced molecular systems. EXPLORE / 04 DNA Repair NHEJ, HDR and repair-dependent editing outcomes.

EditGene provides educational scientific information. Content is not a clinical protocol, medical recommendation, or validated experimental procedure.