12 votes

How does an embryo know where to grow limbs etc

You may want to look into "Evolutionary - Developmental Biology", which deals with how an embryo develops into a grown organism. Thus, by combinatorial specifying the identity of particular body ...
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7 votes
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which exact mechanism triggers the first cell differentiation after n divisions?

The first differentiation in human embryogenesis is from early blastomeres into trophoblast, which forms the outer layer of the blastocyst, and inner cell mass (ICM). It may be unsurprising then that ...
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6 votes

How does an embryo know where to grow limbs etc

I wanted to add some helpful references. The 6th edition of the Gilbert Developmental Biology textbook is available on NCBI bookshelf. It's a bit old (2000), but much of the information is still ...
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6 votes
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How late in a human pregnancy can a zygote split?

Identical twins Twinning occurring at the two cell stage or afterwards, up to and including the 16 cell stage, which translates to days 1 to 3 after fertilization, results in diamniotic, dichorionic ...
  • 2,228
5 votes

How scientists can be confident that human embryo tail is really a tail?

We can be sure it's a tail because it is an extension of the vertebrae, and we define "tail" as an extension of the vertebrae, among other things. tail tāl/ noun: tail; plural noun: ...
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4 votes
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Can a chicken really be hatched outside of the egg?

Yes it is real, in the sense that this protocol has been through a peer reviewed journal. Note that the embryo is developing outside the shell, not outside the egg. It is the fertilized egg that ...
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4 votes
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At what stage is the nervous system developed enough to interpret neuronal signals as 'pain'?

First, there is some confusion on your part about heart cells and pain perception. Heart cells generate an action potential intrinsically; they do not need the central nervous system to beat (your ...
4 votes
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Does the mesoderm evolve from the ectoderm or the endoderm?

In human,the mesoderm doesnot develop from the endoderm or the ectoderm.It develops from epiblast of the bilaminar germ disc stage. During the week 3 of development, the epiblast of the disc ...
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4 votes
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How does a cell distinguish left from right?

Developing symmetry is is just a matter of Homeotic genes creating axial patterning, genes that produce a chemical gradient across a cell or group of cells. This is how developing organisms orient ...
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4 votes

Why can human viruses that can't infect chickens be grown in embryonic chicken cells?

The measles vaccine uses an attenuated virus: one that has been modified to reduce virulence such that it is (hopefully) no longer harmful to the host but still retains the antigenic determinants to ...
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3 votes

Does a zygote express all genes?

The short answer is that no, a zygote doesn't express all genes simultaneously. A zygote is like any other cell, in that it represents a distinct phenotype. And like any other cell, this phenotype ...
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3 votes
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Embryo development terms

When in doubt go back to definitions I say (as I am now). cytoplasmic determinants: regulatory molecules located in specific distributions around egg cytoplasm Induction: process by which the ...
  • 397
3 votes

Unknown animal - What could it be?

The animal is very suggestive for Dog whelk-like mollusc removed from its shell. I try to mark the organs, do not rely on these marks as an absolut. Testis Renal vein Gill Mantle Prostate Osphradium ...
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3 votes

How long do zebra fishes remain transparent?

The upper limit of transparency time of zebrafishes is anywhere from two to three weeks for normal zebrafish for optimal high-resolution imaging. However, there is a modified species of Zebrafish ...
  • 1,634
3 votes
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Which process is needed to complete male reproductive development?

Regarding option C: Although it is correct that testosterone is converted into DHT, it is the former, not the latter, which is responsible for differentiation of the mesonephric (a.k.a. Wolffian) ...
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3 votes
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What is cytoplasmic localization?

"Cytoplasmic localization" is a very general term and it means that something is present in the cytoplasm. For instance (hypothetical but there are known examples), you can say protein-X is localized ...
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3 votes

How far is stem cell research from being to generate a new organ?

Sperm can already be generated using stem cells http://blogs.discovermagazine.com/d-brief/2016/02/25/scientists-grow-working-sperm-from-stem-cells/#.V-UADBV94o8 Also, heart, liver and kidney cells as ...
  • 3,028
3 votes

What is this part of blastula called and how is endoderm formed?

The blastocoel, as you say yourself, is a fluid-filled cavity (wikipedia) so it has no cells. Fig. 1 shows cellular and non-cellular regions of the blastocyst. Your questions on the formation of the ...
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3 votes
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Is a part of the spinal cord from the mesoderm?

The caudalmost part of the neural tube is formed by the caudal eminence. Isn't this mesodermal? No,the neural tube is not mesodermal at caudal end. According to Gray's Anatomy: At the time of ...
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3 votes

Has the gestation (pregnancy) period for humans always been 9 months?

human gestation period According to the link gestation period doesn't vary much between great apes. I don't see any signs that human are becoming "more complex". In fact human babies are uniquely ...
3 votes
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How can there not be purpose movement in the fetus until week 18, when a fetus can open its mouth and suck its fingers at week 11?

Swallowing (Nishino, 2013) and sucking (rooting reflex) are reflexes. The fingers may just happen to be in the vicinity of its oral region (they often are; Fig. 1.), and oh boy are babies keen to grab ...
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3 votes

Can a brain process auditory signals at 18 weeks of human development?

According to a concise review by Graven & Brown (2008) the development of the auditory system (Fig. 1) in the human is as follows: 15 weeks gestational age*: structural parts of the cochlea and ...
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3 votes

What type of movement is "spontaneous movement" if it isnt reflex movement and it isnt purposive movement?

Although I can't read the original article in Czech, from their abstract it is clear that all they mean in differentiating spontaneous versus induced movement is whether the experimenter manipulated ...
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3 votes

Cause of premature death in turtle eggs

Well, a real chance this is a genetic problem. How to test. For the next hatching, have some “normal” unrelated eggs nearby under the exact same conditions. If they also have higher mortality then ...
2 votes
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Negative role of Placenta

The placenta does not turn "hostile" to the mother or fetus. Placentation abnormalities can result in harmful situations, but these are a secondary result. Structural anomalies of placentation: ...
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2 votes
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Waste generation by embryo

Embryos still metabolize the nutrients delivered by the mother. The metabolism takes place in the cells, including in the developing organs. Metabolism produces waste products that must be removed. ...
2 votes

How does an embryo know where to grow limbs etc

yea the hox genes are essential for the the specification of the location but the actual growing of the limbs are determined by a series of protein and other factors. proximal limb contains fgf(...

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