Mammalian Exon Size: Upper Limit

Keith Robison robison1 at
Mon Jun 8 10:38:26 EST 1992

bhjelle at (Brian Hjelle) writes:

>I am posting the following for a friend. His lab has sequenced
>an internal exon (not a 3' exon) of a new zinc finger gene and
>encountered open reading frame thru 700 bp of sequence, still
>open at the end of the sequenced region. He is concerned that
>this ORF is too large, indicating that he actually might have
>an (intronless) pseudogene. 

>Does anyone know how large the largest mammalian (internal)
>exons are? Any comments would be appreciated.


GenBank 71 contains the following internal, coding exons
of >1000nt:

          Gene                        exon (of)          nt

Human apolipoprotein B			26 (29)		7572
Mouse complement component C3		 3 ( 4)		4580
Human lactase phlorizin hydrolase	 8 (17)		1551
Human butyrylcholinesterase		 2 ( 4)		1525
Mouse episialin				 2 ( 7)		1304*
Mouse mucin				 2 ( 7)		1301*
Rat neuronal nicot. acetylcholine rec.   5 ( 6)         1030

* may be the same gene

This list may not be comprehensive -- exons would be missed
if they are the first or last exon in an entry which
had not been completely sequenced.

Keith Robison
Harvard University
Program in Biochemistry, Molecular, Cellular, and Developmental Biology

robison at 

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