a1 MRC Radiobiology Unit, Harwell, Didcot, Oxon OX11 0RD, England
Examination of the eyes with a slit lamp revealed that 101/H mice had a coloured cataract. Crosses to C3H/HeH indicated that this was inherited as a single recessive gene which we have designated lop-2 (lens opacity-2). The related strain 129/Sv-SlJ-CP had a phenotypically identical cataract and presumably also carries the lop-2 gene. CBA/H, CBA/CaH- + /p, CBA/H-kd and CBA/H-T6 mice had a bright white or white/green cataract that typically extended from the nucleus to the anterior cortex of the lens. Crosses to C3H/HeH indicated that this was inherited as a semi-dominant gene. However, other crosses raise the possibility that the CBA cataract is also caused by lop-2. If so, the expressivity (and penetrance of the heterozygote) is affected by genetic background. Neither lop-2 nor the gene responsible for the CBA cataract was linked to contrasted (Slcon) on chromosome 10, so these are distinct from the Lop (lens opacity) gene. Further studies of genetic linkage are needed to clarify whether lop-2 is responsible for both the 101/H and CBA/H cataracts.
(Received February 08 1985)
p1 Present address: Department of Obstetrics and Gynaecology, University of Edinburgh, Centre for Reproductive Biology, 37 Chalmers Street, Edinburgh EH3 9EW.