Genomic structure of murine Spam1 . (A) Overview of the Spam1 locus. Exons are boxed and numbered, with the size in bp shown above. Intron sizes in kb are given below. The approximate positions of the Spam1 ORF start and stop codons are indicated. The two Spam1 splicing variants are shown schematically below. ERV-derived sequences are shown in green, with other sequences in blue. The diagram is not to scale. A black bar indicates the region shown in more detail in Figure 5B. (B) Sequence and position of Spam1 exons 1 and 2 with respect to TE sequence. The sequence shown corresponds to mouse chromosome 6 co-ordinates 24623802 to 24624821 in the UCSC genome browser (May 2004 release). The solid line frames the sequence annotated as ERV1 MER34 pol sequence in the RepeatMasker database. Spam1 exon sequences are shown in upper case reverse type. Splicing variant 2 sequences are shown in bold type. The transcription start sites identified by 5'-RACE are underlined; splice donor and acceptor sites are italicized. A non-consensus CRE is shown in bold underlined type.