Chromosomal Fragile Sites: Molecular Test of the Delayed-replication Model
This extract was created in the absence of an abstract.
Excerpt
Variations in chromosomal morphology and stability have long attracted the attention of geneticists and cytologists. Such variations have proved useful in addressing significant biological questions (Sutton 1903; Creighton and McClintock 1931). One interesting morphological variation results from mutant or normal alleles that lead to failure of a specific chromosomal site to condense in mitotic chromosomes. Breakage of chromosomes occurs more frequently at these sites, leading to what are called “weak points” (Kaufmann 1939) and “fragile sites” (see Sutherland and Hecht 1985). Darlington and La Cour (1940) observed that poorly condensed sites also could be induced in chromosomes of several species of Trillium and other plants by cold temperature. They suggested that such sites are “under-charged with nucleic acid,” and that it would be useful to look for abnormalities in nucleic acid and in “timing and regularity of gene division” (Darlington and La Cour 1940). An inherited human disease, fragile X...
