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Linkage groups and chromosome number in Lathyrus

1927; Royal Society; Volume: 102; Issue: 716 Linguagem: Inglês

10.1098/rspb.1927.0054

2053-9185

R. C. Punnett,

Chromosomal and Genetic Variations

After the discovery of linkage of characters in the sweet pea, the question naturally arose as to a possible connection between these linked groups and the chromosomes. It was realised that a definite contribution would be made to such an inquiry if it could be decided whether the groups showing linkage, together with characters exhibiting independent assortment, were more numerous than the haploid number of the chromosomes, or not. With the advent of several fresh and easily worked characters, a definite series of experiments with this object in view was started in 1908, and since that time the work has gradually been extended as further favourable characters were met with. While it was in progress the question at issue was definitely decided in the case of the little fruit fly, Drosophila melanogaster . The rapidity and ease with which this material could be bred placed it beyond a doubt that the number of linkage groups is here the same as the haploid number of the chromosomes, viz., 4. Hitherto, however, Drosophila has in this respect remained unique. Of recent years a considerable amount of work has been done in connection with linkage groups in plants, notably in Pisum, Antirrhinum , maize, wheat and barley, but in no case is progress yet sufficient to allow of a categorical statement; and, indeed, there would appear to be an inclination on the part of some workers, notably among those with Pisum , to recognise a number of linkage groups and independently assorting characters greater than the haploid number of the chromosomes. For Lathyrus , however, the first species in which investigations of this nature were planned and begun, a definite answer has at last been obtained.