Table 3.

The abundance of transcription units in human, mouse, and rat


Transcription units

Polyadenylated

Tandem poly(A) sites

Composite exons

Hidden exons

Truncated exons

Alternatively polyadenylated
Human 13,268 5521 1084 650 794 6535 (49%)
Mouse 9227 2532 233 138 355 2898 (31%)
Rat
2611
621
87
57
59
710 (28%)

[i] The percentages of alternative polyadenylation are calculated relative to the polyadenylated transcription units.