• F. A. E. Crew

      Articles written in Journal of Genetics

    • Sex-reversal in frogs and toads. A review of the recorded cases of abnormality of the reproductive system and an account of a breeding experiment

      F. A. E. Crew

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    • The inheritance of horns in the goat

      S. A. Asdell F. A. E. Crew

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      An examination of the Herd Book of the British Goat Society and of privately kept herd records provided strong support for the contention that, as in cattle, the polled and the horned conditions in the goat constitute a Mendelian pair of characters, polled being dominant. The data were too meagre to warrant any attempt to interpret the significance of scurs. Attention is called to the interesting fact that in this matter of horn inheritance the goat apparently resembles the ox rather than the sheep.

    • A case of lateral asymmetry in the domestic fowl

      F. A. E. Crew

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      A fowl with the left side of the body larger than the right is described. It is shown that, though the size difference is similar to that distinguishing male and female this bird was most probably not a gynandromorph.

      The lateral asymmetry is explained on the assumption that an autosome carrying white had been eliminated during the early cleavage divisions of a male zygote heterozygous for the characters white and yellow epidermal pigmentation.

    • A sex-linked recessive “lethal” inDrosophila obscura

      F. A. E. Crew Rowena Lamy

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      The mutation “white eye” is reported to have occurred once again inDrosophila obscura.

      A sex-linked recessive lethal, designatedl4, is located on theX-chromosome ofDrosophila obscura at 1.9 units of distance from the locus of Pointed.

    • A case of leg-colour asymmetry in the fowl

      F. A. E. Crew

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      AnF1 hen out of the sex-linked mating Light Sussex ♀ × Rhode Island Red ♂ had legs of different colours, the right showing the dominant white, the left the allelomorphic recessive yellow. It is suggested that this regional expression of a recessive in a heterozygote is due to the loss of a part of an autosome during the second cleavage division.

      Six other somewhat similar cases previously recorded and described as instances of either non-disjunction or gene mutation are discussed. The suggestion is hazarded that all of them can be regarded as examples of the loss of a whole autosome or of a part thereof.

    • A case of conditioned dominance inDrosophila obscura

      F. A. E. Crew Rowena Lamy

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      An autosomal recessive eye colour purple inD. obscura is described. The mutant is similar to purple inD. melanogaster but is peculiar in that it acts as a dominant diluter of vermilion. The double recessive vermilion purple is white. The time interaction of the two genes is disussed with reference to the process of pigmentation.

      It is suggested that the modes of interaction of these two genes, vermilion and purple, may be explained on the assumption that they are similar in nature and in function, and hence behave as allelomorphs.

    • The sex incidence of chiasma frequency and genetical crossing-over in the mouse

      F. A. E. Crew P. Ch. Koller

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    • Waved: An autosomal recessive coat form character in the mouse

      F. A. E. Crew

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      The mutant coat form character “waved” is an autosomal monogenic recessive.

    • A lethal in the rat

      F. A. E. Crew S. K. Kon

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      The existence of a monogenic autosomal recessive lethal in the rat is demonstrated. Death occurs, apparently from inanition, during the second week of lactation.

    • The second linkage group inDrosophila pseudo-obscura

      F. A. E. Crew Rowena Lamy

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      Three purple allelomorphs ofDrosophila pseudo-obscura Race A and their interaction with vermilion are described. Purple gives 47·2 per cent. recombination with Lancefield’s orange, and Scute, a new autosomal dominant, is shown to lie midway between purple and orange. The presence of an inversion in this chromosome is indicated.

    • Linkage groups inDrosophila pseudo-obscura. - With notes on homology and the nature of genic action

      F. A. E. Crew Rowena Lamy

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      1. Snapt, tilt and sepia are three genes on the left arm of theX-chromosome. On the right are eosin, an allelomorph of white, and cuprous, an allele of yellow.

      2. Stubble, a dominant, and glass form the nucleus of the 3rd linkage group, and short4 and jaunty that of the 4th. Tangled, it is thought, belongs to the 5th.

      3. It is suggested that: (i) a portion of the left arm of the 3rd chromosome ofD. melanogaster is homologous in part or in whole with the 3rd autosome ofD. pseudo-obscura; (ii) the right arm ofmelanogaster 3rd is in part homologous with the left arm ofpseudo-obscura X, and (iii) the right arm ofmelanogaster 2nd is in part homologous withpseudo-obscura 4th.

      4. It is suggested that the apparently disproportionate effect of some genes affecting eye colour is in reality cumulative.

    • Autosomal colour mosaics in the budgerigar

      F. A. E. Crew Rowena Lamy

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      1. Seventeen autosomal colour mosaics in the budgerigar (Melopsittacus undulatus) are described: sixteen of these being “half-siders.” It is suggested that every one of them is the result of the elimination of the “blue” autosome.

      2. The chromosome number is 50–60. There are three size classes: theX-chromosome is large: only oneX is present in the female. The very considerable number of small dot-like chromosomes makes it impossible to determine with certainty the actual number, and also to recognise chromosome loss. The large chromosomes show lagging.

    • The “plexus” chromosome ofDrosophila pseudo-obscura race A

      F. A. E. Crew Rowena Lamy

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      The character Plexus is described and shown to be based not on a single gene but on the inverted order of some of the genes in theX-chromosome. The resultant alteration in crossing-over is discussed.

      A series of mosaics arising in the Plexus stock is described and the origin and nature of the condition discussed.

    • A repetition oe modougall’s lamarckian experiment

      F. A. E. Crew

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      In order to be in a position to examine the conclusions which McDougall has reached, 18 generations of rats have been trained. The figures provided by 1445 experimentais and 1014 controls are compared with those which McDougall derived from 21 generations of rats of the same origin.

      Criticism is levelled at the methods adopted by McDougall for presenting his figures, and especially at his lack of adequate control.

      In the case of my rats the average number of errors per rat made by individuals of the tank-trained stock has not decreased with the passing of the generations, and there is no difference whatsoever between the scores of the experimental and control stocks. I have encountered no evidence which would suggest that rats of the trained and control stocks respectively can be distinguished one from the other by differences in behaviour. This being so I cannot accept the results which McDougall obtained as being in themselves strong enough to carry the interpretation that he has placed upon them.

      Analysis of my own pedigrees shows definitely that genetic factors are heavily concerned in the establishment of the scores. Two main classes of rats are involved, quick and slow, and in a general way quickness behaves as a dominant, slowness as a recessive. The parent-offspring correlation is 0.3. A “quick” strain has been developed as the result of consistent favourable selection. To “fix” a slow strain has proved to be a much more difficult task. The reasons for this are discussed.

      I submit that there is no need to postulate, in explanation of the fact that the average scores of the earlier and later generations of McDougall’s rats differ, that some new quality has been acquired and is being transmitted, for the average score of a generation is determined by the proportion of quick and slow rats within it, and these proportions can, within limits, be prearranged.

      Among my rats there is a great excess of those which tend to leave the tank habitually by one route during the first phase of their training when the light is constant and equal on both sides of the tank and when the platforms are not alive. A considerable number of rats reacted to light as light in the second phase of their training when the light was alternating but the platforms were not alive. Actually 29 experimental and 10 control rats “learnt” without receiving a single shock.

      The relation of handedness and photophobia to the score is discussed.

      I do not propose to carry the main study further. The search for the genetic basis of handedness and of photophobia is being continued.

    • A fertile and phaenotypically normal triplo-X female ofDrosophila pseudoobscura (Race A)

      F. A. E. Crew Rowena Lamy

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      A triplo-X female ofDrosophila pseudo-obscura, wild-type in characterization and carrying two yellow and two singed genes in association with one wild-type allelomorph of each of these, proved to be fertile in mating. The phaenotypes among her offspring and the numerical proportion of these strongly suggested that her two ovaries differed one from the other in respect of theX-chromosome content.

    • Mosaicism inDrosophila Pseudo-Obscura

      F. A. E. Crew Rowena Lamy

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      Mosaics inDrosophila pseudo-obscura resulting from haploidy and from double-nuclear fertilization are described.

      Both types are found among the offspring of homozygous and of heterozygous Plexus females.

      The haploid areas, in all but one case, carried the paternal genome.

      The diploid areas of haplo-diploid mosaics having nearly always been female, must usually have been derived from the same male pro-nucleus as the haploid area. This indicates that in these cases the male pronucleus, in the first division after fertilization, has not yet united effectively with the female pro-nucleus. The latter either fails to divide at this division, or one of its daughter nuclei fails to become incorporated in a zygote nucleus and is eventually lost.

      Double fertilization is probably occasioned by failure of the two daughter cells resulting from the second maturation division to separate from each other.

    • Rex: A dominant autosomal monogenic coat texture character in the mouse

      F. A. E. Crew Ch. Auerbach

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      Rex, a new, viable and fertile autosomal dominant coat texture character in the mouse, is described. Though phaenotypically very similar indeed to if not identical with Caracul, it is shown to be genetically distinct therefrom. The two genes are on different autosomes. When its linkage relations have been established Rex will serve as a most useful marker for further genetical work with the mouse.

    • Linkage data on the Rex character in the house mouse

      F. A. E. Crew Ch. Auerbach

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    • Spontaneous inverted exchange betweenX andY inDrosophila melanogaster

      F. A. E. Crew Rowena Lamy

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      1. The case is reported of a chromosome termedscYL formed by rearrangement between theY-chromosome and anX containing thescS1 inversion. The rearranged chromosome has on one side of its centromere the whole of the long arm of the normalY and on the other side a small section invisible in mitotic stages, containing the left distal end of theX, with the scute gene and the normal alleles of genes to the left of it.

      2. If the breakage and reunion occurred by a process of crossing-over, the chromocentral regions ofX andY here involved must have been in inverted position in regard to each other or else adjacent instead of diagonally opposite ends of the conjugating chromosomes must in this case have become attached together.

      3. In its new position on theY-chromosome the scute gene has an expression similar to that on its old position on theX-chromosome. Moreover the position effect is of a mosaic nature in theY as in theX.

      4. When thescYL forms a duplication ofsc, the scute effect is reduced and theHw effect accentuated, the body colour is darkened and the homozygousscS1 female (usually sterile) is rendered fertile; bristles are longer and thicker, and general viability is increased. In non-scute flies thescYL adds bristles in the dorsocentral region, and gives a slightHw effect.

    • “Pigtail,” a hereditary tail abnormality in the house mouse,Mus musculus

      F. A. E. Crew Charlotte Auerbach

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      A skeletal abnormality, termed pigtail, in the house mouse is described which phenotypically resembles flexed tail. In a certain small proportion of litters, one or more young with spina bifida aperta occurred, especially in the more highly inbred litters. Genetically, pigtail is a recessive character, caused either by two complementary factors, or—more probably—by one main gene interacting with a number of modifiers which affect the penetration. Penetration is never 100%. In genetically pigtail litters, it varies round about 20%. It is not noticeably dependent on age of mother, degree of expression in the parents, degree of inbreeding or selection; but there exists a significant, though slight, negative correlation between litter-size and percentage of manifestation in homozygous litters, suggesting some intra-uterine, non-genetical influence on the development of the abnormality.

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