User:Balapagos/sandbox

'''Research accomplishments

Lilian was the original discoverer of the attached-X and ring-X chromosomes in Drosophila melanogaster (1922, 1933). The normal Drosophila X-chromosome is telocentric, i.e. the centromere is located on one end of the chromosome. Attached-X (or A-X) is produced when two X-chromosomes share one centromere. Such an event produces a compound reversed metacentric chromosome - notation C(1)RM, that is transmitted as a single entity. Briefly, she isolated a female genetic mosaic fly which had a yellow coloured abdomen. This female gave birth to daughters that surprisingly exhibited the recessive X-linked trait (yellow body) and sterile sons that were otherwise normal in appearance. Further crosses using the F1 progeny supported the notion that the mosaic female's father's X-chromosome was a "double-yellow". The C(1)RM, y strain has been invaluable for Drosophila genetics. It allows us to stably maintain X-linked mutant alleles in males (that contain a single-X-chromosome and a Y-chromosome) amidst fertile A-X females (that can also host the Y-chromosome).

The discovery of the ring-X chromosome, notation R(1)1, by Lilian originated from an observation that sometimes the progeny of A-X yellow females (after mating with a y+ male) can give rise to wild type daughters. This indicated that one of the A-X must have detached itself. Such detached X-chromosomes exhibited unexpected genetic ratios and low recombination rates of distantly located markers. Furthermore, Lilian observed that in females that were homozygous for the detached-X the frequency of gynandromorphs was noticeably higher. Cytological examination through chromosomal preparations revealed a circularized X-chromosome. The unstable nature of ring-X (and their sensitivity to ionizing radiation) has been applied by many to generate XX and XO cells during mitosis to generate mosaic tissues containing recessive loss-of-function alleles of specific X-linked genes.