. Cell heredity. Cytogenetics. 96 Normal CELL HEREDITY 9 il 2 3 4 sj 6 7 8 9 lo| 11 17 10 9 8 761 2345 11 Rearranged 9 o CX3 — 17 (a). 17 C^ Xl" -O-^S}-- (c) FIGURE Origin of dicentric chromosome in maize (after B. McClintock, 1941, Genetics, 26:234). (o). Comparison of chromosome 9 before and after rearrangement resulting from three X-ray-induced breaks denoted by arrows. Stippled circles represent knobs, clear circles represent centromeres, the dotted region 1-5 indicates position of cross- over, and the heavy lines represent heterochromatic regions. (fa). Pachytene pairing of norm
. Cell heredity. Cytogenetics. 96 Normal CELL HEREDITY 9 il 2 3 4 sj 6 7 8 9 lo| 11 17 10 9 8 761 2345 11 Rearranged 9 o CX3 — 17 (a). 17 C^ Xl" -O-^S}-- (c) FIGURE Origin of dicentric chromosome in maize (after B. McClintock, 1941, Genetics, 26:234). (o). Comparison of chromosome 9 before and after rearrangement resulting from three X-ray-induced breaks denoted by arrows. Stippled circles represent knobs, clear circles represent centromeres, the dotted region 1-5 indicates position of cross- over, and the heavy lines represent heterochromatic regions. (fa). Pachytene pairing of normal 9 with rearranged 9 showing point-to-point pairing configuration, and the position of crossover which gave rise to the dicentric chromosome shown in (c). (c). Dicentric chromosome resulting from the crossover shown in (fa). CHROMOSOME BREAKAGE AND REARRANGEMENTS Judging from the similarities in chromosome morphology and in genetic linkage from strain to strain of most species, one might infer that the chromosome is an exceedingly stable structure. It came as something of a surprise, therefore, when geneticists found that chromo- somes were readily able to undergo breakage and rearrangement. De-. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Sager, Ruth; Ryan, Francis J. (Francis Joseph), 1916-. New York, Wiley
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