Yu C W, Downey H M, Priest J H
Hum Genet. 1980 Feb;53(2):149-53. doi: 10.1007/BF00273486.
The finding of heteromorphisms in certain regions of human chromosomes is useful in chromosome identification, especially in the study of the origin of nondisjunction. Quantitation of heteromorphisms in the smaller human chromosomes is theoretically valuable but remains technically difficult. In this paper we evaluate two methods for quantitation of human chromosome 21--visual densitometric measurement of Q-banded 34-mm negatives. Thirteen parameters are defined for chromosome 21. We find three of them to show less variability between different measurements of the same cell and from cell to cell in the same individual: (1) the centromere index, defined as the ratio of length of the satellite, stalk, and short arm to the length of the satellite, stalk and short and long arms; (2) the ratio of length of the satellite to the length of the total heteromorphic region of the short arm; and (3) the ratio of the short arm intensity to the intensity of band q21. Another parameter, the ratio of satellite intensity to the intensity of band q21, is reproducible by visual measurement but not by densitometry. Based on these studies we conclude that densitometry is not necessarily better than visual quantitation of the heteromorphic region of chromosome 21.
在人类染色体某些区域发现异态性有助于染色体识别，尤其在研究不分离的起源方面。对人类较小染色体上的异态性进行定量在理论上具有重要价值，但在技术上仍存在困难。在本文中，我们评估了两种对人类21号染色体进行定量的方法——对Q带34毫米底片进行视觉密度测量。为21号染色体定义了13个参数。我们发现其中三个参数在对同一个细胞的不同测量之间以及同一个体的不同细胞之间显示出较小的变异性：（1）着丝粒指数，定义为卫星、柄和短臂的长度与卫星、柄、短臂和长臂的长度之比；（2）卫星长度与短臂总异态区域长度之比；（3）短臂强度与带q21强度之比。另一个参数，卫星强度与带q21强度之比，通过视觉测量可重复，但密度测量不可重复。基于这些研究，我们得出结论，密度测量不一定比21号染色体异态区域的视觉定量更好。
