Podcast #128: We chat with Kent C Dodds about why he loves React and discuss what life was like in the dark days before Git. Listen now.
55

Brian Hayes wrote a very interesting article from a mathematical point of view: http://www.americanscientist.org/issues/pub/the-invention-of-the-genetic-code especially the "Reality intrudes" section. Basically people had created fancy mathematical reasons why it has to be exactly 20. Nature, being nature, does not follow the reasoning, but has its own ...


52

There are two relatively common contagious cancers: Tasmanian Devil Facial Tumor, and Canine Transmissible Venereal Tumor. Both are truly contagious cancers, in that the cancer cells themselves are transmitted from one host to the next, and expand and cause disease in each successive host. (There was also a contagious cancer of hamsters, which has long ...


49

What do you mean by siblings? If by siblings, you accept cases of individuals having the same father but not the same mother, then of course, it is possible! Below, I will assume you are referring to full siblings (eventually twins). Age gap between twins According to the huffingtonpost, there is a case of two twins that were born 87 days apart. On ...


47

Short answer The article in particular that you reference is discussing the possibility of using a mechanism called gene drive. The concept of gene drive breaks the normal "rules" of inheritance and allows a gene to spread much more rapidly than normal in a population. Longer answer Gene drive depends on the idea of a selfish gene. There are naturally ...


44

Take a look at this little fellow: It's a flying squirrel — a shy little nocturnal rodent which lives in trees and, despite its name, does not actually fly. It does, however, have a skin membrane called a patagium between its fore and hind limbs which allows it to glide from tree to tree and thus evade ground predators. It's not hard to see how the ...


40

Yes. Far-red vision (>700nm) The ability for retinal-binding proteins to absorb far-red (between 700nm-850nm) light has been experimentally confirmed in this paper. While the authors did not attempt this in vivo in an animal model, they managed to use directed mutagenesis to induce a significant shift in the absorption peak of the chromophore of the ...


36

Going through the possible answers (A) Rates tend to be very high in most populations. This is a very unclear statement. What does "high" mean? In humans, the average mutation rate per reproduction per nucleotide is of the order of $10^{-8}$ (Rahbari et al., 2016) (hence of the order of 10 - 100 mutations for the whole genome). Whether someone wants to ...


33

There is a distinct difference between the 'genes' that we share, and the genome (the DNA) that the genes are made of. All humans (excluding genetic disorders) have the same genes, but the same gene in different individuals may have a slightly different DNA sequence, and this may be manifested in the different traits you can observe between people (eye ...


33

It is true that the Y chromosome is shorter than the X chromosome and that there are more genes on the X chromosome. Do men have fewer genes? One could (mis)understand three things in the expression "number of genes". Number of gene copies (see Copy Number Variation) Number of genes Number of alleles Thanks to @GerardoFurtado for correcting my ...


33

It is highly unlikely that there exist any protein that is made from completely identical nucleotide sequences across the entire human population. There will certainly be regions within a gene that are highly conserved, but there is little evolutionary pressure to conserve an entire gene's nucleotide sequence across the population. This is in part due to ...


31

The first modern humans evolved about 200.000 years ago in Africa. When they lost their body hair (or at least most of it), they needed some other protection of their skin from the sun - otherwise they are prone to develop melanoma. Melanin is such a protection, and the rate of melanoma is much lower in dark skinned people. There is also a nice correlation ...


30

Vibrio cholerae is known to have two circular chromosomes. Bacteria cell division is a lot simpler and efficient as compared to eukaryotic cell division, partly due in part to the nature of their chromosomes. They don't have to undergo mitosis -- condensation of chromosomes, segregation, spindle fibre formation, attachment et al aren't involved in bacterial ...


30

[G]iven two potatoes, one GMO and one natural, would you be able to detect which is which without having any samples or knowledge about what parts of DNA to consider engineered by humans? No, you can't distinguish them without knowing a priori the DNA sequence of the wildtype and of the GMO. There is no other mark left within a GMO in the general sense. ...


29

TL;DR I'd recommend Population Genetics: A Concise Guide (Gillespie) for an introduction to population/evolutionary genetics. I'd recommend A Biologist's guide to mathematical modelling in evolution and ecology (Otto and Day) if you want to ensure your knowledge in mathematics by learning their application to evolutionary biology. General Entry Books to ...


28

I believe it is for this reason: the female body plan is the default one. Males are a variation upon that, in humans at least. Nipples are part of the basic body plan. For a man to not have them, he would need to actively evolve something that would prevent nipples from developing. There is no selective pressure for the development of such a thing, so it ...


27

Yes, this can happen in non-twins. There is a rare phenomenon that can occur in humans (and some other animals), called 'Superfetation'. This is when some time during pregnancy, a woman has a second oocyte fertilized and implanted. This event is an entirely separate conception, and results in two fetuses of slightly different ages in the womb simultaneously. ...


26

OK, I'll have a go although you really shouldn't combine so many questions into one. 1 The mutation protection "paradox" As already mentioned while many mutations are caught and corrected, not all of them are. You have to consider that a body (the human one, for example) contains several trillion cells, each of which contains 3 billion nucleotides each of ...


25

The first position of the anti-codon, the "Wobble" position, forms hydrogen bonds less well than do the second two. This means that the last position of the codon has less coding potential than the first two. The reason is that the anticodon is at the bottom of the anticodon loop of the tRNA, and so there backbone of the tRNA is bending back to pair with ...


25

In addition to the other answers, let me show you a logical error in your reasoning: Don't we share 50% of our genes with our mother and 50% with our father? You get 50% of our genes from each respective parent (disregarding mutations for now). But if you shared only 50% with each parent, this would imply that your parents don’t share a single gene: But ...


25

The two key concepts here are: sex-specific selection, and the fact that males and females share the majority of genes 1) sex-specific selection Obviously, any population where females lacked nipples would be in trouble. Men, on the other hand, have no evolutionary need for them, but they don't pay much either - there is no strong selection against men ...


25

Here is a tutorial to perfectly understand Hardy-Weinberg Rule! If you feel like you just need a brief reminder, you can skip the text until the section In short... and try out the exercises just to check your understanding. Terms you should know a priori I will not define the following terms, so make sure you understand them locus allele (relative) ...


24

Check out this famous paper by Gould and Lewontin, the Spandrels of San Marco. It's essentially a criticism of your question as it's not really the right question to ask. You're engaging in what they call "adaptive storytelling". The truth is that barring fossil intermediaries it's almost impossible to infer how a species transitioned from primitive ...


24

Actually it is a very important question for laboratory animals (and, I imagine, endangered species) and was calculated to be 25 couples. With any number of animals (including humans), there is always some inbreeding happening, but you can reduce it with the number of breeding pairs and careful pairing. When you get to 25 pairs (50 animals) and have ...


23

The short answer is that corn genome is large and has a huge amount of duplication events. Around 80% of the genome are repeated. It's hard to assemble genomes with large amount of duplications because our sequencing technology, practically, at best can give ~500 base pairs. Figuring out the ordering of duplicated regions relies on scaffold sequences or ...


23

The conservation biology literature has a great deal of information, particularly with reference to developing species survival plans (e.g., Traill et al. [2007] report a minimum effective population size of ~4,000 will give a 99% persistence probability of 40 generations). Because the question specifically mentions human populations, I'll focus my answer ...


23

Diploid organisms, such as we are, generally have two copies of each gene (excepting the sex chromosomes in males). In order to display the genotype for each, geneticists use shorthand. When referring to a gene, + means the wildtype, which is the "normal" version, and - means that the gene is missing, often a knockout. So a typical individual's genome for ...


23

One must always be careful not to stretch an analogy further than it can withstand, but since you started these analogies, I will follow up on them and explain the small mistake you've done in their representations. The two books are not as different as you have in mind. You are not pasting the beginning of Uncle Tom's Cabin with the ending of Harry Potter ...


22

To expand a little bit the other answer, I would also add that bacteria can have other (usually circular) DNA segments aside from their main chromosome. These are called plasmids and are double stranded molecules of DNA that can replicate autonomously. Plasmids often carry genes that allow an organism to survive in certain conditions, for instance they ...


22

I've been doing some reading, and have come up with the following interesting information. Telomeres During cell division the DNA is replicated, but the mechanism is imperfect and in each round of cell division a small section is lost from the end of each chromosome. To compensate and protect the genetic information there are caps – regions of excess ...


22

So, a quick molecular biology lesson. Proteins are the things that make up a good percentage of our cells (which make up a good percentage of us), and are the things that do the work of the cells - many are catalysts and are known as "enzymes". Proteins are encoded by genes - while the statement that one gene codes for one protein is not quite correct (...


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