• D. G. Catcheside

      Articles written in Journal of Genetics

    • Gamolysis of various new Oenotheras

      R. Ruggles Gates D. G. Catcheside

      More Details Fulltext PDF
    • Chromosome catenation in someF1Oenothera hybrids

      D. G. Catcheside

      More Details Abstract Fulltext PDF

      The chromosome linkages in a number ofOenothera F1 hybrids have been found to show that (1) the chiasma frequency per pair of chromosome limbs is higher in the bivalents than in the multiple rings, (2) the pairs of frequencies in different hybrids are positively correlated, and (3) breaks (chiasma failures) occur at random in the rings.

      Evidence of interference between chiasmata is also brought forward and discussed. It appears likely that short chromosomes have a higher mean frequency relative to their length than have longer chromosomes.

    • The nature of closedX-chromosomes inDrosophila melanogaster

      Jack Schultz D. G. Catcheside

      More Details Abstract Fulltext PDF

      The two closedX-chromosomes ofDrosophila melanogaster, that originated as single individuals from mothers carrying attachedX-chromosomes, are shown to be duplicated at their bobbed, deficient at their yellow ends. This is in agreement with their origin as the result of translocations between the attachedX’s carried by their mothers.

    • The effect of x-ray dosage upon the frequency of induced structural changes in the chromosomes ofDrosophila melanogaster

      D. G. Catcheside

      More Details Abstract Fulltext PDF

      The frequency of induced structural changes of chromosomes observed inF1 female larvae ofDrosophila melanogaster raised from X-rayed males shows a direct linear proportionality with the X-ray dosage between 1000 and 4000 r.u. The relation of this fact to the “breakage” and “contact” hypotheses of their induction is discussed. Both hypotheses theoretically require sigmoid curves (with different characteristics) connecting dosage and effect. At intermediate doses the relation would be approximately linear on both hypotheses. The observations therefore do not provide any basis for discrimination.

      The high frequency (11%) of rearrangements, which on the contact hypothesis would require three or more threads in contact at one point, makes it unlikely that the chromosomes are ever in contact before, during or after irradiation unless they completely fill the treated nucleus.

      The high frequency of inversions in one chromosome arm, relative to interchanges between different arms, demonstrates a spatial preference either in the refusion of breakage ends or in a grouping of original breaks through a contact or analogous mechanism.

    • The bearing of the frequencies of x-ray induced interchanges in maize upon the mechanism of their induction

      D. G. Catcheside

      More Details Abstract Fulltext PDF

      A study of X-ray induced interchanges in maize has shown, in theF1 progeny from irradiated pollen, that individuals with two rings of four chromosomes are slightly more frequent than those with a ring of six chromosomes. Similar relations between these two classes hold at different X-ray doses. These facts may be accounted for on the contact hypothesis or on the breakage hypothesis if it be supposed that structural rearrangements chiefly follow breaks occurring in nearby positions. The data cannot be used to decide whether translocations require one or more hits for their production.

    • A position effect inOenothera

      D. G. Catcheside

      More Details Abstract Fulltext PDF

      In an X-ray induced interchange ofOenothera blandina, the capacity of the genePs for pigmenting the flower buds is reduced. One of the chromosome breaks is in arm 3 of chromosome 3.4, close to the locus ofPs. When the translocatedPs gene is transferred to normalblandina by crossing-over it reçovers its normal activity. This is the first experimental demonstration of a position effect in plants.

    • The mechanism of the induction by radiation of chromosome aberrations inTradescantia

      D. E. Lea D. G. Catcheside

      More Details Fulltext PDF
    • The effect of ionization distribution on chromosome breakage by X-rays

      D. G. Catcheside D. E. Lea

      More Details Abstract Fulltext PDF

      1. The coefficients of chromatid breakage (compare Table 4) are highest with AgL-radiation (λ=4·1 A.) and fall off through CuK-radiation (λ=1·5 A.) to medium X-rays (λ=0·15 A.) and to AlK-radiation (λ=8·3 A.) where they are least.

      2. This is interpreted to mean that only the densely ionizing ‘tails’ of the electron tracks are effective in chromosome breakage, and that the ‘tails’ have a higher efficiency only where they traverse the chromatid; for the track of an AlK-electron which is shorter than a chromatid diameter is relatively inefficient.

      3. The probability of survival of chromatid breaks is the same in the pollen-tube nucleus as in the pollen-grain nucleus.

      4. The two chromatids of a chromosome are in contact 24 hr. before metaphase in the pollen-grain nucleus. They are slightly separated 15 hr. before metaphase in the pollen-tube nucleus.

      5. The probability of interchange in the pollen-tube nucleus is reduced by the different method of packing of the chromosomes in a long cylindrical nucleus as compared with the spherical one of the pollen grain.

    • The rate of induction of dominant lethals inDrosophila melanogaster sperm by X-rays

      D. E. Lea D. G. Catcheside

      More Details Abstract Fulltext PDF

      The rate of X-ray induction of dominant lethals in the sperm of the Oregon-R stock ofDrosophila melanogaster is, at low doses, 12% per 1000 r. for death in the embryo stage, and 20% per 1000 r. for death at any stage between the zygote and the adult. At higher doses of X-rays both rates increase. Over the whole dose range, therefore, the doseaction curve does not fit a single-hit type of action, though this is approximated at low doses.

      The rate of depression of the sex ratio of females to males, founded on our own and other data, is about 2·5% per 1000 r.

    • The relation between recessive lethals, dominant lethals, and chromosome aberrations inDrosophila

      D. G. Catcheside D. E. Lea

      More Details Abstract Fulltext PDF

      The suggestion is put forward that radiation-induced recessive lethals, or a large proportion of them, are due to chromosome breaks. About one-third of all the chromosome breaks primarily induced by the radiation are lethals. If the break restitutes, a lethal unaccompanied by chromosomal aberration (type A lethal) results. If the break takes part in chromosome interchange a type C lethal, which is associated with chromosomal structural change, results. Arguments are given against the alternative position-effect explanation of type C lethals.

      A quantitative theory of dominant lethals is developed on the basis that the dominant lethals are a mixture of single breaks which fail either to restitute or to interchange but instead undergo sister-union, and of non-viable chromosomal structural changes involving two or more breaks. The experimental curve of variation with dose of the yield of dominant lethals is successfully fitted, and also the curve of the yield of viable structural changes.

      It is shown that the recessive lethal and the dominant lethal theories are consistent in that they require the same postulated number of primarily produced chromosome breaks per unit dose (namely, 0·75 breaks per sperm per 1000 r.). Experiments on the distortion of the sex ratio in the progeny of irradiated males with ring-shaped or rod-shapedX-chromosomes are also shown to be consistent with the theory.

    • Dominant lethals and chromosome breaks in ringX-chromosomes ofDrosophila melanogaster

      D. G. Catcheside D. E. Lea

      More Details Fulltext PDF
    • The bearing of radiation experiments on the size of the gene

      D. E. Lea D. G. Catcheside

      More Details Abstract Fulltext PDF

      At various times it has been proposed that the size of the gene can be estimated from experiments on the yield of mutations obtained with known doses of X-rays. The assumptions involved in calculations of this sort are discussed, and some of the objections which have been raised against them answered. It is pointed out that similar assumptions, applied to experiments on the inactivation of enzymes and viruses, lead to estimates of the sizes of these bodies correct to a factor of two in diameter. The estimate arrived at for the size of the gene inDrosophila is 4–8 mμ diameter. The length of the euchromatic region of theX-chromosome thread in the sperm is deduced to be 10–20 μ.

    • Types of chromosome structural change induced by the irradiation ofTradescantia microspores

      D. G. Catcheside D. E. Lea J. M. Thoday

      More Details Fulltext PDF
    • The production of chromosome structural changes inTradescantia microspores in relation to dosage, intensity and temperature

      D. G. Catcheside D. E. Lea J. M. Thoday

      More Details Fulltext PDF
    • TheP-locus position effect inOenothera

      D. G. Catcheside

      More Details Abstract Fulltext PDF

      InOenothera blandina, the genesPs,Pr andS produce a variegated phenotype when they are present in the interchange chromosome 3.11. When transferred by crossing-over to a normal 3.4 chromosome, they produce normal phenotypes. The variegation is therefore a position effect.

      The break is 1·7 units from theP locus and 8·5 units from theS locus, indicating a considerable spread of the position effect along the chromosome. The action is thought to depend on translocation of theP andS loci to the neighbourhood of heterochromatin.

      Theories of the mechanism of position effect are considered, but theOenothera case adds nothing new to the solution of the problem.

    • A duplication and a deficiency inOenothera

      D. G. Catcheside

      More Details Fulltext PDF
  • Journal of Genetics | News

    • Editorial Note on Continuous Article Publication

      Posted on July 25, 2019

      Click here for Editorial Note on CAP Mode

© 2021-2022 Indian Academy of Sciences, Bengaluru.