Showing papers in "Journal of Genetics in 1932"

A method for investigating recessive characters in man

Abstract: A method is given by which, the true proportion of recessives may be calculated from human or other data on small families.

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

Abstract: THE many studies of the chromosomes of the mouse have been concerned mainly with theb number or with the sex-chromosome constitution. Tafani, as early as 1889, had given 20 as the haploid number, whilst Sobotta (1895) found 16, and Gerlach (1906) 12. With improvements in cytological techniques, Long (1908), and more recently Painter (1926, 1927, 1928) and Cox (].926), have been able ~o show conclusively that the number is 20 in the haploid state and that in this form male heterogamety exists. The investigation now to be described deals with the chromosome behaviour during mitosis and meiosis. It is an application and extension of the results obtained by Janssens, Belling, Briar and Darllngton, using other material, and was dbected particularly to an examination of the partial chiasmatype hypothesis as enunciated by Janssens (1909-2~1) and modified by Darlingtou (1931, 1932 b).

Studies on the creeper fowl: III. The early development and lethal expression of homozygous creeper embryos

Abstract: I~ an earlier report we have offered genetic proof that the gene determining the typical features of the Creeper variety of fowls is lethal when present in homozygous condition (Landauer and Dunn, 1930). We have stated ah'eady in that report that the typioal lethal period of homozyg'o~s Ch'eeper embryos is to be found at the beginning of the fourth day of incubation, and that at this stage the homozygous embryos appear to be considerably smaller and less well differentiated than normal ones. We have also stated that under favourable conditions some of the homozygous Creeper embryos survive the critical period at the beginning of the fom%h day, and that such embryos later exhibit mm~hological features resembling phokomelia. Our present report is concerned with a more detailed description of those homozygous Creeper embryos .which die at the beginning of the fom%h day of incubation. The phokomdia-like homozygous Creeper embryos will be discussed in a Nture report.

Studies on the formation of multinuclear giant pollen grains inKniphofia

Abstract: DURING the autumn of i980, a preliminary cytological examination was made of several species and varieties of Ifni~hofia. It was found that the basic (haploid) chromosome number was 6 and that chromosome pairing and separation at meiosis was for the most part perfectly regular. In some of the preparations examined, however, pollen mother cells were observed in which 12 or 24 chromosomes were scattered at random throughout the cell. Du~ing the present season, 1931, fm'ther investigations have been made, and in some flowers abnormally large multinuclear pollen grains were observed. At the pollen grain divisions it was fmmd that these giant pollen grains were diploid or tetraploid with 12 or 24 chromosomes. The investigations were continued with a view to determining how these abnormal pollen grains were formed, and the results are embodied in this paper.

Chromosome variation inCrocus. I

Abstract: The somatic chromosome complements of sixty-four species and varieties ofCrocus were examined, and a comparison of them shows that the chromosomal variation in the genus results from: (i) Hybridisation and polyploidy. (ii) Fragmentation and possibly fusion. (iii) Genotypic change controlling bulk and width of the chromosomes.

The genetics of cotton

Abstract: 1. A series of six multiple allelomorphs controlling the distribution of anthocyanin pigmentation has been demonstrated in Asiatic cottons. The symbols,R, R1, Rc, Rs, ro, andrg are proposed for them. 2. Red, the highest member of the series, has been shown to be dependent for its full expression on the presence ofY, the gene for yellow corolla. 3. The presence in theR chromosome of genes affecting lint length and seed weight, has been demonstrated. These genes have been shown to be responsible for only a small proportion of the variations observed in lint length and seed weight. 4. The bearing of the distribution of anthocyanin genes and their modifiers on the classification of the cultivated Asiatic cottons has been discussed, and conclusions similar to those drawn in previous papers (Hutchinson, 1931, 1932a) have been arrived at. 5. TheR series of multiple allelomorphs has been found to segregate independently of theY series, and ofA, one of the two complementary genes for “crumpled.”

A cytological study of the genusSorghum pers

Abstract: In “diploid”Sorghum species, 2n = 20, 10 bivalents are usually found, but quadrivalents and sexivalents occur occasionally.

Genetic and cytological studies ofMusa

Abstract: 1. Artificial pollination of the sterile and parthenocarpic Gros Michel banana (somatic chromosome number 33) by a fertileMusa, identified as a variety ofM. malaccensis Ridl. (somatic chromosome number 22), results in formation of occasional seeds, the average seed production being less than one per hundred flowers. 2. Of ten plants raised from such seeds and examined cytologically, eight have 44 somatic chromosomes and two about 75. The former resemble their female parent, and have parthenocarpic fruits but an increased pollen fertility; the latter are thick-leaved, dwarf, and apparently sterile. 3. Of five plants, forming anF2 generation from one of the 44-chromosomeF1 individuals, three have 44 somatic chromosomes, and two have 46. 4. TheF1 crosses back to its female parent only with extreme difficulty, but crosses readily with its male parent, giving vigorous progeny with 33 somatic chromosomes. 5. The course of events suggests that the basic haploid chromosome number in this series is eleven. The meiotic phenomena are not inconsistent with that hypothesis, but they further suggest that the eleven is a secondary haploid number, possibly derived from an original eight.

The genetics of cotton: Part VII. “Crumpled”: A new dominant in Asiatic cottons produced by complementary factors

Abstract: Summary1.Two complementary factors,A andB, causing abnormal development have been demonstrated in Asiatic cottons.2.A has been found in two strains ofG. Nanking var.soudanensis obtained from the Sudan.3.B has been found in seventeen varieties ofG. arboreum, G. Nanking, G. herbaceum andG. obtusifolium, and in a strain ofG. Stocksii from Sind.4.The existence of a number of modifying factors affecting the degree of expression of the “crumpled” character has been demonstrated.5.It was not possible to correlate eitherA orB with any character in normal plants.6.Examination of sections from near the growing point of a “crumpled” seedling revealed no marked abnormalities.

The genetic analysis of familial traits: II. Double gene substitutions, with special reference to hereditary dwarfism

Abstract: Summary1.The limits between which the expected ratios of affected offspring of parents of all possible phenotypes will lie, when a trait is determined by two complementary dominant genes on different chromosomes, or two independent recessive genes, have been investigated in this communication. The proportions expected vary with the incidence of the trait in the population. In the case of a trait determined by two independent complementary dominant genes the limiting value for matings of two normal parents is the same as that for a single recessive trait. When the two gene frequencies are of the same order this limit is reached rapidly.2.Recorded data of various pathological conditions have been examined from this standpoint, and it has been shown that the extant observations on ateleiosis, and the Japanese cases of hereditary optic atrophy are interpretable on the assumption that this condition is significantly determined by two dominant genes. It is unlikely that this explanation will be found to apply to achondroplasia. It is possible that it applies to cleft palate, harelip and glioma retinae.3.The foregoing analysis emphasises four prerequisites for the application of factorial analysis to clinical data. These are: first, exact information concerning the frequency of familial traits in the general population; second, the elimination of any bias due to neglect of families with a low familial incidence; third, the collection of random samples of matings involving one affected parent unbiassed by the possibility that such matings may or may not yield affected offspring; and finally, searching enquiry into the tendency to assortative mating.4.One significant outcome of the present enquiry is the fact that the expected proportions of affected individuals calculated in such a way as to make allowance for the small size of the human family diverge at the lower limit much less rapidly than is at all obvious at first sight, as the number of genes determining a given trait increases.

A cytological study of the genus Sorghum Pers.

Abstract: The somatic chromosome number of Johnson Grass,S. halepense, is 40. The wild sorghums,S. virgatum, S. verticilliflorum, S. vogelianum, S. lanceolatum, S. arundinaceum, the cultivated grass,S. sudanense, and the grainSorghum “species,”S. guineense var.involutum, S. caudatum,S. papyrescens, S. Cafforum, andS. Cafforum vars.subglabrescens andmelaleucum, S. cernuum, S. Roxburghii var.hians, S. Durra, and six other varieties of these species which are not yet officially named, all have 20 chromosomes. A number of tetraploid segments and one octoploid segment were found in root tips of diploid plants. In one tetraploid cell the chromosomes were closely paired. One peculiar-shaped chromosome can be identified in all the species examined. It is present only in duplicate in the tetraploidS. halepense.

On the interaction of heredity and environment in the study of human genetics (with special reference to Mongolian imbecility)

Abstract: The effect of environment in the study of human genetics has been discussed, especially in relation to the observation of numerical ratios of affected persons to normal where the inheritance, not of a disease, but of the susceptibility to a disease is under consideration.

Further studies inTradescantia virginiana var.humilis andRhoeo discolor

Abstract: 1. InTradescantia virginiana var.humilis the following observations were made on meiosis: (i) arrest of terminalisation of chiasmata (ii) pairing of unequal chromosomes (iii) torsion of chromatids (iv) morphological change in chromosome (v) pairing of fragments, discussed in relation to the chiasma theory of metaphase pairing. 2. InRhoeo discolor pachytene, diplotene and diakinesis stages were observed. The metaphase end-to-end pairing of the chromosomes was observed to follow earlier side-by-side pairing of homologous ends.

Further studies of linkage in the sweet pea

Abstract: Extensive data are given on the crossing of eighteen pairs of characters inLathyrus odoratus. As a result these eighteen pairs arrange themselves.into five linkage groups and two unassociated characters. Since the haploid number of the chromosomes is seven, the data are in accordance with the chromosome theory. Attention is drawn to the frequency of deficiency of recessive characters in theF 2 generation, and it is suggested that the degree of deficiency may possibly be correlated with the age of the recessive mutation in question, the youngest mutations showing the most marked deficiencies, andvice versa.

Step-allelomorphism and the theory of centres of the gene, achaete-scute

Abstract: Tmn theory of eentres of the gene has been explore([ by Dubinin, Serebrovsky, and other authors in s~udying the ach.a, ete-scute gene in Drosophila mdanoyaster. The principles.bring at the foundation of ~his consist in admitting the divisibility of the gene into elementary units which have been termed een~res. Ea, eh transgenation a, rising within the aeha, ete-scute basigene represents a certain eombina,tion of some of the twelve een%res, which together constitute the basigene. The map ot2 t.he ba,sigene is fmmd.ed on a.n orderly eonabina:gio~ of cetltres occurriug dl~rlng f, ra,nsgenation. The basigene ma.p proved to be [iacar (Dubinin, 1,930) (Fig. 1). In Fig. 1 the map of the achaete--scu~e ba, sigeae is given.

The genetic analysis of familial traits: III. Matings involving one parent exhibiting a trait determined by a single recessive gene substitution with special reference to sex-linked conditions

Abstract: VII. Summary1.The present communication discusses the quantitative analysis of matings involving one affected parent, when a clinical condition is determined by a single recessive gene substitution.2.The proportion of matings showing direct transmission is higher than would be calculated from the theory of random mating. One reason for this is that the application of a theory of random mating is limited by the geographical propinquity of the individuals concerned. There must, therefore, be a limit of dilution beyond which increasing rarity of the trait does not appreciably decrease the probability that an affected individual will mate with a carrier.3.Matings of albinos with normal individuals having affected offspring satisfy the hypothesis that albinism is determined by a single recessive autosomal gene substitution. The discrepancy for matings of two normal parents with some albino offspring is not significant for large families, and may hence be attributed to biased selection of the small families recorded.4.There are very few exceptions to the rule that all types of matings in stocks displaying red-green colour blindness conform to the requirements of the hypothesis that the condition is determined by a single recessive gene substitution on theX-chromosome.5.As far as the extant evidence can be regarded as trustworthy, haemophilia must be interpreted as a recessive sex-linked condition which is alsosex limited.6.There are two forms of Leber’s disease, both genetical types being found among Europeans and probably both among Japanese, though the majority of examples of the recessive sex-linked form are European and the majority of the Japanese cases are of the type which is apparently determined by two autosomal dominant genes.

Phalaris arundinacea, Ph. tuberosa, theirF1 hybrids and hybrid derivatives

Abstract: CONTENTS. P A G E Ini~roduction 1 Secl}ion I. ]3reeding 2 1. T_hc p~reng species . 2 2. Inigi~l breeding: methods and results 4 3. Morphology of the F 1 hybrids . 5 ~. Male-fertility in t)11c Fj. hybrids 9 5. l~emalc-fcrtili~y in the /~'1 hybrids 9 6. The second generagion l l 7. The ~lfird generation I4 8. The fourth generation 15 9. Discussion on Sect~ion I 16 10. Summ~ry of Section I 20 Section I I . Clu:omosome studies \" 21 1. The somatic complement 22 2. The gtmlctic complement 23 3. Discussion on Section I I , 27 ~. Summ~ry of Section I I 29 Section I I I , General discussion . 30

The effect of short ultra-violet rays on the appearance of hereditary variations inDrosophila melanogaster

Abstract: UmmL quite recently (]%0), ~he qsmstion a,s '~o ~ho inflnenc'e of the ultra-violet .t'ays on the mu'gadon process has remained unanswered, or has been answered b. a negative sense. Th.e negative conclrtsions were on. the one kand based on tl:morcticat considerations as to din ]dnd of action possessed by the ultra-vio].eb rays such as the:it wave--length which is 9.2000 times greater "than that of l~oen~gen and radimn rays, their strong absorption, etc. ; and on the other hand on the negative results obtained from genetieal experiments (64uyenot, 1914; Altenburg, 1928). While Altenburg's first experiments (lee. tit 0 ted him to negative conclusions, they suggested at the same time ~he need of grea~aer precision in the physical method of experimenting. ]Later he made, in 19,30, a second brief communication staging that he had obtained a lethal effect from the ultra-violet rays (lee. eit.). He concluded that they influence the frequency of the appearance of lethal mutations in D~'oso~)hila m&~notaster, but in a far lesser degree, than ltoentgen or y-radium rays. No data on influence of ultra-violet rays on the appearance of visible hereditary variations in Drosol)hila melanoga, ster have, to my knowledge, as yet been published, and the interest of the present work lies in the fact ~ahat it has brought to light some peculiar phenomena in the phenotypical and hereditary variability of this species.

The chromosomes of the domestic chicken

Abstract: (1) The diploid number in the chicken is 66 plus or minus two. (2) The haploid number is 33 plus or minus one. (3) There is a very great difference in size between the largest and the smallest chromosomes with every gradation in between. (4) The largest pair of chromosomes in the male is represented by a single element in the female. These are regarded as sex-chromosomes. (5) No sign of aW-chromosome was observed.

Studies on the Creeper fowl: V. The linkage of the genes for Creeper and single-comb

Abstract: ConclusionsLinkage tests were made between the genes for single-comb and for the Creeper condition in fowl. Four geographically different lines or Creeper chickens were used in the matings. Chickens which were heterozygous for Creeper and rose-comb were crossed to others which were homozygous for the two recessive genes (normal skeleton and single-comb). Both heterozygous males and females were used in these back-crosses. The experiments extended over the first and second laying year. The total progeny of these matings amounted to 6627 individuals.The results show that linkage between the genes for Creeper and single-comb is very close, the frequency of crossing-over in the whole material amounting to 0·36 per cent. The data suggest that crossing-over occurs more frequently in females (0·57 per cent.) than in males (0·13 per cent.). No definite relation could be established between age and crossing-over. The Creeper characters of all four lines which were used for the crosses appear to be due to an identical mutation.On the basis of our present knowledge it seems likely that the Creeper condition is caused by a section deficiency of the chromosomes in which the comb allelomorphs are located.

Genetics of the primroseP. Acaulis

Abstract: A pure white primrose which does not turn yellow in ammonia vapour, and therefore contains no flavones, has been taken as the basis of the investigation. The ordinary hue of the red primrose is a magenta red. If the colour is superimposed on a yellow primrose, the magenta has a more yellowish appearance than if it is superimposed on an ordinary white flower from which the yellow has been eliminated. If, however, the colour is superimposed on a pure white flower, it is no longer magenta, but a bright carmine hue, without any of the bluish tinge of the ordinary magenta primrose. There appears to be one anthocyanin present, which can be readily transferred to a yellow, ivory white or pure white background respectively.

Genetical evidence for a cytological abnormality in man

Abstract: Evidence is adduced from pedigrees that certain women are of constitution Open image in new window , the twoX-chromosomes being attached.