20
votes
2answers
1k views

How does RNA transcription determine which half of the DNA to use?

I feel that I might have a complete misunderstanding here. If DNA has two strands, how does the machinery of RNA transcription determine which one to transcribe?
20
votes
3answers
2k views

Why is high fructose corn syrup unhealthy?

I understand that high fructose corn syrup was found to have detrimental effects on peoples' health. Why is this so?
20
votes
3answers
470 views

Good source that explains the evolution of single-celled organisms “from scratch”

Are there any books or sites that detail, step-by-step, the evolution of the first single-celled organisms (bacteria, archaea) from a Miller-Urey-like beginning? That is, assumes only amino acids, ...
20
votes
2answers
372 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 ...
20
votes
3answers
998 views

How is RNAse contamination in RNA based experiments prevented?

Does anyone have any suggestions to prevent RNAse contamination when working with RNA? I tend to have issues with degradation regardless of whether I use DEPC treated / RNAse free water and filtered ...
20
votes
4answers
4k views

Where does the 'C' in exhaled CO₂ mostly come from?

When a human being exhales CO₂, what is, by the numbers, the main source of carbon atoms exiting the body in this way? I mean what class of cells, or which tissues are the biggest on a pie chart of ...
20
votes
1answer
3k views

Why is water flavorless?

I read recently that humans have an innate preference for sweet-tasting foods. That seems feasible since carbohydrates are necessary for cells to undergo cellular respiration, but why then is water ...
20
votes
3answers
62k views

Why can white hairs get dark again?

I have learned (probably in high school?) that hairs turning white is caused by the part of the folicle which produces the pigment dying and being replaced by an air bubble. This sounds very ...
20
votes
1answer
263 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 ...
20
votes
1answer
23k 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.
20
votes
1answer
4k 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 ...
20
votes
2answers
161 views

How is duration of efficacy estimated for vaccines?

Vaccines, especially those given in adulthood, usually have term limits attached, eg: 10 years for yellow fever or 3 years for typhoid. Since presumably the time course of an immune response is no ...
20
votes
1answer
637 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 ...
20
votes
1answer
532 views

Why are many fruits sour?

Many fruits (like apples, berries, citrus fruits etc.) contain high levels of organic acids, especially malic acid and citric acid. Are there any evolutionary functions of those acids in ripe fruits? ...
20
votes
1answer
347 views

Evolutionary origin and exogenous cues of ~28 day infradian rhythm?

The most obvious example of an approximately monthly biological cycle is the human menstrual cycle. My questions are the following: Is it known when and where this cycle or one like it arose? What ...
20
votes
1answer
279 views

Can someone identify this ant?

This is one of seven ant queens I just collected yesterday morning (2015-09-21 9AM) around home. I live in Hong Kong, at a hillside facing south. The weather was as follows (Hong Kong Observatory ...
19
votes
5answers
9k views

Why haven't prey evolved the ability to always outrun their predators?

I can understand why some prey can't outrun a recently evolved species. However, since cheetahs have existed for so long, why haven't its prey evolved to always outrun it, driving cheetahs to ...
19
votes
5answers
2k views

How can homosexuality evolve despite natural selection?

I would imagine that the answer to this question would be population control, especially since even if one sibling is homosexual this does not necessarily mean that the other siblings will be too.
19
votes
4answers
3k 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 ...
19
votes
2answers
1k views

Do plant-animal cross races exist?

Plants and animals have the following distinct properties: Plants live from solar energy by photosynthesis, they use solar energy to make sugar and oxygen out of carbon dioxide, which gives them ...
19
votes
5answers
2k 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 ...
19
votes
4answers
5k views

Why do parasites sometimes kill their hosts?

It's bothered me for a while now. I understand why a parasitoid would do this, as it only temporarily requires the host, and that not all parasites kill their hosts. There seems to be no evolutionary ...
19
votes
3answers
80k views

NADH vs. NADPH: Where is each one used and why that instead of the other?

I know NADH is used in cellular respiration and NADPH is used in photosynthesis. What difference does the phosphate group make that the same one isn't or can't be used for both? Is there a greater ...
19
votes
2answers
374 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 ...
19
votes
1answer
3k views

What is the speed of blood?

The speed of blood may vary from one place to another and may be quite low in the tinyest vessels compared to the biggest one. What is the speed of blood while exiting a normal human heart?
19
votes
1answer
26k 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 ...
19
votes
1answer
868 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 ...
19
votes
4answers
1k views

Why do we laugh?

Why is it that the reaction we get from absurdity is laughter? Everyone does it, even babies. Is there a reason why it is our instinct to laugh when we see or hear something absurd/humorous
19
votes
1answer
1k views

Can beavers control the direction a tree falls?

We humans can easily control the direction a tree falls by making a number of strategic cuts, essentially creating a hinge: This prevents trees from falling on equipment and people and sets them up ...
19
votes
1answer
1k views

ATP cost for gene expression

How would you estimate the number of ATPs required to transcribe, export and translate a single eukariotic protein?
19
votes
1answer
272 views

Why do you die if you cannot breathe?

I was wondering what the actual reason for death by suffocation is. Obviously it is related to oxygen deprivation. But what is the underlying cause of death? Is it due to insufficient oxygen for ...
19
votes
3answers
2k 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 ...
19
votes
1answer
189 views

What is the mechanism responsible for the periodicity of hiccups?

Hiccups (singultus) are caused by involuntary spasm of the intercostal muscles and diaphragm, producing a sudden inspiration with associated glottic closure. It seems the neurobiology of the reflex ...
18
votes
6answers
2k views

Human evolution: Where *exactly* did the first human come from, whose parents were not?

Layman here. So I have never really quite understood this facet of human evolution, (or any other for that matter), in that, I understand the evolutionary process, but I get lost on the 'border' ...
18
votes
2answers
2k views

Can Biologists identify all viruses?

I went to the doctor today with my girlfriend, and the doctor said that she had a virus but doesn't know which one and she should let the infection heal with some rest. The fact that the doctor ...
18
votes
4answers
5k views

Are mitochondria dead?

In the video "What is Life? Is Death Real?", the subject of mitochondria is raised at 2:58. At 3:12, the narrator says "[mitochondria] are not alive any more: they are dead." What currents of thought ...
18
votes
3answers
15k views

Do cows produce milk excessively?

Do cows produce more milk than it is required for their calves? It seems like cows are able to provide milk all the time (all year around). Is it so? Or do they, like other mammals, produce milk only ...
18
votes
2answers
2k views

Could viruses be used as antibiotics?

Could we use viruses that only affect bacteria to act as antibiotics? The more bacteria, the more times the virus divides, so the stronger it gets. Is this practical?
18
votes
2answers
3k views

Harmless virus?

Is it possible for a virus to live symbiotically with its host? Is the human body plagued with viral infections that do negligible harm, or even serve a beneficial role?
18
votes
3answers
520 views

Are human fetuses more likely to be male? [duplicate]

Question: From a physiological point of view, when sex is determined in a human fetus, is it equally likely to be male or female? Studies in this area typically measure age at birth, where the data ...
18
votes
2answers
2k views

Is it known how the first viruses formed?

The oldest known virus is known to have infected prehistoric insects 300 million years ago. A virus is basically a parasitic strand if DNA or RNA encapsulated in a protein coat. It enters cells by ...
18
votes
2answers
3k views

How can birds disperse seeds when they are able to digest them?

I've just read in a book that birds' guts can digest almost all the consumed seeds with the exception of mistletoe and loranthus (which stays stuck on the branches). On the other hand, I know that the ...
18
votes
1answer
876 views

Why can't I read everything in my field of view?

When I look at a piece of text, I can see all the text on the paper, no matter where I look, because my field of view covers it all. However, if I stare at a specific word, I cannot read the text a ...
18
votes
2answers
323 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, ...
18
votes
2answers
2k views

Is any known plant magnetic?

Is there a plant (not a microscopic type but one that is visible to the naked eye) that has so much iron (or magnetite), cobalt, or nickel in its body that it can attract a magnet? In this case ...
18
votes
2answers
388 views

What are the major evolutionary pressures for Bioluminescence?

What are the major evolutionary pressures for Bioluminescence?
18
votes
2answers
47k views

How many human cells are there in our body, on average?

How many human cells are there in our body, on average? Wikipedia says 1013: Bacterial cells are much smaller than human cells, and there are at least ten times as many bacteria as human cells in ...
18
votes
4answers
5k 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?
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
1answer
3k 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 ...

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