Mendelism / by R.C. Punnett.

  • Punnett, Reginald Crundall, 1875-1967.
Date:
1912
Catalogue details

Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: Mendelism / by R.C. Punnett. Source: Wellcome Collection.

    113/218 (page 83)
    REPULSION AND COUPLING 83 has been known to occur in such a family. More¬ over, further breeding shows that while the erect reds and the hooded purples always breed true, the erect purples in such families never breed true, but always behave like the original plant, giving the three forms again in the ratio i : 2 : i. Yet we know that there is no difficulty in getting purple bicolors to breed true from other families ; and we know also that hooded red sweet-peas exist in other strains, On the assumption that there exists a repulsion between the factors for erect standard and blue in a plant which is heterozygous for both, this peculiar case receives a simple explanation. The constitutions of the erect red and the hooded purple are EEbb and eeBB respectively, and that of the erect purple is EeBb. Now let us suppose that in such a zygote there exists a repulsion between E and B, such that when the plant forms gametes these two factors will not go into the same gamete. On this view it can only form two kinds of gametes, viz. Eb and еВ, and these, of course, will be formed in equal numbers. Such a plant on self-fertilisation must give the zygotic series EEbb -|- 2 EeBb -b eeBB, i.e. Painted Lady X Duke of Westminster (erect red) (hooded purple) Purple Invincible (erect purple) Painted Lady (I) Duke of Westminster