The genetic structure ofTulipa
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1. The tetraploid tulip species have a lower chiasma frequency at meiosis than the diploids and triploids and fewer changes of partner at pachytene than the latter. Consequently although autotetraploid, they form few quadrivalents and are sexually fertile.
According to the distribution of chiasmata among the four chromosomes. This shows to which of the ten possible types of quadrivalent they belong. These types depend on the number of changes of partner at pachytene and on the symmetry, half-symmetry or asymmetry of the chiasma distributions per chromosome.
According to the co-orientation of the centromeres at the first metaphase of meiosis, whether convergent, linear or indifferent. The type of co-orientation depends upon the distances apart of the centromeres in the multivalent at the time metaphase begins. Co-orientation fails altogether when the centromeres are further apart than they can be in bivalents. These principles agree with the repulsion theory of orientation.
3. The inter- and intranuclear mean squares show no significant correlation of chiasma frequency in the diploids. A slightly positive correlation in the tetraploids and variable correlation in the triploids is presumably to be attributed to the number of changes of partner their chromosomes undergo and to variable external conditions.
KeywordsSide View Extra Chromosome Chiasma Frequency Chromosome Race Pachytene Nucleus
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- Crane, M. B. &Thomas, P. T. (1939). “Genetical studies in pears. I. The origin and behaviour of a new giant form.”J. Genet.37, 287–299.Google Scholar
- —— (1930). “Studies inPrunus. III.”J. Genet. 22, 65–93.Google Scholar
- —— (1931). “Meiosis in diploid and tetraploidPrimula sinensis.”J. Genet. 24, 65–96.Google Scholar
- —— (1935). “Internal mechanics of the chromosomes. I–III.”Proc. roy. Soc. B,118, 33–96.Google Scholar
- —— (1936a). “The analysis of chromosome movements. I.Podophyllum versipelle.”Cytologia, Tokyo,7, 242–7.Google Scholar
- —— (1936b). “The external mechanics of the chromosomes. I–IV.”Proc. roy. Soc. B,121, 264–319.Google Scholar
- —— (1936c). “Crossing-over and its mechanical relationships inChorthippus andStauroderus.”J. Genet. 33, 465–500.Google Scholar
- —— (1937).Recent Advances in Cytology, 2nd ed. London: Churchill.Google Scholar
- Darlington, C. D. &Mather, K. (1932). “The origin and behaviour of chiasmata. III. TriploidTulipa.”Cytologia, Tokyo,4, 1–15.Google Scholar
- Haldane, J. B. S. (1931). “The cytological basis of genetical interference.”Cytologia, Tokyo,3, 54–65.Google Scholar
- Klingstedt, H. (1937). “On some tetraploid spermatocytes inChrysochraon dispar (Orth.).”Mem. Soc. Fauna Flora Fenn.12, 194–209.Google Scholar
- Lawrence, W. J. C. (1931). “The genetics and cytology ofDahlia variabilis.”J. Genet.24, 257–306.Google Scholar
- Levan, A. (1933). “Cytological studies inAllium. III.”Hereditas, Lund,18, 101–14.Google Scholar
- —— (1936). “Cytological studies inAllium. III.”Hereditas, Lund,18, 101–14.Google Scholar
- —— (1937). “Cytological studies in theAllium paniculatum group.”Hereditas, Lund,23, 317–70.Google Scholar
- -- (1939). “Competition for chiasmata in diploid and trisomic maize.”Chromosoma,1 (in the Press).Google Scholar
- Moffett, A. A. (1932). “Studies in the formation of multinuclear giant pollen grains inKniphofia.”J. Genet.25, 315–37.Google Scholar
- —— (1936). “The origin and behaviour of chiasmata. XIII. Diploid and tetraploidCulex pipiens.”Cytologia, Tokyo,7, 184–97.Google Scholar
- Müntzing, A. (1936). “The evolutionary significance of autopolyploidy.”Hereditas, Lund,21, 263–378.Google Scholar
- Newton, W. C. F. (1927). “Chromosome studies inTulipa and some related genera.”J. linn. Soc. (Bot.),47, 339–54.Google Scholar
- Newton, W. C. F. &Darlington, C. D. (1929). “Meiosis in polyploids. I.”J. Genet.21, 1–16.Google Scholar
- Shimotomai, N. (1933). “Zur Karyogenetik der Gattung Chrysanthemum.”J. Sci. Hiroshima Univ. B,2, 1–100.Google Scholar
- —— (1937b). “The external mechanics of the chromosomes. VI. The behaviour of the centromere at meiosis.”Proc. roy. Soc. B,124, 336–61.Google Scholar