#### <a name="untypical"></a> Build RSEM references for untypical organisms
For untypical organisms, such as viruses, you may only have a GFF3 file that containing only genes but not any transcripts. You need to turn on `--gff3-genes-as-transcripts` so that RSEM will make each gene as a unique transcript.
Here is an example command:
```
rsem-prepare-reference --gff3 virus.gff \
--gff3-genes-as-transcripts \
--bowtie \
virus.genome.fa \
ref/virus
```
### II. Calculating Expression Values
To calculate expression values, you should run the
Estimate gene and isoform expression from RNA-Seq data.
rsem-calculate-expression - Estimate gene and isoform expression from RNA-Seq data.
=head1 SYNOPSIS
@@ -1125,7 +1121,7 @@ Using a logistic regression to combine TSS signals from multiple complementary d
=back
Parameters for all the above models are learned from a training set. For detailed explainations, please see prior-enhanced RSEM's paper. (Default: 'pk')
Parameters for all the above models are learned from a training set. For detailed explanations, please see prior-enhanced RSEM's paper. (Default: 'pk')