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There is some evidence that fetal development under zero gravity conditions might be problematic. Wakayama S, Kawahara Y, Li C, Yamagata K, Yuge L, et al. (2009) Detrimental Effects of Microgravity on Mouse Preimplantation Development In Vitro. PLoS ONE 4(8): e6753. doi:10.1371/journal.pone.0006753 The paper is here. These authors studied aspects of ...

Great question, and one about which there has historically been a lot of speculation, and there is currently a lot of misinformation. I will first address the two answers given by other users, which are both incorrect but have been historically suggested by scientists. Then I will try to explain the current understanding (which is not simple or complete). My ...

Charnov and Ernest (2006) present data on offspring number per year and neonatal mass for 532 species of mammals. The two are related by the linear regression equation: ln(offspring/year) = 2.4 - ( 0.3 * ln(neonate mass) ) Giant panda neonates weigh 100-200 g and are weaned at 46 weeks. So, according to the regression, pandas should have, on average, 2.8 ...

Fetal testis produces testosterone from cholesterol. There is a peak of production around 15 weeks of gestation (the "masculinization programming window"). So the genotype of the fetus can affect testosterone levels directly via effects on the biosynthesis of the hormone, or indirectly by defective regulation of the pathway's activity. However, exposure to ...

The propensity for heterozygotic twins seems to be driven primarily by genetics, with additional factors playing a role (http://152.98.160.29/contents/p/staff/CV162Lewis_UQ_Copy.pdf', info site): hormones ("Mothers of fraternal twins tend to be taller, and have earlier and shorter menstrual cycles") ethnic background (which is really genetic) - African ...

This is a very interesting question. Many people have researched this topic, and many still are. But regardless, I had never heard of Alan Turing's contributions, so thank you! First of all, I cannot actually find who first coined the term morphogen. Though people had hypothesized that chemicals could play a critical role in development through much of the ...

In humans, the amnion (amniotic sac) persists from the primitive amniotic cavity1. One side of this is formed from the cytoblast (a prismatic epithelium) and the plasmodioblast. Together these two layers are the ectoplacenta or chorion. They are also referred to as Rauber's layer. These replace the lining epithelium of the uterus, whereupon internal ...

There is variance in egg shape; sea-birds often use a more pear or conical shaped egg to prevent it from rolling off the cliff (where they nest) if it is disturbed. Some reptiles lay very spherical eggs (some turtles) whereas some reptiles lay very elongated ones (see black pine snake eggs). I imagine that we don't see square eggs because they would be ...

Plants have a simpler anatomical structure than mammals (is anatomical the right word, or would physiological be more appropriate?). Mammals on average don't have more genes than plants, so my understanding is that this additional complexity is the result of finer and more complex regulatory mechanisms. When you remove or duplicate an individual gene in an ...

It's old and I can't get access to this issue of the Annals of the New York Academy of Science, but it looks like it has some relevant information. Sifting through the abstracts it seems the vasculature of the fetal liver is completed at around 8 weeks although is still different to the adult vasculature because of the umbilical vein. The growth of the organ ...

Wikipedia actually covers this: Most bilateral animals, including all the vertebrates, are coelomates. Now, some coelomates have subsequently lost their coelom but primates (actually, I believe, all vertebrates) are not among them. In humans, the coelom forms, amongst others, the pleural cavity. So, yes: humans do have a coelom that partitions into ...

In animals, polyploidy is not tolerated and very few polyploid species are known to exist. Those that do exist are usually asexual, parthenogenetic, or hermaphroditic. Most of the problems resulting from polyploidy occur during synapsis of homologues during prophase I. As plants do not have a chromosomal mechanism for sex determination, ...

Human embryogenesis is much more complicated than the more general and simplified picture given in your 1st figure. For details, please study http://en.wikipedia.org/wiki/Human_embryogenesis To point out the most distinctive features which might have led to your confusion: Before gastrulation, the blastocyst cavity is formed. Only the inner cell mass ...

Nutrition and environment don't have a huge affect, if any, that I could find. Age can, as women above 35 have a greater propensity for bearing twins. http://en.wikipedia.org/wiki/Twin#Fraternal_.28sororal.2Fdizygotic.29_twins However, because fraternal twins can be the result of a gene on the X-Chromsome, the answer is yes in this specfic case. ...

I would think this is very much still "used." 60 years later, we finally have the first experimental support for it: In this blog article about this journal piece the authors studied the ridges that form on the roof of mouse mouths. They manipulated the signaling molecules that induce their formation and observed changes in line with Turing's theory. Of ...

In addition to @mgkrebbs response, I'd add that many genes are controlled by epigenetic mechanisms which may mask one of the parental copies by methylation. This can be a specific effect where, the active gene is specifically from either the father or the mother. Mosaicism, where one copy of gene is randomly inactivated in any given cell, is also possible. ...

First, while half the chromosomes come from each of the two parents, these two sets of chromosomes are not termed X and Y (they would usually be called maternal and paternal). The terms X and Y refer to potential members of just one pair of the 23 pairs (in humans) of chromosomes, and X chromosomes can come from either the mother or the father. The ...

Basically a summary and details-filled version of the above. Based on ln(number of offspring/year) = 2.4 - ( 0.3 * ln(neonate mass) ) (c.f. Charnov EL and SKM Ernest. 2006. The Offspring‐Size/Clutch‐Size Trade‐Off in Mammals. American Naturalist 167:578-582.) litter/year = 1 / (pregnancy duration in years + weaning time in years) it can be deduced ...

I found that a search through Google Books was helpful... While without the excretion of feces, it might seem as if the liver would not be active, but the liver tissue is not only active in development and tissue generation but serves direct physiological function as well. After initial phases of development, the liver produces fetal red blood cells which ...

The answers to most of your questions are under active research and there are many unknowns. Understanding this process is one of the main goals of developmental biology. So, try to set reasonable goals for your project, mainly by seeing where you have sufficient data to work with. I would start with reading some basic textbook on developmental biology. ...

I would start with Developmental Biology, 9th Ed. It's not up to the absolute cutting edge, as it was published in 2010, but it has a lot of good stuff in it. Wikipedia is a decent resource to get very brief overviews on certain subjects, but a lot of the life science articles I've read tend to be lacking, as opposed to the physics and math articles, for ...

Trying to answer this question in a few lines is a tedious task. Mostly I'm not sure that as of today we know all there is to know about it. I'll try to give you some hints though. The process is called embryogenesis. The zygote (or ovum) undergoes rapid mitotic divisions with no significant size growth which will lead to the development of an embryo. ...

The location is exactly tuba uterina infundibulum, source, since the processes results in the following things before LH peak: The correct placement of the uterine tube infundibulum upon the ovarian surface The rupture of the follicle wall and the flow of the follicle fluid with the oocyte into the infundibulum The inhibition of the ...

My professor says that The yolk sac is not connected to the mechanism of polyspermy or monospermy. [Amount of yolk inside the oocyte is then again.] The oocytes of reptiles and birds are yolk rich - polylecithal for instance. where lecithal = yolk containing and some pieces of information about here.

Embryonic disc forms on top of yolk during cleavage on chicken embryo, while between amniotic sac and yolk sac inside blastocyst after implantation on human embryo. Some further processes take place on and in the embryonic disc: specifically these here during the week 3. Embryonic disc formation includes still during the 3rd week of development: ...

It's not a totally answerable question, since some types of cells are going to divide more times than others. But for an estimate, take as a starting proposition that there are 1 trillion cells in the adult human body. [1] The average weight for a human is 62kg. [2] Average birth weight is about 3.4 kg. [3] So that implies roughtly (3.4/62)* 1 trillion ...