Figure 1. The original N^nd-1 allele is present in the SAT N^nd-1 stock.

(A) DSC N^nd-1 stock is homozygous for the Harding-Theobald et al. [40] deletion, as the deletion 3′ primer does not yield the 290 bp PCR product. (B) SAT N^nd-1 stock contains the original N^nd1 allele, as the 290 bp PCR product is present at a low level (lane with white asterisk). (C) In a sub-sample of 9 iso-chromosomal lines isolated from the SAT N^nd-1 stock one is revealed as the original N^nd-1 chromosome (lane with white asterisk). Photographs of ethidium bromide stained agarose gels are shown. PCR included one 5′ N primer (5′ primer 1) and two 3′ N primers; one located downstream of the deletion (3′ primer 1 that yields the 670 bp product) and one inside the deletion (deletion 3′ primer that yields the 290 bp product from alleles without the Theobald-Harding et al. deletion). (D) PCR primers flanking the Theobald-Harding et al. deletion (5′ primer 1 and 3′ primer 2) yield PCR products of different sizes indicating that this deletion is present in the DSC N^nd-1 allele but not in the original N^nd-1 allele. A 307 bp product was expected with the Theobald-Harding et al. deletion (from the DSC N^nd-1 allele) and a 348 bp product was expected without this deletion (from the original N^nd-1 allele). -  =  no template control; M  =  marker DNA. (E) Schematic representation of the Theobald-Harding et al., deletion (∇), primers used determine its presence or absence in fly lines (arrow heads), and polymorphisms (↓p1 – p5) detected in the study (p1  =  CAA to CAG in the eighth Glutamine codon in the opa region; p2  =  CAA to CAG in the last Glutamine codon in the opa region; p3  =  G to C at position 8161; p4 =  a T deletion at position 8300; and p5 =  a T insertion at position 8544. Coding region polymorphisms p1 and p2 do not change the amino acid sequence, confirming the earlier report by others that there is no change in the amino acid sequence of the original nd¹ allele (FlyBase).