The morphologic characteristics of chromosomes are best studied during metaphase and anaphase of cell division. The chromosome was supposed to be covered by a membranous Pellicle. Electron microscope studies later showed that there is no definite membranous pellicle surrounding the chromosomes. A matrix of some sort, possibly protein, lipid, may be present. Other structures present in the chromosome include the [...]
The following points highlight the top two models of chromosomes. The models are: 1. Multiple Strand Models 2. Single Strand Models. Model # 1. Multiple Strand Models: a) Simple Multi-Stranded Model: According to this model the chromosome consists of 64 double helices of DNA arranged in a parallel number, and twisted together like the strands of a rope. The difficulty [...]
The following points highlight the eight main criticisms for Lyon’s hypothesis. Criticism # 1. That XO, XXX, XY, XX etc. individual differ among themselves suggesting that the entire X chromosome is not genetically inactive. If it were so, an XX and XXX female would have had no difference at all. From various chemical stigmata it seems that a part of [...]