Fig 1. Classical mouse strains typed for 31 P-MLVs and grouped according to known breeding history.

Substrains AKR/N and AKR/J, and substrains C57BL/6 and C57BL/10 carry identical ERVs, whereas the two CBA substrains differ for six ERVs likely due to genetic contamination [37]. The SIM.R Fv1^b congenic differs from its SIM progenitor in the presence of 6 ERVs found in the Fv1^b donor strain, three of which are linked to Fv1. ^a+, presence; -, absence; L, solo LTR; H, heterozygous; ND, not done.