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Is the Human Embryo an Organism?
Published in Nicholas Colgrove, Bruce P. Blackshaw, Daniel Rodger, Agency, Pregnancy and Persons, 2023
Early human development is summarized in Figure 1.1. Briefly, upon sperm-egg fusion at fertilization, a single cell (the zygote) is formed (Figure 1.1A). The zygote divides rapidly, producing a number of smaller cells known as blastomeres (Figure 1.1B). By the second or third day following sperm-egg fusion, the blastomeres have formed a ball-like structure known as a morula-stage embryo (Figure 1.1C). Cell division continues, and by the fifth day, the embryo has grown to about one hundred cells and formed a fluid-filled structure known as a blastocyst (Figure 1.1E). At this stage, the first two committed cell types have arisen. The cells that make up the outer layer of the blastocyst are known as trophectoderm (TE). Inside the blastocyst is a cluster of cells, known as the inner cell mass (ICM).
Genetics and exercise: an introduction
Published in Adam P. Sharples, James P. Morton, Henning Wackerhage, Molecular Exercise Physiology, 2022
Claude Bouchard, Henning Wackerhage
The independent assortment of chromosomes from either parent at meiosis, together with the homologous recombination occurring at several sites along each chromosome, augments genetic diversity and ensures that a new zygote and eventually offspring receives a random mix of chromosomes and DNA variants from each parent. In addition, new mutations occurring in sperm or oocytes have a probability to be present in a zygote and be passed on to the offspring. This is not a benign phenomenon as a new baby typically carries up to 100 single-nucleotide changes that were not present in the germline of his or her parents (27).
Ethics Biology: Are There Ethical Genomes?
Published in Howard Winet, Ethics for Bioengineering Scientists, 2021
It may be stated that a sufficient number (referred to as power) of patients who share similar DNA will also express similar behavior. Therefore, DNA may be analyzed to localize the specific site(s) of the malfunction. It may be possible either to confirm a specific function of the gene set of interest by damaging target ACC sites and observing resultant behavior or by knocking out the relevant DNA sequences in zygotes and observing resultant behavior as the child grows up. Both of these experiments would violate the Helsinki Declaration.
Ethics Considerations Regarding Artificial Womb Technology for the Fetonate
Published in The American Journal of Bioethics, 2023
Felix R. De Bie, Sarah D. Kim, Sourav K. Bose, Pamela Nathanson, Emily A. Partridge, Alan W. Flake, Chris Feudtner
Fertilization of a human egg outside of the maternal body and subsequent successful implantation was first performed in 1978 in the United Kingdom, resulting in the birth of the famous “test tube baby” Louise Brown (Steptoe and Edwards 1978). In vitro fertilization (IVF) since then has become the cornerstone of assisted reproductive technologies, which in the United States in 2018 was involved in 1.9% of births according to data available from the Centers for Disease Control and Prevention (CDC 2018). Upon fertilization, the zygote is typically cultured for three to five days before it is implanted in the womb to become an embryo. In an experimental setting however, continued research efforts have led to optimization of culture conditions allowing human embryo culture until 14days conceptional age (CA)(Deglincerti et al. 2016; Shahbazi et al. 2016). In most jurisdictions, legal restrictions prohibit the culture of human embryos beyond 14days of development (Pera 2017). Although the authors of this experimental work invoke these legal reasons for not going beyond the two-week hallmark, their work and findings have been used to advocate for an extension of these legal and moral limitations (Morris 2017). In 2021, the International Society for Stem Cell Research (ISSCR) updated their guidelines, recommending that studies proposing to grow human embryos beyond the two-week mark be considered on a case-by-case basis, and be subjected to several phases of review to determine at what point the experiments must be stopped (ISCCR 2021; Subbaraman 2021).
Towards the selection of embryos with the greatest implantation potential
Published in Journal of Obstetrics and Gynaecology, 2021
Dalia Khalife, Antoine Abu-Musa, Ali Khalil, Ghina Ghazeeri
Because of the few observations during the morphological assessment, several investigators have accepted the challenge to show that morphokinetic development of embryos presents a broader image of the embryo behaviour. It has been shown to be advantageous in providing more information on the timing of events such as fertilisation, the extrusion of polar bodies and the timing of cellular divisions (Fréour et al. 2013; Muñoz et al. 2013). Morphokinetic parameters used to predict the formation of a zygote into a blastocyst were based on the duration of the first cellular division, the time interval between 1 and 2 cell embryo and the synchronicity from 2 to 4 cell embryo. The development to high-grade blastocyst can be estimated in the first 2 days of embryo culture (Kirkegaard et al. 2013), as it is correlated to an early cellular division, to a shorter time of second division (3 to 4 cells) between 9.33 to 12.65 h and shorter time of third division (5 to 8 cells) between 0 to 4 h (Montag et al. 2011; Hashimoto et al. 2012; VerMilyea et al. 2014).
The Non/Inhuman Within: Beyond the Biopolitical Intrauterine Imaginary
Published in Studies in Gender and Sexuality, 2021
Sarah Franklin describes the embryo as a basket category “describing everything from a conceptus, a zygote or a blastocyst to a reconstructed cell, a fertilized egg or an embryoid body” (2006, p. 167). The early intrauterine process from zygote to embryo is a dynamic happening over a number of weeks, involving one cell (the alliance of sperm and egg) rapidly evolving to become a ball of cells, and then to transform into a set of tubes. It is worth noting, as medical and visualizing technologies develop, that the embryo stage is rapidly becoming subject to what Sarah Franklin names “anxious attention”: Human embryos are now a vast and diverse population, imaged, imagined and archived in media as diverse as liquid nitrogen, DVDs, virtual libraries, t-shirts, logos and brandnames. (Franklin, 2006, p. 168)