somatic mutation

Heritage · August 14, 2013

Scott, you are correct about the possibility of the pink fruit not being stable. I had my previous red-to-yellow example on the brain when I said the pink fruit would produce all stable/pink fruit. In the case of a red-to-yellow somatic mutation all of the yellow fruit will produce stable yellow-fruited plants because you end up with a homozygous recessive for both yellow flesh and clear epi (yyrr).In the case of white-to-pink you would have to do a normal grow out to eliminate any possibility of heterozygous dominants (Rr) showing up in future generations. I don't think the plant from bejustice is a somatic mutation but, assuming it was: the pink fruit from such a somatic mutation is either yyRr or yyRR - most likely yyRr. Assuming self-pollination, expect a grow out of the pink fruit to present a genotype of 1/4 yyRR, 1/2 yyRr, and 1/4 yyrr, or a phenotype of 3/4 pink and 1/4 white fruit.

In plants, cells destined to become gametes do arise from somatic tissues. Plants, unlike animals, do not have a germ line. The fact that meristem organization is very flexible (contain a large number of undifferentiated cells) can allow accumulation of somatic mutations; most of the somatic mutations are not immediately life-threatening. There is genetic evidence that the developmental program of somatic and zygotic embryos is indistinguishable. The article Chris referenced above addresses this concept.

Anyway, in this particular case, with the weakened plant showing up along with the change in fruit color, it sounds like the mutation may have affected more than one gene and "messed up a whole chunk of the chromosome". If the initial grow out of, say 50(?), plants from the pink-fruited seed produces any white-fruited plants then I think the student would be better served to start from scratch and cross the white cherry with a robust pink cherry, then select for the desired traits. In this case it should only require one additional generation of grow outs and would also provide the student with more of an education.

Scott, our bottom line advice to bejustice is the same

- the seeds from the pink fruit have to be grown out and evaluated - stability can not be assumed.

Steve

August 14, 2013	#16
Heritage Tomatovillian™ Join Date: Nov 2010 Location: San Diego Posts: 1,255	Scott, you are correct about the possibility of the pink fruit not being stable. I had my previous red-to-yellow example on the brain when I said the pink fruit would produce all stable/pink fruit. In the case of a red-to-yellow somatic mutation all of the yellow fruit will produce stable yellow-fruited plants because you end up with a homozygous recessive for both yellow flesh and clear epi (yyrr).In the case of white-to-pink you would have to do a normal grow out to eliminate any possibility of heterozygous dominants (Rr) showing up in future generations. I don't think the plant from bejustice is a somatic mutation but, assuming it was: the pink fruit from such a somatic mutation is either yyRr or yyRR - most likely yyRr. Assuming self-pollination, expect a grow out of the pink fruit to present a genotype of 1/4 yyRR, 1/2 yyRr, and 1/4 yyrr, or a phenotype of 3/4 pink and 1/4 white fruit. In plants, cells destined to become gametes do arise from somatic tissues. Plants, unlike animals, do not have a germ line. The fact that meristem organization is very flexible (contain a large number of undifferentiated cells) can allow accumulation of somatic mutations; most of the somatic mutations are not immediately life-threatening. There is genetic evidence that the developmental program of somatic and zygotic embryos is indistinguishable. The article Chris referenced above addresses this concept. Anyway, in this particular case, with the weakened plant showing up along with the change in fruit color, it sounds like the mutation may have affected more than one gene and "messed up a whole chunk of the chromosome". If the initial grow out of, say 50(?), plants from the pink-fruited seed produces any white-fruited plants then I think the student would be better served to start from scratch and cross the white cherry with a robust pink cherry, then select for the desired traits. In this case it should only require one additional generation of grow outs and would also provide the student with more of an education. Scott, our bottom line advice to bejustice is the same - the seeds from the pink fruit have to be grown out and evaluated - stability can not be assumed. Steve Last edited by Heritage; August 14, 2013 at 09:21 PM.