A dominant gene will always be expressed when present, such as in the homozygous dominant genotype (RR), or heterozygous genotype (Rr). A recessive allele is only expressed wh â¦ en the genotype is homozygous recessive (rr).
(Lung alveoli, in contrast, are lined by very thin simple squamous epithelium .). Pseudostratified respiratory epithelium consists primarily of columnar ciliated cells. Ciliary beating sweeps mucus and the dust it carries up the bronchi and trachea toward the pharynx, where it can be swallowed.
This section of pseudostratified columnar epithelium is from the mucosal lining of the trachea has a ciliated surface. Notice the classic layering of the nuclei within the epithelium that give it the stratified appearance. What appears stratified is, however, a single layer.