植物同源四倍体生殖特性及DNA遗传结构的变异

由于染色体加倍过程中的加倍因素和非加倍因素的影响, 同源四倍体的DNA遗传结构较其起源二倍体产生了变异, 进而导致其表现型发生相应的变异。和其起源二倍体相比, 同源四倍体的表现型变异表现在以下几个方面: 雌雄配子育性降低; 花粉(2n)的体积明显增大; 部分胚囊内卵细胞、助细胞及反足细胞数目有所增减; 自交繁殖过程中, 花粉的萌发及生长速度较慢、花粉管的形态部分畸形、部分极核受精过程及受精细胞(与精核结合的极核或卵)的进一步发育状况异常; 大多数育性或结实率会有不同程度的降低, 但降低的程度有因自交繁殖世代的推移而逐渐减小的趋势; 就一些植物种类而言, 同源四倍体有较好的远缘杂交亲和性。     

褪黑激素生理特性及应用

对褪黑激素的产生、合成、检测方法、对生殖的调控和应用及最新的研究成果等作了综述。     

The moral complexity of sperm donation

Sperm donation is a widely accepted and increasingly common practice. In the standard case, a sperm donor sells sperm to an agency, waives his parental rights, and is absolved of parental responsibility. We tend to assume that this involves no problematic abandonment of parental responsibility. If we regard the donor as having parental responsibilities at all, we may think that his parental responsibilities are transferred to the sperm recipients. But, if a man creates a child accidentally, via contraception failure, we tend to assume that the man does indeed have parental responsibilities. Assessing these contrasting conclusions requires a theory of parental responsibility. I analyse prevalent theories of what makes someone parentally responsible and show that none of these theories can withstand scrutiny. I propose a new theory of parental responsibility, which, I argue, is more plausible than the alternatives. My theory of parental responsibility is based on our ownership and control over hazardous materials, namely, our gametes. I show that neither my theory, nor the theories I reject, can support our contrasting intuitions. I conclude that sperm donors are fathers, with parental responsibility. I argue that the alternative conclusion, that neither sperm donors nor accidental fathers are parentally responsible for their resulting offspring, is less plausible. I then consider whether parental responsibility can be transferred and argue that it is far from clear that it can. Finally, I address objections and consider some practical implications of these views.     

EXISTENCE: WHO NEEDS IT? THE NON‐IDENTITY PROBLEM AND MERELY POSSIBLE PEOPLE

In formulating procreative principles, it makes sense to begin by thinking about whose interests ought to matter to us. Obviously, we care about those who exist. Less obviously, but still uncontroversially, we care about those who will exist. Ought we to care about those who might possibly, but will not actually, exist? Recently, unusual positions have been taken regarding merely possible people and the non‐identity problem. David Velleman argues that what might have happened to you – an existent person – often doesn't merit moral consideration since the alternative person one would have been had what might have happened actually happened is a merely possible person about whom one has no reason to care. He argues that his way of thinking can eliminate the non‐identity problem. Caspar Hare argues that merely possible people have interests and are morally relevant. He argues that we can solve the non‐identity problem by rejecting the view that merely possible people are morally irrelevant. Both Hare and Velleman argue that focusing on one's de dicto rather than on one's de re children can help us avoid the non‐identity problem. I analyze the role that merely possible, nonexistent hypothetical entities ought to play in our moral reasoning, especially with regard to procreation. I refute both Velleman's and Hare's views and demonstrate the difficulties we encounter when we try to apply their views to common non‐identity cases. I conclude with the common‐sense view regarding who matters, morally: only those who do, did, or will exist.     

Procreative reasons-relevance: on the moral significance of why we have children

Advances in reproductive technologies – in particular in genetic screening and selection – have occasioned renewed interest in the moral justifiability of the reasons that motivate the decision to have a child. The capacity to select for desired blood and tissue compatibilities has led to the much discussed 'saviour sibling' cases in which parents seek to 'have one child to save another'. Heightened interest in procreative reasons is to be welcomed, since it prompts a more general philosophical interrogation of the grounds for moral appraisal of reasons-to-parent, and of the extent to which such reasons are relevant to the moral assessment of procreation itself. I start by rejecting the idea that we can use a distinction between 'other-regarding' and 'future-child-regarding' reasons as a basis on which to distinguish good from bad procreative reasons. I then offer and evaluate three potential grounds for elucidating and establishing a relationship between procreative motivation and the rightness/wrongness of procreative conduct: the predictiveness, the verdictiveness, and the expressiveness of procreative reasons.     

First,do no harm: Generalized procreative non‐maleficence

New reproductive technologies allow parents some choice over their children. Various moral principles have been suggested to regulate such choices. This article starts from a discussion of Julian Savulescu's Principle of Procreative Beneficence (PPB), according to which parents ought to choose the child expected to have the best quality of life, before combining two previously separate lines of attack against this principle. First, it is suggested that the appropriate moral principles of guiding reproductive choices ought to focus on general wellbeing rather than prioritizing that of the child and, second, that they ought to be non‐maximizing (e.g. seeking the ‘good enough’ or to avoid harm). Though neither of these suggestions is entirely novel, combining them results in a new, and arguably more plausible, principle to regulate procreative choices, which I call the Principle of Generalized Procreative Non‐Maleficence (PGPNM). According to this principle, the primary obligation on parents is not to cause harm to other people through their reproductive choices.     

Upsetting the balance on sex selection

It is widely assumed that the strongest case for permitting non‐medical sex selection is where parents aim at family balance. This piece criticizes one representative attempt to justify sex selection for family balance. Kluge (2007) assumes that some couples may seek sex selection because they hold discriminatory values, but this need not impugn those who merely have preferences, without evaluative commitments, for a particular sex. This is disputed by those who see any sex selection as inherently sexist because it upholds stereotypes about the sexes. This article takes an alternative approach. I argue that, even if we accept that preference‐based selection is unobjectionable, a policy permitting selection for family balancing does a poor job of distinguishing between value‐based and preference‐based selection. If we wish to permit only preference‐based sex selection we should seek to identify parents’ motives. If we wish to justify a family balancing policy, other arguments are needed.     

ON THE SUPPOSED MORAL HARM OF SELECTING FOR DEAFNESS

This paper demonstrates that accounting for the moral harm of selecting for deafness is not as simple or obvious as the widespread negative response from the hearing community would suggest. The central questions addressed by the paper are whether our moral disquiet with regard to selecting for deafness can be adequately defended, and if so, what this might entail. The paper considers several different strategies for accounting for the supposed moral harm of selecting for deafness and concludes that the deaf case cannot be treated in isolation. Accounting for the moral harm of selecting for deafness necessarily entails moral implications for other cases of procreation and procreative decision‐making, including unassisted coital reproduction. The lesson to be learned from the deaf case is that we need norms that govern not just the use of reproductive technology, but procreation and procreative decision‐making in all of its various forms.     

Why Gametes are not Like Enriched Uranium

According to Rivka Weinberg, gametes are like enriched uranium: both are hazardous materials. Exposing human beings to enriched uranium can result in radioactivity and decreased life expectancy, while exposing sperm and ova to each other can result in the creation of needy innocent persons with full moral status. Weinberg argues that when we engage in activities that put our gametes at risk of joining with others and growing into persons, we assume the costs of that risky activity. She calls this the Hazmat Theory of parental responsibility. The theory is novel and important, and has far‐reaching consequences for the ethics of procreation, parenting, and population, implying among other things that that the only way to avoid acquiring parental responsibilities may be to “abstain from sexual intercourse or surgically interfere with our gamete‐release system.” For these reasons the theory merits careful scrutiny. In this article I criticize the theory's account of how parental responsibility is acquired and its treatment of the standard of care expected of gamete possessors, and argue that it fails to properly account for a distinction between procreative costs and parental responsibility. Even if gametes are hazardous, it does not follow that parental responsibility in Weinberg's sense is acquired whenever one brings new persons into existence.     

Lessons from Queer Bioethics: A Response to Timothy F. Murphy

‘Bioethics still has important work to do in helping to secure status equality for LGBT people’ writes Timothy F. Murphy in a recent Bioethics editorial. The focus of his piece, however, is much narrower than human rights, medical care for LGBT people, or ending the HIV/AIDS pandemic. Rather, he is primarily concerned with sexuality and gender identity, and the medical intersections thereof (i.e. DSM diagnosis; access to SrS or ARTs). It is the objective of this response to provide an alternate account of bioethics from a Queer perspective. I will situate Queer bioethics within Queer studies, and offer three ‘lessons’ that bioethics can derive from this perspective. These are not definitive rules for Queer bioethics, since it is a field which fundamentally opposes categorizations, favoring pastiche over principles. These lessons are exploratory examples, which both complement and contradict LGBT bioethics. My latter two lessons – on environmental bioethics and disability – overlap with some of Murphy's concerns, as well as other conceptions of LGBT bioethics. However, the first lesson takes an antithetical stance to Murphy's primary focus by resisting all forms of heteroconformity and disavowing reproduction as consonant with Queer objectives and theory. The first lesson, which doubles as a primer in Queer theory, does heavy philosophical lifting for the remainder of the essay. This response to Timothy F. Murphy, whose work is certainly a legacy in bioethics, reveals the multiplicity of discourses in LGBT/Queer studies, many of which are advantageous – even essential – to other disciplines like bioethics.