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Don't try to bluff a physicist in molecular biology

I remember this funny english book series, with the title "Bluff your way in ....", wherein "...." can be anything from history, philosophy to quantum mechanics or AI. As a physicist/biophysicist working in genetics and molecular biology research, I never felt the necessity to fake anything, though. Because both disciplines are very logical, complex and, (in case of genetics) even axiomatic. So quite suitable for a physicists brain to find enough challenges.
And I met many biologists and even medics who, on the other hand, feel a great attraction towards logic and quantitative thinking. But this week I had 2 really shoking encounters with colleagues, of whom one is even an institute director in molecular biology. Both have a PhD in biology, one is a full professor, the other a PI in cytogenetics. The cytogeneticist started to argue with me about the status of mammalian cell nucleus during mitosis (i.e. cell division, when the chromomes condense and become visible). The guy (who published many papers in cancer cytogenetics) was convinced that the chromosomes in metaphase are still confined within the nucleus. I told him that in metaphase there is no nucleus any more, because the nuclear envelop disappeares, and hence the condensed chromosomes are in the cytoplasm. He (at the age of 60 or so) had never heared about this.

In mammalian cells, chromosomes in metaphase are not confined in a nucleus any more, but entirely located in the cytpplasm.

And today I had a talk aside a thesis committee meeting with the mol.biol. professor. The guy really thought that mRNA splicing is happening in the cytoplasm, rather than in the nucleus. This is fundamentally so wrong, that it really made be jaw-dropping. Thats probably the whole difference between prokaryotes (nucleus-less bacteria) and eukaryotes (yeast, plants, animals, all of which have a nucleus in their cells). All organisms with a nucleus (eukaryotes) used to splice most of their messanger RNAs. Prokaryotes simply can not do this; their cells have not the necessary enzymes to do this complicate process. Therefore it is also logical that eukaryotic cells do mRNA splicing in their nuclei, and not in cytoplasm. 

Splicing of ncRNA into the mature mRNA is a process entirely in the nucleus. Only the spliced mRNA is exported to the cytoplasm (in order to be translated into proteins at the ribosomes)

For the mol.biol. professor (64 years old, 1 year before retirement), this was new information (hic!). One has to know that he is not only head of an institute, but also doing the exams for master- and doctoral-students (in molecular-biology, as one would easily guess).
So who has faked his entire professional career here ? Me, a self-trained geneticist with biophysic PhD, or them with their biology/molecular biology degrees ? I don't think that I am a nerd, such as the notorious Sheldon Lee Cooper, Ph.D., Sc.D from the freak show "Big Bang Theory". But at least I can put one and one together, and maybe in contrast to the biologists, who in part are still trained in the tradition of botanical encyclopedists, I always want to get a more comprehensive picture. And for me such a comprehensive picture of the processes in living organisms should be free of contradictions.
The two mechanisms described above, chromosomal segregation during metaphase and pre-mRNA splicing, are absolute essential processes that mark a cornerstone of higher evolution. Random chromosomal segregation outside of a nucleus not only happens in somatic cells a thousand of times every minute throughout our body, but it also takes place during meiosis in our reproductive organs (generation of sperms and oocytes). Sexual reproduction allows a much faster genetic drift as compared to asexual reproduction (clonal expansion), in which only genetic mutations could generate heritable variations in a phenotype. mRNA splicing is also a rather recent "invitation" by nature. Whereas the earliest know prokaryotic living cells (of the Archea domain) appeared on earth about 3.5 billion years ago, the first eukaryotes entered the stage of nature approximately 1.6–2.7 billion years ago (I can not remember the exact date sorry !!!). Splicing makes it possible to generate in multicellular organisms (metazoa) a huge variability of cell types, by differentially splicing the 35 thousand genes (estimation from the human genome) into at least 10 times more different mRNA species, which later can give rise to several hundred thousand different proteins. This makes the rather small genome of higher vertebrates (in comparison to protozoae fungi or even plants) so much more versatile. By fully exploiting the potential of differential splicing, higher vertebrates can much quicker respond to environmental challenges. Our immune system and our highly complex and adaptive brain makes heavy use of constantly changing the splicing pattern of some essential genes, thereby generating a lot of cellular plasticity.
I was shocked that the english Wikipedia does not mention mRNA splicing at all in the article on eukaryotes. Thats surprising, considering Wiki shall summarize the common knowledge of mankind.  Well, seems that again it needs a physicist to edit such a proto-type molecular biology entry. I promise in the next few days, I will add an extra chapter on the Wikipedia eukaryotes article and provide the link here on my blog post. Stay tuned, please.

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