Craig J M, Bickmore W A
MRC Human Genetics Unit, Western General Hospital, Edinburgh.
Bioessays. 1993 May;15(5):349-54. doi: 10.1002/bies.950150510.
The mammalian chromosome is longitudinally heterogeneous in structure and function and this is the basis for the specific banding patterns produced by various chromosome staining techniques. The two most frequently used techniques are G, or Giemsa banding and R, or reverse banding. Each type of stained band is characterised by variations in gene density, time of replication, base composition, density of repeat sequences, and chromatin packaging. It is increasingly apparent that R and G bands, which are complementary to each other, represent separate compartments of the euchromatic human genome, with R bands containing the vast majority of genes. R bands are also more GC-rich, contain a higher density of Alu repeats, and replicate earlier in S phase, than G bands. These properties may be interdependent and may have coevolved.
哺乳动物的染色体在结构和功能上存在纵向异质性，这是各种染色体染色技术产生特定带型的基础。两种最常用的技术是G（吉姆萨带型）或R（反带型）。每种染色带的特征在于基因密度、复制时间、碱基组成、重复序列密度和染色质包装的变化。越来越明显的是，相互互补的R带和G带代表了常染色质人类基因组的不同区域，其中R带包含绝大多数基因。与G带相比，R带也富含GC，含有更高密度的Alu重复序列，并且在S期更早复制。这些特性可能相互依赖，并且可能共同进化。
