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This layer functions in protection by allowing the embryo to develop in a hypotonic solution so the cell will not burst. [5] Finally, the third set of blastomeres are the deep cells. These deep cells are located between the enveloping layer and the yolk syncytial layer and eventually give rise to the embryo proper. [1]
To begin transcription of zygotic genes, the embryo must first overcome the silencing that has been established. The cause of this silencing could be due to several factors: chromatin modifications leading to repression, lack of adequate transcription machinery, or lack of time in which significant transcription can occur due to the shortened cell cycles. [7]
The Zebrafish Information Network is an online biological database of information about the zebrafish (Danio rerio). The zebrafish is a widely used model organism for genetic , genomic , and developmental studies, and ZFIN provides an integrated interface for querying and displaying the large volume of data generated by this research. [ 2 ]
Pregnancy has been traditionally defined as the period of time eggs are incubated in the body after the egg-sperm union. [1] Although the term often refers to placental mammals , it has also been used in the titles of many international, peer-reviewed, scientific articles on fish.
In seed plants, the embryo will develop one or more "seed leaves" . By the end of embryogenesis, the young plant will have all the parts necessary to begin its life. Once the embryo germinates from its seed or parent plant, it begins to produce additional organs (leaves, stems, and roots) through the process of organogenesis.
In embryology, Carnegie stages are a standardized system of 23 stages used to provide a unified developmental chronology of the vertebrate embryo.. The stages are delineated through the development of structures, not by size or the number of days of development, and so the chronology can vary between species, and to a certain extent between embryos.
The embryo becomes embedded in the endometrium in a process called implantation. In most successful pregnancies, the embryo implants 8 to 10 days after ovulation. [7] The embryo, the extra-embryonic membranes, and the placenta are collectively referred to as a conceptus, or the "products of conception".
Sexual differentiation is the process of development of the sex differences between males and females from an undifferentiated zygote. [1] [2] Sex determination is often distinct from sex differentiation; sex determination is the designation for the development stage towards either male or female, while sex differentiation is the pathway towards the development of the phenotype.