Origin of the germ cell line

摘要: The definitive germ cell line usually is considered to begin with the appearance of primordial cells (PGCs). As we shall see, for a few selected examples, PGCs are identified first in posterior blastoderm certain insect embryos, floor blastocoel anuran frogs, anterior extraembryonic endoderm chicks and yolk sac mammals. It tempting make generalization from these findings that diverse animals arises within or its equivalent prior organogenesis. However, on basis morphological features. This criterion alone may be insufficient defining beginning line. Cells which do not particularly look like but have developmental potential PGCs, express gene products specific might present at earlier times other sites during embryogenesis. If this were shown case, one argue by criteria such should called PGCs.