• C. H. Waddington

      Articles written in Journal of Genetics

    • Pollen germination in stocks and the possibility of applying a lethal factor hypothesis to the interpretation of their breeding

      C. H. Waddington

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      Tests have been carried out of the germination on artificial media of the pollen of double-throwing races (d. races) and pure breeding single races (no-d. races) of Stocks (Matthiola incana M. Br.). The percentage of germination obtained in the no-d. races ranged from 76 to 29, and that in the d. races from 29 to 1.5. The difference is statistically significant.

      The evidence of the germination tests can, perhaps, be accepted as sufficient to show that a difference exists between the pollen of the d. and no-d. races in respect to the possibility of germination. If this is so, theories which attempt to explain the genetical behaviour of Stocks in terms of pre-maturation segregation lose their main support.

      Rival theories, such as those which postulate gametic lethals, must therefore be considered. A theory of this type is brought forward, which is claimed to account for the facts better than previous similar theories: but it does not fit the facts any better than does Saunders’ scheme, which, however, does not account for the lack of certain classes of gametes.

      It is shown that the hypothesis brought forward in this paper provides a plausible explanation of the breeding results which have been obtained by Frost, working with the trisomic race Slender.

    • The genetic control of wing development inDrosophila

      C. H. Waddington

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    • The development of some ‘leg genes’ inDrosophila

      C. H. Waddington

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    • The structure and development of four mutant eyes inDrosophila

      C. H. Waddington R. W. Pilkington

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      1. The structure and development of four types of mutant eyes inDrosophila melanogaster has been investigated.

      2. Infacet the secondary pigment cells are enlarged, and this causes an irregular constriction of the cone-cups and bulging of the facets.

      3. Inlozenge-spectacled the cells of the middle layer fail to penetrate between the cells of the outer layer in early pupal life, and later the retinulae fail to penetrate the basal layer.

      4. Inophthalmopedia the eye-forming portion of the optic disk in the late larva may be enlarged, and abnormally folded; the folded portion later gives rise not to ommatidia but to a palp of body-surface chitin bearing bristles.

      5. The structure and development of themorula eye appears to be identical with that previously described forsplit, except that the cone secretion is normal.

    • A note on some alleles of aristapedia

      C. H. Waddington R. Clayton

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      Larvae homozygous for several alleles of aristapedia (ssa, ssaB, ssa40a andssaSnB) were transferred for three days to 18°C. after being kept at 27°C. for 12,24,36,48 or 60 hr. from laying. They were then scored for the grade of transformation of the arista into a tarsus and for the distortion of the normal tarsus. In all cases both the abnormalities were increased by cold treatments given after 48 or 60 hr.

      The patterns of effect were similar inssa40a andssaSnB, both of which always have a strong aristal effect and in the higher grades a strong tarsal effect;ssaSnB is always stronger thanssa40a under the same conditions.

      A different pattern is characteristic ofssa, which has a strong aristal effect and a weak tarsal effect. The pattern is different again inssaB, which at high temperature has a weak effect, and at low temperature a moderate effect, on both aristae and tarsi.

      The existence of these different patterns of effect shows that the alleles are not related in a simple quantitative manner, but differ qualitatively.

      In flies homozygous for alleles which have strong effects on both organs (i.e.ssa40a andssaSnB) the aristal tarsus may be stunted just as is the leg tarsus. This demonstrates that the effect of the gene is not produced by a simple growth stimulation.

    • The interactions of some morphogenetic genes inDrosophila melanogaster

      C. H. Waddington

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      Flies have been bred which were homozygous for each of two or more of certain genes which have strong morphological effects. The loci concerned were ssa, pb, bx, vg, blt, Xa, ap4, cg, fj, ds, rn.

      The interactions between genes which were expressed in the double homozygotes are described and discussed. It is suggested that stronger interaction may be expected between genes which act simultaneously on the same developmental system than between those which act successively. The former class are described as ‘homodynamic’.

      It is shown that certain genes, which usually appear to have narrowly localized activity, exhibit a considerably more general influence when in combination with other morphogenetic genes, and the bearing of this fact on the theory of the localization of gene action is discussed.

      In certain strains of bithorax and vestigial, the failure of one mesothoracic bud to evert has led to regulatory development in the mesothoracic bud of the opposite side or the metathoracic bud of the same side. This is taken to indicate that the determination of the form and chaetotaxy of the thoracic rudiments is not complete until after eversion, that is to say, some time after puparium formation.

      The genes comb-gap (second chromosome) and cubitus interruptus (fourth chromosome) are ‘ pseudo-allelic’, since the double heterozygote cg/ + ci + shows the characteristic break in the fourth longitudinal wing-vein.

    • The genetic basis of the ‘Assimilated Bithorax’ stock

      C. H. Waddington

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      The phenotype of the ‘assimilated bithorax’ stock is due in part to a number of genes, on all the chromosomes, which act directly on the individuals containing them. and partly to a recessive X-chromosome condition which causes a maternal effect.

      Attempts to break down the maternal-effect condition by crossing-over were unsuccessful.

      The maternal effect condition, when made homozygous in a wild-type background, causes the appearance of some bithoraxes in the next generation.

      The condition may have arisen by mutation during the course of the selection by which the assimilated stock was built up, but it may have been present in very low frequency in the initial population.

      The offspring of females homozygous for the maternal-effect condition do not produce a higher percentage of bithoraxes, following ether treatment, than do flies of similar genotype from other mothers.

    • ISO-Alleles and the response to selection - With one text-figure

      C. H. Waddington H. Graber B. Woolf

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      A IVth chromosome containing the semi-dominant alleleciw was introduced into a strain, the rest of the genotype being that of an inbred Canton wild type. Selection was practised for the degree of expression of the heterozygote. Response to the selection occurred. It was found that after some forty generations the response had not involved the production of any new iso-alleles at theci locus. If other loci behave in the same way the mutation rate to iso-alleles cannot be great enough for the mutations of any one locus to play an important role in response to selection.

    • The genetic basis of the ‘Assimilated bithorax’ stock

      C. H. Waddington

      More Details Abstract Fulltext PDF

      The phenotype of the ‘assimilated bithorax’ stock is due in part to a number of genes, on all the chromosomes, which act directly on the individuals containing them, and partly to a recessive X-chromosome condition which causes a maternal effect.

      Attempts to break down the maternal-effect condition by crossing-over were unsuccessful.

      The maternal effect condition, when made homozygous in a wild-type background, causes the appearance of some bithoraxes in the next generation.

      The condition may have arisen by mutation during the course of the selection by which the assimilated stock was built up, but it may have been present in very low frequency in the initial population.

      The offspring of females homozygous for the maternal-effect condition do not produce a higher percentage of bithoraxes, following ether treatment, than do flies of similar genotype from other mothers.

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