In contrast, female embryos contain measurable levels of Xist mRNA starting at the late 2-cell stage and rapidly accumulate Xist transcripts until morula stage. Xist levels per embryo then plateau abruptly, while cell division continues. Yet another ongoing project in the laboratory involves topological mapping of structures within the nuclei of neutrophils, the most common type of white blood cell. Human neutrophil nuclei typically consist of a linear array of three or four lobes joined by DNA-containing filaments. Terminal lobes at the ends of the string are necessarily connected via a single filament, while each internal lobe has two filaments.
Some lobes also have appendages of various shapes and sizes.
Similarly, the active-X chromosome is also randomly distributed among terminal and internal lobes. In addition, the drumstick itself exhibits characteristic spatial features and certain chromosomes preferentially stain filaments. These findings are currently being pursued using laser technology to dissect individual nuclei. In Human Neutrophil Nuclei. Submitted to Chromosoma.