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15

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 ...


13

From a certain point of view you could argue that our bodies have an inherently limited lifespan; Telomeres are extensions to the end of chromosomes that prevent damage or loss of genetic information during cell division. Telomeres are not replaced (in normal cells), which gives rise to a replicative lifespan; the number of times a cell can divide before ...


8

Cell-cell adhesion is a well-regulated mechanism, cells don't just stick together randomly, this interaction is mediated by specific molecules on the cell surfaces. The responsible proteins for that are the Cell Adhesion Molecules (CAMs) like integrins, cadherins and selectins. Which of these CAMs are present on the surface of a cell determines if those ...


7

The answer is more or less yes. Normally Firebugs (Pyrrhocoris apterus) go through 5 nymph instar stages (as do most Hemiptera), where they resemble the adults more and more as they grow. Only adults are winged and have have functional reproductive organs. This type of metamorphosis is called hemimetabolous or simple metamorphosis (in contrast to ...


6

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 ...


5

Cell differentiation, cell fate and cell mapping is an interplay of accessible evolutionary strategies/programmes and responses to dynamic environmental cues such as specialized hormones (e.g. morphogens) and physical parameters and constraints. That is putting it very broadly. It is a complex issue, if L. Wolpert's PLOS assays are any indication. I compiled ...


5

Many genetic studies in this area have found that variation in serotonin receptors associates with differences in a number of personality traits. That one gene, or a very small number, turns up time and time again for something so complex as human personality makes me a bit suspicious. Other factors at play: Family dynamics Culture and cultural norms ...


4

The problem you are looking for is called the "Nature vs nurture" debate. Lots of scientists have written lots of books and papers and done lots of studies on the subject. As you can see, the title of the debate already includes the two main concerning factors: nature (genes) and nurture (environment). These of course each include a variety of ways in which ...


4

Wikipedia has a page listing cell types which classifies their origin as endodermal or ectodermal. I haven't been able to find a source for a complete lineage of all cell types, and I have gained the impression that there is no complete picture, except in some specific cases such as the haemopoietic lineage. Here is a TEDX talk by a researcher in the ...


4

This is a very general question. The "developmental sequences" are just genes like any other. Like all genes they are semi-randomly distributed through the genome. While there are gene-rich and gene-poor areas in the genome, with some exceptions --notably the homeobox genes--, genes are not grouped by function. As to how they are accessed sequentially, that ...


4

No. In fact the lens of the eye, which is nearly optically perfect in humans, does not change or grow after it is fully formed around week 26 of gestation. Interestingly this is why one of the cues for identifying young children is having small faces with large eyes. This also the case for puppies and cats and other animals, who are mostly cuter when they ...


4

First of all, I should quote the sentence from the MOST reliable ophthalmology sourcing in the world - American Academy of Ophthalmology: Section 11 - "Lens and Cataract" "The equatorial diameter of the unfixed human lens measures 2 mm at 12 weeks and 6 mm at 35 weeks. Both the growth and the maturation of lenticular fibers continue throughout life." The ...


3

Hands are complicated and the genetic machinery behind their shape doubly so. It's easier to figure out worm segments first, and then work up from there. An egg has head/tail information encoded in it even before fertilization: see here You can imagine the first or second cell division would give a 'head' cell with higher concentration of head polarity ...


3

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 ...


3

Just so that someone answers this question so that the moderators have less work to do: The fundamental reason why embryos don't get massacred by the maternal immune system is because of the placenta and several of its functions. Three mechanisms are: 1) Secretion of neurokinin B, which is also secreted by parasites to avoid detection of the host. 2) The ...


2

Shuster, SM & C Sassaman (1997) Genetic interaction between male mating strategy and sex ratio in a marine isopod. Nature 388: 373-377 As described in this paper, the chromosomal system of sex determination in Paracerceis sculpta is ZW=females, ZZ=males. Genetic evidence indicates that the morph of a ZZ male is determined by a second locus, Ams ...


2

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 ...


2

First let me agree with the commenters that your question doesn't really make sense. Nonetheless here's an example that you may find interesting. Arachnocampa are insects that spend almost their entire lives as larva. These larva spin silk trap lines which capture and poison prey. They can only live in windless places (wind will mix up the lines) so to lure ...


2

These two papers[1] [2] argue that bcd is a direct activator of hb, although be aware that this does not rule out downstream events feeding back to further activate hb. (In fact, given the complexity of the embryonic gene network, it is likely that both mechanisms have a role.) Struhl G, Struhl K, Macdonald PM. 1989. The gradient morphogen bicoid is a ...


2

As far as I remember, Fibonacci patterns emerge in plants from hormone gradients. I.e. an apical meristem forms a leaf where the auxin concentration is highest, and already existing leafs lower auxin concentration, leading to some negative feedback. See e.g. http://www.sciencedirect.com/science/article/pii/S1360138507000581 or ...


2

From a quick look at the paper @ChinmayKanchi links to (Palmer, 2004) it seems that: All living vertebrates possess a heart that is conspicuously asymmetrical and normally displaced toward the left (Fishman & Chien, 1997). So the heart orientation seems to be evolutionary conserved in vertebrates (as are many fundamental traits), and no specific ...


2

I asked my professor, and the answer appears to be differences in both the generation and the final product. Free chromosome fragments are created through irradiation/other damage of the germline in one animal. Through a series of crosses, it is possible to introduce individual fragments (containing a duplication of your gene of interest, as well as a ...


2

@Alexandria Jak/Stat are two families of proteins which mediate signals through phosphotyrosines. JAK is a tyrosine kinase which binds to cell receptors and STAT is dimerized by JAK action. JAK specificity seems to be your question. A specific JAK protein (e.g. JAK1 or JAK2..) may mediate for different receptors in different cells. There may be ...


2

Normally, cells do not proliferate without a "command". The "zones of genetic activity" you mentioned are defined by gradients of morphogenic molecules (and cell interactions). In the adult organism the original "map" of concentrations of these molecules is already realized and the pattern they defined before is no longer present. Another closely linked ...


2

In hair and nail growth new cells are added to the bottom. These cells are produced at the follicle. There are three stages called: Anagen : active growth Catagen : end of active growth Telogen : total stop of follicular growth I don't know what you mean by like grass but both nails and hair have a first in first out order. Feathers present a ...


2

Quoting from some parts of Sean Carroll's book - Endless forms most beautiful, I have tried to provide you with an answer but, remember that this can never suffice for the reading of this great book. Yes, we do understand how the hox genes' expression is regulated. From page 126-127 ......The establishment of these Hox zones and their subsequent action ...


2

You might be interested in this book When writing Hox Gene collinearity (or colinearity as it is often misspelled as explain in wiki!) on Google scholar or WebOfKnowledge you will get many results on the subject. It is still today an ongoing debate. Below are some sentences I pick up from these articles. It is certainly hard to understand as I hardly ...


2

Physalia and Siphonophorans in general are multicellular Metazoans. But the whole discussion is about modularity on the level of individuals: Siphonophorans are colonial organisms, which means they are composed of multiple individual polyps and medusae. This is in fact quite common among Hydrozoa, but in Siphonophora the degree of integrity and function ...


1

Terdon is right on the money when it comes to how is the coordination done, and I know of at least one student working on this for her thesis. However, to answer your other question directly, there was a great review in 2010, which was taught in my genetics class that year. It is important to note that we still don't know all the genes that are involved ...


1

Wild ducklings, like these baby Mallard ducks, are in fact typically only partly yellow: Photo by TheBrockenInaGlory via Wikimedia Commons, used under the CC-By-SA 3.0 license. While I'm no expert, I would guess that the mottled yellow-brown coloring of the juveniles is, at least partially, protective coloration, just like the somewhat similar pattern on ...



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