A collection of full-length mRNAs , ESTs or both. A component of a genomic database. A cluster contains any of the following:

• Full-length mRNAs
• Full-length mRNAs and EST sequences
• EST sequences only

Two sequences are grouped in a UniGene cluster if their similarity exceeds a defined threshold:

• Minimum homology
• Minimum sequence overlap

Two sequences are grouped in a subcluster if their difference does not exceed a maximum threshold.