for each gene or marker, there is a total maxium possibility of two stars, one from each parent. the symbol _ = no star from it's parent
** x ** = **
** x *_ = **, *_
** x _ _ = *_
*_ x *_ = **, *_, _ _
*_ x _ _ = *_ ,_ _
_ _ x _ _ = _ _
some of the tests are for the same gene for the same change in the DNA code from the different companies, they just call them somthing different. the one's from ingenity are markers that have been shown to be linked to these traits which may or may not be the actual gene itself, but could be regulation, another gene. i haven't seen any data of steaks you could cut with say 3 lbs force (if there is actual other genes creating more tenderness) vs the i think average for no stars is around 11 lbs. one of the genes has two changes in the code in two separate locations, and are not totally additive (or subtractive?) for pounds necessary to cut the meat. each star is worth about 0.4 less pounds to cut the meat. combinations of stars produce different results, as different genes and different combinations produce different results.
look at each of the charts from the different companies. most companies use scales because people can understand them. they don't really understand markers that may be associated with traits, especially if the marker isn't yet determined to be within a gene. supposedly these companies are not marketing antagonistic markers which creates a whole ball of wax.
some people have complained that animals that have these carcass genes have not been the most phenotypically desirable animals, ie have smaller scotums, slab sided, pinched in the heart girth, but it may be that it totally due to chance, and like anything, if there isn't enough diversity in the beginning to select from, a type may get fixed. this can be changed obviously through introduction of different individuals, and will probably be the case as breeders breed up and down and up with the genes. since in the beginning, it was somewhat difficult to either produce a homzygous animal by breeding or discover one by testing, of course these animals got used a lot in those selection programs. however, over time, other animals with less stars but otherwise possessing desirable traits, will get introduced.
