Showing papers in "Journal of Genetics in 1928"

The experimental formation of heteroploid plants in the genussolanum

Abstract: 11. iM I,Trnoi)s 135 A. The Format ion o[ Halfloid l?hmts 135 17;. The Format ion of Polyploid P lan t s 150\" I lL MoltrHot,oov or,\" Tin,' 1-[l,:rrt,mor~,OrD ,SO[,A~-O~IS 156 A. '.['ho eomparat,ive morphology of diploid, triploid and tel, rt~ploid tomatoes 157 B. The, eomp'l.ra, tive morphology of ha.ploid, diploid, grip|old and tetr+Lploid ,S'. niffrum, . Ill0 C. The, compa.rativo morphology of S. niWivm, S. htleu m, S. +nil~rum x l'uleu.m diploid and tetn~ploid l(i.l IV. (JY'I'OLO~:Y OF 'rKl~l HETI'~IIOPr, OID 8o[, ,x . .xtf~ts . 1 6 9 A. ']Jim comparat.ivo cyt,ology of diploid, t, riploid and tetraploid tontatoes . [(i9 B. The cytology of ha.ploid, dilfloid, triploid and totraploid S. ~dgrum 174 C. The cytology of N. niflrum, S. h+t.e+tm and S. uiffrum, x 1.to.m, diploid and tctraploid , 185

The estimation of linkage from the offspring of selfed heterozygotes

Abstract: Five methods of solution are given of the statistical problem presented by typical linkage data. The example chosen shows the various errors into which the use of inefficient statistics leads. Of the efficient methods the method of maximum likelihood possesses the advantage that it may be applied directly to any analogous problem, and is related in a previously unsuspected way to the measure of discrepancyX 2. The product ratio method, for using which a table is provided, enjoys the practical advantages of other efficient solutions, and is in addition unaffected by differential viability, if this is caused by one factor only. The method of minimumX 2, unlike the other two, is laborious in computation, and seems to possess no special theoretical interest.

Sexual difference of linkage inGammarus chevreuxi

Abstract: InGammarus chevreuxi there is a marked sexual difference in linkage intensity. For the factors B-G, the mean cross-over value for females is 50.4 per cent. on 2133 specimens, for males is 25.4 per cent. on 4154 specimens. It is impossible at present to decide whether the state of affairs in the female is due to true linkage with high c.o.v., or to independent chromosomes which undergo pseudo-linkage in the male; though the former is the more probable. There is great variation in linkage intensity in both sexes; but the shape of the frequency polygons obtained is different for the two sexes. The variation appears to be due in large part to genetic causes. The fact that absence or marked reduction of crossing-over in the autosomes of one sex has only so far been recorded for the heterogametic sex is mentioned and its theoretical bearings discussed.

Hybrids ofDigitalis ambigua andDigitalis purpurea, their fertility and cytology

Abstract: A number of hybrids between.Digitalis purpurea ♀ andD. ambigua ♂ were obtained. Two plants among the hybrids showed a low degree of fertility. From the others no seeds were obtained. TheF 2 generation differed from theF 1 principally in size, but there was no segregation of the parental characters. About 75 per cent. were highly fertile. The chromosome numbers of the parent species and of theF 1 hybrid are 28 (n) and 56 (2n) in each case. In theF 2 hybrid (artificial pollination) the numbers are 56–112, while all plants obtained from open pollination of theF 1 are triploid (84-2n) and sterile. The viable spores of theF 1 result from the failure of the reduction division and the formation of restitution nuclei. Digitalis purpurea ×ambigua is an additional example of a constant intermediate hybrid resulting from chromosome doubling.

The agouti coloration of the Mouse (Mus musculus) and the rat (Mus norvegicus)

Abstract: IN a recent paper I oll the coat of the Mouse mention was made of preliminary observations on the agouti co]our pattern. I t is now desired to record certain details of pigmentation in the wild type of the Mouse and the gag which lend support go the conclusions of Onslow and Wright as to wherein lies the difference between agouti and non-agouti. The features of hair growth and form dealt with in the other paper need not now be recapitulated, and few new terms will be employed. Attention may be directed especially to the section on hair-type-associations within single follicles, and also to the plates, ileferences are eibed in the previous paper. The skins used were from captured animals with the exception of the mouse skins in which the third or later pelages were examined. Those were from black agouti stock obtMned ~rom a f~neier, and the same applies to the living rats used for observations on hair succession. The work has been confined almost entirely to mice that had not grown more than the first three hair generations, and to rats bearing only the first and second pelaggs. The points brought out depend upon the existence of differences rather than the extent of those differences, and it is not deemed necessary to present tables of measurements. Where the conformation of the body is the same no difference between the sexes has been detected in any hair character. The description of pigmentation in the Mouse would be largely applicable to the Rat, but the details have been studied more thoroughly in the smaller animM. In the lla~ measttrements of hairs have been made only for the region of \"the mid-dorsam. T ~ MousE.

Amputated, a recessive lethal in cattle; with a discussion on the bearing of lethal factors on the principles of live stock breeding

Abstract: CONTENTS. PAGE I. IN~'~OD'UC'~ION 187 ~. DESOgIPTION O]P TI-I]~ At~IPU'f~kTED O.dLVES 188 3. HEREDIT'm~Y '9~rPE OF T~E ~FOR~I~TION . 193 ~:. C~ININllAL OONSIDERATION8 AND DISOUSSIOi~ . ~0][ (a) The influence of the gre~t sires in live stock breeding 201 (b) The occurrence and spreading of recessive leghMs in live stock 205 (e) The econonficM importance of recessive lefihMs in c~ttle. '209 (d) PracgicM measures for prevention of the spreading of lethMs 211

Notes on species crosses in primula, godetia, nemophila , and phacelia

Abstract: CONTENTS. PAt-t l] PRIMULA Hybrids within ~he Vernales section 285 Clm.raetm's of types and hybrids 287 Pin and thrum 291) Flower colon r 290 ]-I aMncss 292 Pedmmle 292 Eye colour 293 Other characters 293 Table of results 291 (-]ODET'IA Ma,terial used 294 Amocm~Whit~,e.yi section . 296 Ta.bte of results 297 Bollac.tenella.lcpida sectiml 301 Table of results 300 ~r EMOPIIILA M,M~eria.1 used 304 N. linziflora 305 N. atomaria . 307 N. iT~sign.is 310 I')IIA 6'EL l.'i Material used 310 Table of results 312

Rye-Wheat hybrids from reciprocal crosses

Abstract: 1. Crosses between wheat and rye present no special difficulties if wheat is used as the mother plant. The percentage of successful fertilisations depends in this case chiefly on the choice of the races intended for crossing purposes. 2. Reciprocal crosses, where the pistillate parent is rye, were until quite recently considered impossible. We succeeded, however, in making such crosses when the flowers of local winter rye were pollinated with the pollen of the pure line wheat No. 648, which readily hybridises with rye in direct crosses. 3. In 1925, when the technique of these crosses had been sufficiently elaborated, we obtained 96 grains from 3894 rye flowers emasculated and pollinated with wheat pollen,i.e. 2.5 per cent. of successful fertilisations, while in direct crosses this percentage usually exceeds 60. 4. F1 plants from direct and reciprocal crosses proved to be identical in morphological characters, as well as in fertility. 5. Maternal inheritance recorded by E. F. Gaines and F. J. Stevenson for reciprocal crosses—rye ♀ x wheat ♂—has not been confirmed by our experiments.

Inheritance inLolium perenne L.

Abstract: 1. A vigorous, full greenLolium perenne plant gave rise on selfing to three distinct types of seedlings: surviving green, non-surviving green and chlorophyll-deficient (yellow-tipped albino). The number of seedlings so obtained, owing to high self-sterility, was insufficient to show anything beyond the occurrence of these types and that the plant was heterozygous for at least two pairs of factors. This plant is known as plant 43. 2. The non-surviving green seedlings die back just before or just after the appearance of the second leaf. 3. The yellow-tipped albino seedlings may survive for some months, but they never closely approach a full green colour and never become sufficiently strong for use as parents. 4. When the original plant was out-crossed to unrelated plants, neither non-surviving green nor yellow-tipped albino seedlings were obtained inF 1. 5. WhenF 1 plants were back-crossed to the original parent, the three types of seedlings again appeared and in such proportions as to indicate that in respect of two pairs of factors, the constitution of plant 43 may be represented by the symbolsLlYy. 6. Amongst theF 1 seedlings, the typesLlYy,LLYy and —YYYY were found by selfing, back-crossing and side-crossing. 7. There is no indication of linkage between the two factorsL andY.

Inheritance of structural types in the dorsosacrum of domestic poultry

Abstract: I. Introduct ion 29 II . .Description of the pelvic types . 30 III. I l lustrations of the heredRary nature of the characters studied . 37 IV. Inheri tance of pehdc types with four and five dorsosacral vertebrae . 38 V. HeredRary modifications of the pelvis with four dorsosacrM vertebrae 44 Vl. Inheri tance of the pelvic type with three dorsosacrM vertebrae -.t6 VII. Concludh:g remarks 48 VIII. Summary . 50

The development of the leaves in certain periclinally variegated plants

Abstract: Arabis albida variegata, Euonymus japonica aurea andE. japonica argentea are periclinally variegated plants. They possess a subepidermis which is distinct from the inner tissue at the apex of the shoot and forms a layer of cells one cell thick, except for slight irregularities, over most of the leaf but thicker at the margins. From its development it seems likely that the subepidermis may form the white “skin” which causes the characteristic appearance of these periclinally variegated plants. The sectorially variegated dicotyledonVeronica gentianoides variegata and the sectorially variegated monocotyledonChlorophytum have a growing point in which the greater part of the stem apex and the young leaves are formed directly from division of subepidermal cells. It would be impossible for the subepidermis to form a white “skin” over the plant in these cases.

Colour inheritance in sheep III. Face and leg colour

Abstract: 1. A type of pigmentation in sheep is found in which the derivatives of the primitive outer coat-face and leg hair, kemp, and birth-coat-are coloured and the body of the fleece practically free from colour. 2. Variations in face colour fall into three groups: (1) Those affecting the relative proportions and distributions of coloured, and white fibres. (2) Those affecting the dilution of this pigment. (3) Those affecting the precise degree of restriction of pigmentation in the white-faced sheep; this pigment being mainly confined to the skin. 3. A further analysis of the results of T. B. Wood in his crosses of Suffolk and Dorset Horn sheep shows that these results can be explained on the basis of a two-factor difference, the variations in this case being of group 1. 4. As a working hypothesis, it is suggested that the above classification, together with the recognition that variations of group 1 are mainly due to the different states of two factors, affords a reasonable explanation of the variations in face colour found in the white-fleeced breeds of sheep and in their crosses.

Further studies on inheritance inMatthiola incana. II. Plastid colour and doubling

Abstract: AT an earlier s~age in the investigation 1, as recalled in the last contribution dealing with inheritance in Matthiola ~, it was suggested that it might be possible to syn~hesise a double-throwing (eversporting) strain of Stocks from a non-double-throwing (true-breeding) single if the breeding was carried out in a certain specified way. For if an eversporting single be crossed with pollen from a non-double-throwing single we know that the resulting F 1 singles will be of two kinds, (1) those which yield both singles and doubles in F2, and (2) those which produce only singles. If for this mating an individual of a d. sulpkm'-whifie 3 strain is used as ? and a form in which all the pollen carries single cream as •, the known heterozygous constitution of the mother plant and the uniform clmracter of the pollen of the male parent enable us, without h~rther breeding tests, by simple inspection of the plastid colour, to make a preliminary selection of F 1 individuals to be used in the next step. This will be obvious on reference to the factorial combinations involved in this tmion set forth on p. 54 in which W = the factor for white (coloarless) plastids, and X and Y = the two factors requisite for singleness, X ~ being linked with W in the eversporting, and with Y in the true-breeding single.

A case of lateral asymmetry in the domestic fowl

Abstract: 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.

Genetic studies inRicinus communis L.

Abstract: The work recorded in this paper has resulted in the identification of a number of factors inRicinus affecting the colour of the vegetative parts, the leaf bloom, the colour and pattern of the seed coats, leaf laciniation, spines, and albinism. The colour of the vegetative parts is dependent upon the presence or absence of three factors,M,G, andE, the last of which is here noticed for the first time. The various types of leaf bloom are shown to depend upon the action of three separate factors,B,C, andD. The colour of the seed coat is dependent upon two factors,P andA. The pattern is affected by a factor,W, and there is some evidence suggesting that it may be further influenced by two other complementary factors. It is also shown that the pattern is influenced by one of the factors affecting the colour of the vegetative parts, viz.G. For leaf laciniation, spines, and albinism a single factor has in each case been demonstrated, differentiating them from the normal form. An interesting point in connection withRicinus is that, for the various characters worked with, partial dominance is the rule. Apart fromM andB, already known to be linked, no case of linkage was found among such combinations as were made between the various factors investigated.

Bateson’s experiments on bolting in sugar beet and mangolds

Abstract: The ordinary stocks of the cultivated varieties ofBeta maritima— mangolds, sugar beet and garden beet—constitute mixed populations mainly biennial in habit but containing a certain small proportion of individuals which will “bolt” under ordinary conditions of sowing in the open. This proportion rises rapidly under conditions favourable to bolting,e.g. early sowing, a check to growth. Sowing under glass at the beginning of the year and transplantation into the open about April will induce upwards of 70 per cent. of the seedlings to bolt. Selection of seed for two or three generations from plants which do not bolt under such forcing conditions gives rise to strains of seed from which the bolting tendency has been so far eliminated that none will bolt under ordinary conditions of sowing in the open or even when “forced.” Though “bolting” is markedly affected by environment, by conditions of nutrition, temperature, etc. to which the plant is subjected, the individuals differ in their proneness to bolt, or in the resistance they offer to conditions that encourage bolting. These differences are shown to be genetic in origin and are inherited. Thus while the ordinary mixed stocks contain individuals which will bolt without any special stimulus and others which will not bolt even under the most forcing conditions practicable, it is possible to extract a race consisting only of the latter, which might be termed a pure biennial race. The evidence suggests that high resistance to bolting as compared with low resistance is not a simple character, but it is insufficient for the framing of a definite factorial scheme.