Table 1.

Frequency of Insertion (Ins) and Deletion (Del) Events

	Ins + Del	Ins	Del	Sum Ins	Sum Del	Mean Ins length	Mean Del length
Rat	855	320^a	535^a	664^b	951^b	2.1	1.7
Mouse	888	423	465	828	860	2.0	1.8
Total	1743	743^c	1000^c	1492^d	1811^d	2.0	1.8

Sum Ins and Sum Del denote the total number of codons inserted and deleted, respectively. Superscript characters indicate significant (P < 0.0001, two-tailed Fisher's exact test) departures from the null hypothesis that insertions and deletions occur with equal frequency (columns Ins and Del) or encompass an equal total length of sequence (columns Sum Ins and Sum Del).

Occurrence and Consequences of Coding Sequence Insertions and Deletions in Mammalian Genomes