Gametogenesis Spermatogenesis Pembentukan spermatozoa Di testis MAKALAH-RADIOLOGI; University of Jember; FMIPA – Winter IVG has four important foreseeable applications: to provide an in vitro model for the study of human gametogenesis (the formation of gametes) and diseases of. my name is suwaibah khaira, i am a college studentedit. Advisors: edit. Drafts · Laporan Pratikum Gametogenesismore. by Suwaibah Rao.
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The Principle of Procreative Beneficence PB holds that when a couple plans to have a child, they have significant moral reason to select, of the possible children they could have, the child who is most likely to experience the greatest wellbeing — that is, the most advantaged child, the child with the best chance at the best life. For example, many couples defer conceiving until they are in a better financial or social situation in an attempt to give their child a better life.
Or a woman who is currently suffering from rubella may defer conception until she has recovered to prevent giving birth to a severely impaired child. In both of these cases, parents are choosing to have one child, who can expect a better life, over another, who could expect a worse life. Most people believe that such choices are morally permissible, if not morally required.
PB extrapolates from our intuitions about such cases to cases involving selection using technological means, such as pre-implantation genetic diagnosis.
PB does not posit gametoegnesis absolute moral obligation — it does not dictate what people must do. Instead it holds that there is a significant moral reason to select the best child, but one that must be weighed against other reasons.
Many objections have been raised to PB. Recent advances in stem cell research may provide a solution to this problem. Recent research suggests that it may become possible to derive gametes eggs and gamstogenesis from human stem cells in vitroa process which we will term in vitro gametogenesis IVG.
Major advances in this technology have been made in the mouse.
Both sperm-like 13 and egg-like 14 cells have been derived from murine mouse embryonic stem cells mESCs in vitro. One laboratory also maoalah the production of live offspring following fertilization of natural mouse eggs with sperm-like cells derived from mESCs. IVG, based on this research, would involve a number of steps. One possibility is that the genetic material from a somatic body cell from a patient would gamftogenesis transferred into an enucleated oocyte an egg that has had its nucleus removed via somatic cell nuclear transfer SCNTcreating an embryo which would be a clone of the patient.
This cloned embryo would then be allowed to develop to the blastocyst stage. Developing germ cells immature gametes would then be harvested from the inner cell mass of the embryo and placed in culture to mature. Once the mature gamete had formed, the remainder of the procedure would follow current IVF techniques fertilization followed by implantation.
Alternatively, new research suggests a method that would avoid the need for SCNT. It has been shown gametofenesis adult mouse fibroblasts can be dedifferentiated to form immature cells that have characteristics of ES cells.
These are known as induced pluripotent stem iPS cells. Stems cells could be derived directly from somatic cells, and could then gametoegnesis used to generate gametes. Ga,etogenesis has four important foreseeable applications: The main role of IVG in fertility treatment is likely to be the creation of a supply of eggs. While the natural supply of sperm is usually plentiful and easily obtainable, achieving a supply of eggs is much more problematic. Currently, if a woman wishes to employ assisted reproductive technologies, eggs must be harvested from her ovaries.
This procedure is not without risk and discomfort. Furthermore, a limited number of eggs can be obtained via this method. IVG could makqlah the need to harvest eggs, since they could instead be derived and produced in abundance from somatic cells.
Procreative beneficence and in vitro gametogenesis
In cases of infertility due to nonproduction of sperm, a similar approach could be used to produce sperm in large quantities. The ability to create large numbers of eggs or sperm through IVG greatly increases our capacity to select the best child possible.
Selection could occur in two ways: Whatever the method, the advent of IVG could allow us to select for a much larger number of traits than is currently conceivable. IVG may also offer new possibilities for genetic enhancement. Cells could be modified prior to gamete formation, most probably once an ES cell culture has been established 25 However, in this paper we focus on possibilities for selection, rather than enhancement.
We answer this question using a simple mathematical model. Suppose that a couple would like to select for 20 single gene traits which are carried on 20 different and unlinked autosomal loci.
Suppose further that at ten of these loci, alleles contribute recessively to the desired trait. That is, of the four possible combinations of alleles — which we might label RRRrgamettogenesisand rr — only rr confers the disposition.
Suppose that at the other ten loci, alleles contribute dominantly to the desired disposition, so that GametigenesisDdor dD individuals will possess the disposition — only dd individuals will lack it. Not every couple in the population will be capable of having a child with the desired genotype at each locus.
For example, suppose that a couple are RR and Rr respectively at one of mqkalah recessive loci. It will be impossible for this couple to have a child makalag the desired rr genotype at this locus. However, we can make some statistical observations about how likely it is that a randomly selected couple will be able to have a child gametogenrsis the desired genotype at a given locus.
In general, if the four different allele combinations at each locus are equally prevalent in the population male and femalethen a typical couple will be capable of having a child with the desired genotype at 6 of the 10 recessive loci, and 9 of the 10 dominant loci [see Appendix 1 ]. Thus, a typical couple would be capable of having a child with 15 of the 20 desired traits. Of course, the chance that a randomly selected couple would naturally have a child with all 15 desired traits is extremely small.
The chance that the couple would have a child with the desired genotype at a given recessive locus at which the desired genotype is possible would be significant at 0. The probability that they would have a child with the desired genotype at a given dominant locus at which a desired genotype is possible would be even higher at 0. There is only a one in chance of having a child with the optimal genotype through natural reproduction.
Our randomly-selected couple could, however, increase their chances of having the child with their preferred genotype by engaging in IVF and preimplantation genetic diagnosis. Suppose that ten embryos are created through IVF, and that the genotypes of each of these embryos at the 15 loci in question can be determined.
The probability that one of these embryos will have the preferred genotype will be:. This is much higher than the probability for a couple using natural methods. Now suppose now that our couple could create large numbers of embryos using IVG, followed by pre-implantation genetic diagnosis.
This would greatly improve gametogensis chances of finding an embryo with the optimal genotype. Suppose that 1, embryos were created.
The chance of finding an embryo with the optimal genotype will now be:.
Thus, the effect of using IVG could be highly significant. In the case that we have just presented, the couple were interested in selecting 20 single gene traits. But using IVG, it may also become feasible for a couple to select for desired polygenic traits. Thus, we could assume that the 20 loci considered in the above model all contribute to a single polygenic trait makalau a disposition to increased intelligence, or reduced risk of heart disease rather than to 20 distinct single gene traits.
In that case key results would be as follows. Under our assumptions, a typical couple would be capable of having a child with 15 of the 20 genes that contribute to the polygenic trait in many cases, having 15 of the 20 genes would be enough to have a significant effect on phenotype.
The Formation of Polyploidy on Cyprinus carpio Linn Punten Race by Heat Shocking Temperature
By enabling the creation of large numbers of gametes and embryos, IVG may allow the selection of traits in future children to a degree that has previously been inconceivable. The use of IVG to aid selection of children would invite different objections depending on whether it occurred at the level of embryos, as in the model described above, or at the level of gametes. In what follows we first address objections to the selection of embryos using IVG, then objections to the selection of gametes via IVG.
Finally, we discuss a number of general objections to the use of IVG to create the child with the best chance at the best life. In all cases, we consider only objections to pursuing PB via the use of IVG We leave aside objections that are equally applicable to the pursuit of PB using existing technologies.
Selection at the level of the embryo raises the thorny issue of the moral status of the embryo. While this application of IVG could facilitate the selection of more advantaged children, it would also involve the intentional creation and destruction of very large numbers of embryos. Thus, those who oppose all embryo destruction will also oppose this technology. Those that do not may be forced to decide whether the embryo has some or no moral status.
Each cycle of IVF ultimately results in the destruction of a small number of embryos. While initially embryos that are not implanted may be frozen, these embryos will only be stored for a finite duration and are then either destroyed, donated to another couple, or in some jurisdictions, donated to research.
However there are difficulties with the view that early embryos possess any significant moral status. Millions of embryos are die naturally every year due to spontaneous abortion. However, even knowing the extent of spontaneous abortion, most of us do not think that it is a major world problem on a par with war, famine or disease. Indeed, we think it would be absurd to give the elimination of spontaneous abortion the priority that is currently given, say, to the elimination of AIDS or cancer.
This suggests that we do not really believe that embryos have full moral status 33 Indeed, the fact that most of us feel little inclination at all to regard spontaneous abortion as an important public health problem suggests that we assign early embryos no significant moral status.
Some may be concerned that the destruction of embryos on a huge scale would be the beginning of a slippery slope to something more sinister. However this concern seems unfounded as research protocols draw a very clear line in embryonic development about how far we can allow embryos to develop and at what point they should be destroyed. While it may be true that it is difficult to identify a point at which moral status begins, this does not mean that no line can be drawn, and effectively enforced by regulators.
We do not claim to have shown that early embryos lack any moral status. We merely wish to emphasise two points. First, that the possible use of IVG in the name of procreative beneficence may force us to decide whether early embryos have any significant moral status. And second, that the view that they do have significant moral status faces some serious, though not necessarily intractable, problems.
Selecting gametes rather than embryos would avoid the destruction of large numbers of embryos, and hence would be significantly less ethically controversial than embryo selection. Gamete selection using IVG may require the creation and subsequent destruction of one embryo per parent, to serve as a source of ES cells, and eventually gametes.
Alternatively, it may be possible to eliminate the need for any embryo destruction by deriving induced pluripotent stem iPS cells directly from somatic gameyogenesis. Gametes derived from stem cells, or naturally-produced sperm from a fertile male, could then be screened to detect their genetic profile, and then the best combination of egg and sperm used to create an embryo. It would be universally agreed that gametes have little moral status.
But do they have any significant moral status? Although gametes have potential to create life, they are frequently allowed to die without fertilisation and this is of no moral gamtogenesis. Indeed contraception is aimed at preventing gametes from creating life, and this is not normally thought to be controversial. It appears that most people regard the death of gametes prior to fertilisation as being of little moral consequence.
As the number of traits being selected increases, the number of embryos or gametes required to allow effective selection increases dramatically. Limits on the number of embryos or gametes that can be produced or tested may thus constrain the number of traits that can be selected.