520 APPENDIX 



as different. Example: DBA/1 and DBA/2. Appropriate checks to avoid duplica- 

 tion should be made before this type of symbol is adopted. 



5. Coisogenic stocks. — Coisogenic stocks produced by the occurrence of a single 

 major mutation within an inbred strain, or by the introduction of a gene into an inbred 

 background by a series of crosses, shall be designated by the strain symbol and, when 

 appropriate (see rule 7), the substrain symbol, followed by a hyphen and the genie 

 symbol (in italics in printed articles). Example: DBA/Ha-Z). When the mutant 

 or introduced gene is maintained in the heterozygous condition, this may be indicated 

 by including a + in the symbol. Examples: A/Fa- + c, C3H/N-+ W 1 . 



When a coisogenic strain is produced by inbreeding with forced heterozygosis, 

 indication of the segregating locus is strictly optional. Examples: 129 or 129-c ch c 

 (129 is customary) ; SEAC-rf+/ + w or SEAC/Gn. 



In the case of coisogenic stocks produced by repeated crosses of a dominant gene 

 into a standard inbred strain, it may be desirable to indicate the number of backcross 

 generations. Example: C57BL/6-+ J>P(N8). The first hybrid or F x generation 

 should be counted as generation 1, the first backcross generation as generation 2, and 

 so forth. 



6. Substrains developed through foster nursing, ova transfer, or ovary transplant.— Substrains 

 developed by foster nursing shall be indicated by appending an " f " to the strain symbol. 

 Example: C3Hf. The strain used as foster parent may be indicated if desired by the 

 addition of its symbol or an abbrevation for the same. Example: C3HfC57BL or 

 C3HfB (C3H fostered on C57BL) . In like manner, strains developed through egg trans- 

 fer or ovary transplant shall be indicated by adding an "e" or "o", respectively. 

 Example: AeB (A ova transferred to C57BL). When the symbol for fostering or 

 transfer might be confused with an adjoining substrain symbol, it may be used in a 

 subscript position. Example: A/He f B (Heston substrain of A fostered on C57BL). 



7. Compound substrain symbols for stocks of complex origin. — When a stock has been 

 produced by manipulation of a standard inbred strain, as, for example, by fostering 

 or by introduction of a foreign gene, compound substrain symbols may be necessary. 

 In general, the elements of such a compound symbol should be arranged in an order 

 indicating a historic or temporal sequence. Specifically, different positions should 

 be interpreted as follows : 



a. Substrain symbol that immediately follows strain symbol: Examples: BALB/cf, 

 DBA/2eB, C3H/Ha-p. In this position the substrain symbol (c, 2, or Ha in examples 

 given) designates the substrain which was fostered or otherwise manipulated, or in 

 which a mutation occurred. 



b. Substrain symbols following symbol for manipulative process or introduced 

 gene: Substrain symbols in this position refer either to the person performing the 

 fostering or other manipulation, or to the person or laboratory currently maintaining 

 the strain, or to both. The symbol or symbols may or may not be immediately pre- 

 ceded by a slant line. Examples: DBA/2eB/De or DBA/2eBDe (strain derived from 

 ova of DBA/2 transferred by Deringer to C57BL, maintained by Deringer); C3H/ 



