Sex Chromosomes. Sex chromosomes are particular chromosomes that are involved in determining the sex of an organism. In the cells of humans and many other organisms the sex chromosomes consist of a pair of chromosomes called the X and Y chromosomes. The X and Y chromosomes were first discovered in beetles by Nettie Stevens in 1906.
What makes up household dust: 1  Dead skin cells. 2  Live dust mites. 3  Dead dust mites and dust mite feces.  Pollen and 1  allergens. Combustion byproducts (smoke)  Clothing 1  fibers. Pesticide residue.
Dust Hazard Analysis. A Dust Hazard Analysis or DHA is a process hazard analysis focusing on combustible dust. The DHA provides a formal document to determine where hazards exists, what safeguards are in place, and what safeguards are needed. The DHA process is now a requirement in many of the NFPA combustible dust standards including NFPA 652.