Colbert D A, Edwards K, Coleman J R
Differentiation. 1976 Jun 4;5(2-3):91-6. doi: 10.1111/j.1432-0436.1976.tb00897.x.
DNA from the chicken genome was analysed both by isopycnic centrifugation in cesium salt density gradients and by reassociation analysis using hydroxyapatite (HAP) chromatography. Centrifugation in neutral CsCl revealed a single non-Gaussian band skewed toward the heavy side, but no discrete satellite components. In heavy metal (Ag+ or Hg++)-Cs2SO4 gradients, 4-8 satellite bands were revealed, comprising 5-9% of the total DNA. Purification of the satellites and recentrifugation in neutral CsCl demonstrated that 80-90% of this DNA would band in the shoulder, with the remainder in the main band. These satellites can account at most for 30% of the heavy shoulder DNA, thus most of the heavy shoulder DNA must be of lower repetition frequencies. Reassociation analyses of chicken DNA demonstrated that the complexity of the non-repetitive DNA is 9.49 X 10(8) nucleotide pairs, equivalent to about 90% of the haploid genome. Repetitive DNA comprises only 8-10% of the genome and has the following composition, relative to total DNA: 3.7% intermediate repetitive, 1.9% highly repetitive, and 3.9% "zero-time binding" DNA. This unusually low repetitive DNA content may be related to the small genome size of chickens, relative to other vertebrates, and to the presence of many microchromosomes in the chicken karyotype. Total cell RNA extracted from perfusion myoblasts, post-fusion myotubes, and myoblasts grown in BrdU was incubated in large excess with 3H-TdR labelled non-repetitive DNA and the resulting hybrids assayed by HAP chromatography. The amount of non-repetitive DNA represented in the RNA was found to increase from 7-8% in the myoblast stage to 10-11% in myotubes. An even smaller proportion, about 5%, is represented in the RNA of myoblasts prevented from differentiating by growth in BrdU.
利用铯盐密度梯度等密度离心法以及使用羟基磷灰石（HAP）色谱的重退火分析，对鸡基因组的DNA进行了分析。在中性CsCl中离心显示出一条偏向重侧的单一非高斯带，但没有离散的卫星成分。在重金属（Ag+或Hg++）-Cs2SO4梯度中，发现了4-8条卫星带，占总DNA的5-9%。对卫星进行纯化并在中性CsCl中再次离心表明，这种DNA的80-90%会在肩部形成条带，其余部分在主带中。这些卫星最多可占重肩部DNA的30%，因此大部分重肩部DNA的重复频率必然较低。鸡DNA的重退火分析表明，非重复DNA的复杂度为9.49×10⁸个核苷酸对，约相当于单倍体基因组的90%。重复DNA仅占基因组的8-10%，其组成如下，相对于总DNA：3.7%为中等重复，1.9%为高度重复，3.9%为“零时间结合”DNA。这种异常低的重复DNA含量可能与鸡相对于其他脊椎动物较小的基因组大小以及鸡核型中存在许多微小染色体有关。从灌注的成肌细胞、融合后的肌管以及在BrdU中生长的成肌细胞中提取的总细胞RNA，与大量过量的3H-TdR标记的非重复DNA一起孵育，然后通过HAP色谱法检测产生的杂交体。发现RNA中代表的非重复DNA量从成肌细胞阶段的7-8%增加到肌管中的10-11%。在BrdU中生长而阻止分化的成肌细胞的RNA中，代表的比例甚至更小，约为5%。
