Gametes sentence example
Pollen must be strong to protect the male gametes on their journey.
The production of gametes, be they sperm in males or eggs in females, requires major changes in the mechanism of chromosome segregation.
An albino is a homozygote; that is, all its gametes are carrying the character of albinism and none of them bear the alternative character - the allelomorph - of pigmentation.
The same laws apply to the individual hyphae and their branches as to simple sporophores, and as long as the conidia, sporangia, gametes, &c., are borne on their external surfaces, it is quite consistent to speak of these as compound sporophores, &c., in the sense described, however complex they may become.
The diagrams below compare the formation of normal gametes and those formed by non-disjunction.Advertisement
Any debate now about the potential use of artificial gametes will have to be based on hypothetical scenarios.
It also plans to monitor the impact on treatment services with donor gametes in clinics around the country.
In 2005, the guidance was simplified to allow 10 families to be created from any one donor's gametes.
G Gametes - Mature reproductive cells, sperm or ova in humans produced by meiosis.
Gametes Reproductive cells which unite in pairs to produce zygotes.Advertisement
In reality, a number of studies suggest that sterile triploids are " leaky ", and some fertile gametes are sometimes produced.
It is possible, however, that the segregation of characters in the gametes may depend upon something far more subtle and elusive than the chromosomes or even of possible combinations of units within the chromosomes, but so far as we can see at present these are the only structures in the cell with which it can be satisfactorily associated.
The HFEA also regulates the storage of gametes (eggs and sperm) and embryos.
Fraternal twins are referred to as dizygotic twins, meaning that two unions of two gametes or male/female sex cells occurred to produce two separate embryos.
Identical twins represent the splitting of a single fertilized zygote (union of two gametes or male/female sex cells to produce a developing embryo) into two separate individuals.Advertisement
Gonads-Organs that produce gametes (eggs or sperm), i.e., the ovaries and testes.
Gonads-Organs that produce gametes (eggs or sperm), i.e. the ovaries and testes.
The male gametes, it may be noted, are said to possess the essential characters of a Trypanosome.
In this latter case the determinants for black are carried by separate gametes from those carrying grey, and the two kinds of sex-cells exist in approximately equal numbers.
Or, to express it otherwise, an albino extracted from yellow parents, bred with an albino extracted from black parents, will give an albino offspring whose gametes in equal numbers are bearers of the black and yellow determinants.Advertisement
Now such a gametic (egg or sperm) constitution can only result when two individuals, all or some of whose gametes are pure with regard to the character albinism, meet in fertilization.
Whether a spore results from the sexual union of two similar gametes (zygospore) or from the fertilization of an egg-cell by the protoplasm of a male organ (oospore); or is developed asexually as a motile (zoospore) or a quiescent body cut off from a hypha (conidium) or developed along its course (oidium or chlamydospore), or in its protoplasm (endospore), are matters of importance which have their uses in the classification and terminology of spores, though in many respects they are largely of academic interest.
The cytology of zygospore-formation is not known in detail; the so-called gametes which fuse are multinucleate and are no doubt of the nature of gametangia.
They have never been found to cause in fection, and they have not the characters of conidia; the large size of their nuclei, the reduction of their cytoplasm and the absence of reserve material and their thin cell wall all point to their being male gametes.
Thus among Volvocaceae, a family of Protococcales, while in some of the genera (Chloraster, Sphondylomorum) no sexual union has as yet been observed, in others (Pandorina, Chlorogonium, Stephanosphaera, Sphaerella) conjugation of similar gametes takes place, in others still (Phacotus, Eudorina, Volvox) the union is of the nature of fertilization.Advertisement
Thus, although isogamy consists in typical cases of a union of naked motile gametes by a fusion which begins at the beaked ends, and results in the formation of an immotile spherical zygote surrounded by a cell-wall, in Leptosira it is noticeable that the fusion begins at the blunt end; in a species of Chlamydomonas the two gametes are each included in a cell-wall before fusion; and in many cases the zygote retains for some time its motility with the double number of cilia.
In these cases the activity of one of the gametes, and the passivity of the other, is regarded as evidence of incipient sex.
In Zygogonium, although no cell-division takes place, the gametes consist of a portion only of the contents of a cell, and this is regularly the case in Mesocarpaceae, which occupy the highest grade among Conjugatae.
It would seem that in some cases the nuclei of the gametes remain distinct in the zygospore for a considerable time after conjugation.
Gametes which fail to conjugate sometimes assume the appearance of zygospores and germinate in due course.
The conjugation of similar gametes, arising from distinct plurilocular sporangia, was observed by Berthold in Ectocarpus siliculosus and Scytosiphon lomentarius in 1880; and these observations have been recently confirmed in the case of the former species by Sauvageau, and in the case of the latter by Kuckuck.
In these cases, however, the potential gametes may, failing conjugation, germinate directly, like the zoospores derived from unilocular sporangia.
Ectocarpus siliculosus, female gamete surrounded by male gametes.
Should I tell my child they were conceived using donated gametes?
Of course they may not be sterile in the sense of not being able to produce gametes.
In vitro fertilization studies will also be conducted using gametes recovered post-mortem to investigate the rate of fertilization by competing sperm.
In addition, 60 units could also represent a gamete about to divide to form 2 gametes.
In flowering plants, anther s produce pollen which contains male gametes, and the embryo sac within the ovary contains a female gamete.
Webber, and more recent work enables us to assume that all cycads produce ciliated male gametes.
This process is used in the production of haploid gametes.
The gametes ..