18
votes
5answers
4k views

Why do the two hemispheres of the brain control the opposite sides of the body?

Why does the left hemisphere control the right and the right hemisphere control the left? I googled it but didn't find a good answer regarding this. Could someone explain? Does this adaptation help ...
18
votes
2answers
1k views

Can rats pass on memories of a maze to their offspring?

A friend of mine told me once about a documentary movie he saw some years ago. On this movie he saw scientists talking about particular experiment. This experiment involved rats and probably ...
18
votes
3answers
1k views

How and where, in the human brain, are memories stored?

Background I am a computer programmer who is fascinated by artificial intelligence and artificial neural networks, and I am becoming more curious about how biological neural networks work. Context ...
18
votes
4answers
1k views

Why do we need red blood cells?

From what I know, the main function of red blood cells is hemoglobin transport. So, why do we need cells packed with hemoglobin: why can't it travel freely in the bloodstream? My own thoughts were: ...
18
votes
2answers
3k views

Do gene expression levels necessarily correspond to levels of protein activation?

I have seen a lot of research into molecular mechanisms of diseases/phenotypes use measures of RNA as a 'proxy' for the level of protein available in the cell. Is this actually valid? My problem ...
18
votes
3answers
263 views

How crowded is the bacterial cell?

I was wondering what is the protein concentration in an E. coli cell. When studying enzyme kinetics and activity in vitro, I would argue that the substrate and enzyme concentrations resemble those in ...
18
votes
2answers
335 views

Can an adult without genetic lactase persistence still develop a tolerance for dairy foods?

While investigating the rise of adult lactose tolerance, I came across the news that China has been encouraging its citizens to drink more milk, even though most of the Asian population lacks the SNP ...
18
votes
1answer
246 views

Is there any convincing evidence for the existence of nanobacteria?

The existence of nanometer scale microorganisms has been proposed and used explain several phenomena including morphological structures in a martian meteorite (ALH 84001) and implication in the ...
18
votes
1answer
20k views

Why is coffee a laxative?

How does caffeine (or any additional agents) act as a laxative when ingested? I'm interested in the metabolic/signaling pathway.
18
votes
1answer
565 views

Do trees age on a microscopic level?

Most animals age via at least two mechinisms: at a "macroscopic" level, basically wear and tear to the point where (on evolutionary time scales) it's more genetically advantageous to optimize for ...
18
votes
1answer
16k views

What is the difference between HPLC and FPLC and why is FPLC preferable for protein purification?

I've used HPLC (high performance liquid chromatography) before (once, so I'm barely even qualified to know what it stands for) so I was surprised when my labmate told me she would be using an ...
18
votes
1answer
468 views

Natural examples of XOR functions at the cellular level

We can often think of cells as a sort of circuit on macromolecules, and can show that they can accurately and robustly implement functions like $\text{MAJ}(x_1,...,x_n)$ (return $1$ if more than half ...
17
votes
4answers
1k views

How to understand influenza strain designations?

What do the strain designations for flu mean? For example avian flu is classified as H5N1, what do the letters H, ...
17
votes
3answers
1k views

How does the immune system “learn” from a vaccine?

According to Wikipedia: A vaccine typically contains an agent that resembles a disease-causing microorganism, and is often made from weakened or killed forms of the microbe, its toxins or one ...
17
votes
2answers
2k views

Why was disease transfer to the Americas one-way?

It is well known that the European colonists brought many infectious diseases to the Americas, and that these had a deadly effect on the native populations, because they had no immunity to them. Were ...
17
votes
2answers
341 views

How does the microbial environment in your gut initiate?

Clearly, a zygote does not harbor any microbes. As it develops, and the alimentary canal tissue is differentiated, I logically assume that there is still no microbial activity in the fetus's gut. I'm ...
17
votes
2answers
272 views

How do fairy rings propagate?

It was somewhat new to me that mushrooms usually aren't individual organisms, but are merely the visible bodies of a bunch of fungi living in the soil. I know that mushrooms emit spores to reproduce, ...
17
votes
1answer
1k views

Is kissing a natural human activity?

The word natural here is meant in contrast to it being a sociological construct. Is kissing in all its forms something natural for humans? Is it instinctively erotic? Or is it just a conventional ...
17
votes
2answers
319 views

What are the major evolutionary pressures for Bioluminescence?

What are the major evolutionary pressures for Bioluminescence?
17
votes
2answers
4k views

What is the mechanism behind “acquired” alcohol tolerance?

I can understand natural variation in alcohol dehydrogenase (ADH) in a population leading to variation in rate of inebriation (after controlling for other variables -- e.g., mass, food consumption, ...
17
votes
4answers
2k views

Why are there exactly four nucleobases in DNA?

Does someone know why DNA is composed of four nucleobases? In particular, is there an explanation for the number? Why four and not two, or eight?
17
votes
1answer
1k views

Do insects' muscles become stronger with exercise?

I am curious to know if insect muscles become stronger with exercise, because I have seen many insects get tired out, but I have never seen one get stronger. They always seem to become permanently ...
17
votes
3answers
200 views

What is the optimal frame size for protein secondary structure prediction methods?

The whole question is What is the optimal frame size for the second and third generation protein secondary structure prediction methods? Justify your answer. I remember it has something to do ...
17
votes
2answers
260 views

How is menstruation not suicide in the wild?

Watch any wilderness special for more than a few minutes, and you'll notice a familiar pattern: when a predator catches the scent of blood on the wind, the hunt is on. Wounded animals make the best ...
17
votes
1answer
213 views

Are there dextral/sinistral higher animals?

For example, almost every dog I've met in my life (more than 20 subjects) uses their right paw touching one while asking for attention. Can it be used as a criterion for calling them dextral? If not, ...
17
votes
1answer
769 views

ATP cost for gene expression

How would you estimate the number of ATPs required to transcribe, export and translate a single eukariotic protein?
17
votes
1answer
628 views

Can siRNA induce DNA methylation in mammalian cells?

Some years ago Hiroaki Kawasaki and Kazunari Taira published an article called "Induction of DNA methylation and gene silencing by short interfering RNAs in human cells" in Nature: In plants, ...
17
votes
3answers
1k views

How long can I store extracted RNA?

If I extract RNA from a (leaf tissue) sample using a one-step phenol:chloroform extraction, how long can those samples be stored at -80°C? And how many times can I defrost and refreeze them before ...
16
votes
3answers
3k views

Were there any flying dinosaurs?

I've seen some articles which came in contradiction with each other. The first article was talking about flying dinosaurs, dinosaurs with feathers and so on. A couple of other articles are talking ...
16
votes
6answers
2k views

Why isn't a virus “alive”?

The recent news about a new supermassive virus being discovered got me thinking. What biological differences between viruses and cellular organisms have made viruses be deemed non-living?
16
votes
3answers
1k views

Do animals exist with an uneven total number of digits?

I recently finished reading Contact by Carl Sagan. In the book they talk about a pattern in the transcendental number like pi or e, and comment that it is found in base 10 or however many fingers the ...
16
votes
2answers
6k views

How do the brain and nerves create electrical pulses?

I have heard that information is sent between the brain and peripheral nerves via electrical pulses or signals, but I don't understand how they create them in the first place.
16
votes
2answers
378 views

Why would diffusion be faster across a non-specialised tissue?

The standard protocol for a person experiencing chest pains is to chew a 300mg aspirin tablet, the argument being that chewing rather than swallowing the tablet results in the aspirin entering the ...
16
votes
5answers
725 views

Pipetting damage on cells

I'm curious how much damage is potentially inflicted by shear stress by pipetting. I know that with syringes for stem cell injection cause a lot of damage. However, to what extend does this happen ...
16
votes
3answers
37k views

What is the difference between orthologs, paralogs and homologs?

These three terms are often misused in the literature. Many researchers seem to treat them as synonyms. So, what is the definition of each of these terms and how do they differ from one another?
16
votes
3answers
895 views

Are single-celled organisms capable of learning?

I've read that the amoeba is capable of learning. Since these protists have no nervous system, it's safe to assume that even highly simplified learning mechanisms of the Aplysia are miles off in the ...
16
votes
7answers
2k views

Is there anything that is completely non-toxic to humans at any dose?

Lately I have seen a number of unrelated "scientific" debates over whether certain substances should be outlawed because they are toxic to humans. My initial, informal reaction is usually to respond ...
16
votes
2answers
4k views

How many humans have been in my lineage? Is it almost the same for every human currently living?

If I were to count my father, my grandfather, my great-grandfather, and so on up till, say chimps, or the most common ancestor, or whatever that suits the more accurate answer, how many humans would ...
16
votes
2answers
234 views

Why is there now only one Salmonella species?

Once upon a time, I chanced upon an old microbiology book that detailed the rather colorful world of enterobacteria. Salmonella in particular stood out, as it seemed there were a lot of species: typhi ...
16
votes
1answer
676 views

Why is the Krebs cycle considered a part of aerobic metabolism if molecular oxygen is not involved in any of the reactions in the cycle

Why is the Krebs cycle considered a part of aerobic metabolism if molecular oxygen is not involved in any of the reactions in the cycle? I originally thought that Krebs cycle was aerobic metabolism ...
16
votes
2answers
1k views

Why is 'Grudger' an evolutionary stable strategy?

I am currently reading 'The Selfish Gene' by Richard Dawkins, which I am sure many here have read. The topic are evolutionary stable strategies (ESS) regarding cooperation. I apologise for the long ...
16
votes
1answer
411 views

What is the lowest pressure at which plants can survive?

What is the lowest pressure at which plants can survive? How the plants behave in a Martian-type atmosphere? Is there any plant that can survive such atmosphere? Can a lichen grow at Martian ...
16
votes
3answers
240 views

What is the reason behind choosing the reporter gene when experimenting on your gene of interest?

I noticed within example experiments in class that different reporter genes are chosen to be inserted near your gene of interest to prove whether or not the gene is being expressed. For example, you ...
16
votes
1answer
2k views

Why do we have five fingers?

Humans (and other humanoid mammals) have five fingers in each hand. Curious to know, why five? Wouldn't more fingers be more useful? Is there any evidence that it used to be different and natural ...
16
votes
4answers
1k views

Why does the cold make us sick?

From the moment we learn to communicate, we always get told, whether by our parents, or our teachers, or by anyone else, to avoid the cold, or to put a jacket on to avoid catching a cold, to dry our ...
16
votes
2answers
5k views

Why is cold water more refreshing than warm water?

Obviously, the temperature of water does not affect its chemical composition. At least not in the ranges we are likely to drink it in. Yet it is clearly far more pleasant and refreshing to drink cool ...
16
votes
1answer
332 views

Why does regular exercise increase brain volume?

It has been shown in several studies that regular aerobic exercise increases brain volume in aging humans. The changes were observed in hippocampus and were correlated with dramatic reduction of ...
16
votes
1answer
326 views

Do marine deep sea life forms exhibit circadian rhythms? If so, what entrains them?

I've been reading a lot about circadian rhythms, when suddenly this question popped into my head: do circadian rhythms exist for deep sea organisms (3000 ft / 1000 meters+)? For land mammals, the ...
15
votes
8answers
8k views

Why have humans evolved much more quickly than other animals?

Humans have, in a relatively short amount of time, evolved from apes on the African plains to upright brainiacs with nukes, computers, and space travel. Meanwhile, a lion is still a lion and a ...
15
votes
3answers
4k views

Why isn't vomit corrosive?

Vomit comes from gastric acid, right? And in gastric acid there is HCl and HCl is corrosive (strong), how come when I vomit, it doesn't destroy things that it (as the vomit) hits (such as floor, ...

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