| aspermatogenic sterility | Sterility due to a failure to produce living spermatozoa. (05 Mar 2000) |
|---|---|
| male sterility | The inability of the male to fertilise the ovum; it may or may not be associated with impotence. (05 Mar 2000) |
| hybrid sterility | <genetics, zoology> The inability of a hybrid to produce viable offspring. Whether an animal hybrid is sterile or fertile depends mainly on how closely its two parent species are related. For example: mules (which are hybrids between male donkeys and female horses) are usually sterile, while hybrids between domestic dogs and wolves are fertile (hybrids between wolves and foxes are also fertile, but hybrids between dogs and foxes are sterile). (09 Oct 1997) |
| sterility | 1. The inability to produce offspring, i.e., the inability to conceive (female sterility) or to induce conception (male sterility). 2. The state of being aseptic or free from microorganisms. Origin: L. Sterilitas (13 Nov 1997) |
| normospermatogenic sterility | Male sterility due to some cause other than failure to produce live, normal spermatozoa, e.g., blockage of the seminiferous passages. (05 Mar 2000) |
| dysspermatogenic sterility | Male sterility due to some abnormality in production of spermatozoa. (05 Mar 2000) |
| female sterility | The inability of the female to conceive, due to inadequacy in structure or function of the genital organs. Synonym: infecundity. (05 Mar 2000) |
| heterochromatin, facultative | Heterochromatin that need not always be heterochromatic but has the faculty to return to the normal euchromatic state. The inactive x chromosome is made up of facultatative heterochromatin. When a woman transmits that x to a son, it reverts to euchromatin and genetic activity. (12 Dec 1998) |
| facultative | Of parasites, optional. Compare: obligate. (09 Oct 1997) |
| facultative aerobe | <microbiology> An organism which is normally anaerobic but can also grow in the presence or oxygen. (15 Nov 1997) |
| facultative anaerobe | <microbiology> A microorganism which can survive without oxygen (is an anaerobe) but is not harmed if oxygen is present. (09 Oct 1997) |
| facultative heterochromatin | <cell biology> The heterochromatin which is condensed in some cells and not in others, presumably representing stable differences in the activity of genes in different cells. The best known example results from the random inactivation of one of the pair of X chromosomes in the cells of female mammals, (Lyonisation). (18 Nov 1997) |
| facultative hyperopia | Hyperopia that can be compensated by accommodation. Synonym: facultative hyperopia. (05 Mar 2000) |
| facultative parasite | An organism that may either lead an independent existence or live as a parasite, in contrast to obligate parasite. (05 Mar 2000) |
| facultative ponds | Ponds having an aerobic zone on the top and an anaerobic zone on the bottom. (05 Dec 1998) |