"Chromosomal puffs" refer to localized puffiness or swelling that can be observed in certain regions of chromosomes under a microscope during specific stages of the cell cycle, particularly in problemase I of meiosis. These puffs correspond to areas of increased genetic activity where RNA transcription is actively taking place. They are also known as "chromomeres" and are believed to contain clusters of genes that are being transcribed. The puffed regions can vary in size and number, and their appearance is thought to be related to the regulation of gene expression during development and differentiation.