Since DNA is particularly dense in sperm-forming cells, such cells may be especially susceptible to UO2++-derived damage.
Two genes involved in the function of the cilia basal body, outer dense fiber of sperm tails 2 (ODF2) and ezrin (EZR), were significantly downregulated in smokers as compared to nonsmokers (p<0.005 for both).
Furthermore, the single generative-like cell nuclei of fbl17 mutant pollen is distinctively larger and less dense than the sperm cell nuclei observed in wild type pollen at anthesis (Figure 2D) and its morphology is reminiscent of the generative cell nuclei before the second mitotic division.
The most common sequences were derived from genes that are known to be highly expressed in the testis in other organisms and include heat shock protein 90A [ 20], chitobiase [ 21], outer dense fiber of sperm tails [ 22] and kinectin [ 23].
And dolphins, too, and on the floor, raised on something like bed legs, is a stuffed basking shark and, in a corner, the skull of a sperm whale – dense, complex convolutions of bone.
Once a lineage has small spores, this may facilitate its transition to separate sexes because female thalli producing more numerous spores create a denser spore shadow, permitting sperm to more easily reach thalli of the opposite sex.
If small spores are cheaper to produce than large ones they can be produced in larger numbers, which might be especially advantageous in dioicous species for which a dense spore shadow and dense population of gametophytes might provide reproductive assurance (because sperm would not have to swim far).
Tektin2 and Tektin4 are microtubule- or outer dense fiber-associated proteins in sperm flagella [ 32, 33].
Sperm competition may be high when synchronous spawning occurs in dense aggregations [ 31, 32], but intensity of sperm competition (as a function of sperm density), and therefore sexual selection, may vary over small spatial and temporal scales with changes in population density.
