Table 1. Frequency of occurrence of internal NotI sites in rat brain cDNA clones obtained by RC.

cDNA Insert size (bp)a	Number of NotI sites per cDNA		cDNA Insert size (bp)a	Number of NotI sites per cDNA
	1	2	0	Total
500–1000	15(2)b	1	0	16
1000–2000	76	0	1	77
2000–3000	19	2	2	23
3000–4000	57	4(2)c	0	61
4000–5000	13	1	0	14
5000–6000	0	1	0	1
Total	180	9	3d	192

^aBecause plasmids harboring 3–4 kb cDNA inserts in a supercoiled form co-migrated with those harboring 1–2 kb cDNAs in an open circular form on agarose gel electrophoresis, the size distribution of analyzed cDNA inserts had two peaks, at 1–2 and 3–4 kb, as shown.

^bThe number of plasmids found as dimers is shown in parentheses.

^cThe number of chimeric clones is shown in parentheses.

^dOne plasmid carried a mutation at the position corresponding to a NotI site while two other plasmids were accidentally recovered attP donor plasmids.