Some novel intron positions in conserved Drosophila genes are caused by intron sliding or tandem duplication

Table 1 Properties and origins of NIPs.

nt	FBgn	apomorphic introns	Properties typical for intron sliding					Properties typical for tandem duplication
			No intermediate, intron-less state in the tree	Multiple-of-three NIP distances that made a stepwise intron shift possible	Cryptic splice sites, occurring in NIP distance and supported by amino acid conservation	One-sided shifts or GYRGYR/NAGNAGs in some species	Significant sequence similarity between introns of both positions	Proto-splice site (AG/GY)	plesiomorphic introns not identifiable
probably migrated intron positions
3	3607	118-1	x	x		x
3	32261	55-0	x	x		x
3	37757	616-1	x	x		x	x
6	19809	255-0	x	x		x
6	35879	105-1	x	x	x		x
9	32821	1200-0	x	x	x
9	34221		x	x			x		x
12	33734	419-0, 423-0	x	x		x
15	1124	124-0	x	x	x
introns probably gained by tandem (exon) duplication
10	30661							x
21	29747		x	x				2x	x
30	38300		x	x				2x	x
30	50101	251-0	x	x				x
31	2526							x	x
NIPs of unknown origin
2	31216	1927-1, 1928-0	x						x
2	36142	456-0, 456-2	x		x
3	15572	4-2	x	x
3	32087	19-1	x	x
3	32504			x					x
3	52081		x	x					x
5	46689	16-2	x		x
6	31395		x	x					x
9	38302	65-2	x	x
14	35965	44-0	x
16	33686	53-2, 59-0	x						x
21	30055		x	x					x
22	32517	221-0	x
23	33247	45-2	x
24	34793	29-0	x	x
27	1185			x					x
28	31773	164-1	x
∑	31	25	27	21	5	5	3	7	11

"nt" means NIP distance in nucleotides. Note that each of the 9 NIPs resulting supposedly from intron sliding shows at least three of the expected properties and/or a significant sequence similarity between introns of both positions (Materials and Methods). Introns gained by tandem duplication show a proto-splice site. In addition, a plesiomorphic intron is not identifiable because both introns probably have been gained by the same duplication.

ISSN: 2730-7182