profaz

Profaz, also known as prophase, is the first stage of mitosis in eukaryotic cells. During profaz, chromatin condenses into discrete, visible chromosomes, each consisting of two sister chromatids held together at the centromere. The nucleolus disappears as transcriptional activity declines, signaling the transition from chromatin to condensed chromosomes. The mitotic spindle begins to form outside the nucleus as centrosomes or other microtubule-organizing centers move toward opposite poles. Microtubules and other spindle components organize into a bipolar apparatus, with astral microtubules extending toward the cell cortex.

As profaz progresses, the nuclear envelope starts to break down, allowing spindle fibers to interact with chromosomes. By the end of profaz, the nuclear envelope is largely disassembled, the spindle apparatus is fully formed, and the chromosomes are oriented for subsequent capture and alignment. The events of profaz set the stage for prometaphase and metaphase, where microtubules attach to kinetochores and chromosomes begin to align along the cell’s equator.

The precise timing and mechanics of profaz can vary among organisms, particularly between animal and plant cells. In all cases, profaz serves to compact genetic material and establish the structural framework for accurate chromosome segregation during cell division.