Merle and roan
The first merles bred in the UK; recessive yellow merle bucks bred by Cait Walgate
Roan/merle is a recessive gene, which must be homozygous in order to be expressed. There have been incidences in the US where people have claimed that roan/merle has acted as a dominant gene, but this has not been proven and is not common. The variety first emerged in the US in the 1980s and is now in the hands of exhibition breeders across the country.
Merles are believed to be the result of an unstable gene where parts of the mouse's coat revert to the undiluted colour. This could also explain why the markings are often along the spine or the middle of the belly (because they begin in the embryo at the midline). Merles do not breed true and it is luck as to whether each mouse develops these undiluted patches in utero. One of the first breeders of roan and merle mice stated "when pairs of dark-marked animals are mated, approximately 40% (overall) of the offspring will have dark marks and 60% will be unmarked roans. (Out of 256 babies from such matings, 104 had dark marks, 152 did not). Similarly, when two unmarked roans are mated, dark-marked babies may show up in their litters (though the percentage is much less over all)".
Roan markings usually develop by around six weeks of age. Some mice clearly show ticking when they start to grow fur, whereas some show a small amount of ticking at this stage that continues to develop until around six weeks of age, sometimes with a dramatic change taking place between weeks five and six.
Until recently merle and roan was not available in the UK. However it was imported first into Germany and then spread throughout Europe, including Holland and the UK in 2014.
Merles are believed to be the result of an unstable gene where parts of the mouse's coat revert to the undiluted colour. This could also explain why the markings are often along the spine or the middle of the belly (because they begin in the embryo at the midline). Merles do not breed true and it is luck as to whether each mouse develops these undiluted patches in utero. One of the first breeders of roan and merle mice stated "when pairs of dark-marked animals are mated, approximately 40% (overall) of the offspring will have dark marks and 60% will be unmarked roans. (Out of 256 babies from such matings, 104 had dark marks, 152 did not). Similarly, when two unmarked roans are mated, dark-marked babies may show up in their litters (though the percentage is much less over all)".
Roan markings usually develop by around six weeks of age. Some mice clearly show ticking when they start to grow fur, whereas some show a small amount of ticking at this stage that continues to develop until around six weeks of age, sometimes with a dramatic change taking place between weeks five and six.
Until recently merle and roan was not available in the UK. However it was imported first into Germany and then spread throughout Europe, including Holland and the UK in 2014.
