10
votes
1answer
196 views

What would be the conduction speed of A-alpha fibers, were they unmyelinated?

It's known (Hursh 1939) that myelinated axons exhibit the behavior $v = 6d$, where $v$ is the propagation speed [m/s] and $d$ is the axon diameter [μm]. A related relation for unmyelinated axons is ...
9
votes
1answer
110 views

Are Schwann cells the sole source of myelination in PNS?

Are Schwann cells the only source of myelin for axons in the peripheral nervous system, or are there other neuroglia or other processes that result in myelination of PNS axons?
14
votes
2answers
1k views

What causes REM atonia to be lost in sleepwalking?

I understand that in normal REM sleep the voluntary muscles are in effect paralysed in order to prevent an individual acting out their dreams. This paper indicates that there are likley to be ...
8
votes
1answer
90 views

What are the variables that control/influence the color of oranges(Citrus sinensis)?

I hear that Oranges cultivated in tropical areas of the world tend to be greener when ripe, is that correct? Even the same type of Orange differs in color if cultivated in California or Florida. I ...
7
votes
2answers
204 views

Is “exhaustion” of the Hodgkin-Huxley membrane at constant stimulation a real phenomenon?

I was playing around with a simulation of the Hodgkin-Huxley model using their original parameters for the squid giant axon. By applying a constant stimulation current to the model in resting state, ...
32
votes
4answers
1k views

Can scientists create totally synthetic life?

This particular question has been of a great deal of interest to me, especially since it dives at the heart of abiogenesis.
38
votes
1answer
8k views

Why do Humans not produce Vitamin C like other mammals?

Why do most mammals produce their own Vitamin C? Why do Humans not?
12
votes
1answer
211 views

Abiogenesis: Beyond the research journals as a lead in to discussions on evolution

I just came across this abstract: Aminoacyl-tRNA synthetases (aaRSs) are responsible for creating the pool of correctly charged aminoacyl-tRNAs that are necessary for the translation of genetic ...
6
votes
3answers
276 views

Where can I find the common names for the zoology taxonomy?

Forgive me if my question does not belong here or if I'm using incorrect terms, but I'm not educated in biology at all. I'm investigating the workings of the biological classification system. I was ...
11
votes
1answer
450 views

How do CpG islands remain unmethylated?

In most of the genome CpG sites are pretty much always methylated, but CpG islands are instead often unmethylated. This has been linked to the fact that they often are associated to transcripted ...
13
votes
1answer
8k views

What effect has changing pH and salt concentration on protein complexes?

I'm struggling to find peer reviewed literature that explains the effect of changing the pH and the salt concentration on protein/protein complexes in solution. What effect does the pH and the salt ...
12
votes
4answers
298 views

Online repositories of scanning electron microscope photographs?

I have looked at every single Wikimedia commons photo in the category 'scanning electron microscope'. Unfortunately, I could not find any other repositories of such photos, but I would readily look at ...
7
votes
1answer
162 views

Can oxygen diffuse out through the lungs?

Let's say you accidentally walk into a room pressurized with pure nitrogen (or you're jettisoned into space). Within a couple of seconds, the partial pressure of oxygen within your lungs drops to 0. ...
25
votes
7answers
418 views

Has there been any observation of species adapting the evolution process?

I am very interested in the evolution of the evolution process itself. There are of course a lot of things that influence how evolution will work, but for this question, I am interested in things that ...
10
votes
1answer
132 views

Are these Gram stain substitutions acceptable?

In the context of a Gram stain on a blood smear: Are the following acceptable substitutions and/or what differences could arise by substituting them? Using methylene blue instead of crystal violet ...
11
votes
1answer
147 views

Is Batesian Mimicry a form a parasitism? To what extent is the species with real defenses harmed by the defenceless species?

It seems like Müllerian mimicry would be an example of mutualism because both species would end up being eaten less by predators that only have to learn one pattern of warning symbols. But to what ...
17
votes
2answers
465 views

How is temperature sensed?

Can anyone summarize the mechanism by which when an object of a given temperature is placed in contact with, say, the skin on a human fingertip, the average speed of the particles of the object is ...
3
votes
1answer
72 views

Is there a photobleaching-resistant, cell-permeant viability stain in the far red part of the spectrum?

I am looking for a live-cell–impermeable dye for viability. (The cells cannot be permeabilized and fixed in this experiment.) I would prefer with excitation and emission spectra similar to Cy5, but I ...
9
votes
1answer
579 views

Is trembling an advantageous response during periods of anxiety?

I originally had planned to ask about whether there was any biological truth in the popular phrase "shivering with fright". However, after doing a fair bit of googling it seems that there is a lot ...
16
votes
2answers
354 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 ...
24
votes
5answers
779 views

Why do we age? or Do we have a theory of senescence?

There seem to be a number of ideas about why we age. Hypotheses include the gradual accumulation of cell metabolic products affecting organism function and the reduction of telomere length during cell ...
9
votes
1answer
102 views

What is the base cancer rate for an arbitrary carcinogen?

Are all carcinogens equally potent? Is the relationship between dose and probability of cancer roughly equal, or are there some carcinogens that provoke cancer significantly more than their cousins?
26
votes
2answers
486 views

Is there evidence that some non-human species perform sexual selection based primarily on intelligence? How do they do this?

I'm a biology amateur, but it seems like sexual selection is almost always performed based on physical characteristics, the outcome of physical contests, or some sort elaborate courtship. But do any ...
8
votes
1answer
323 views

Coincidence that navel is near the womb?

The attachment point of the umbilical cord in a baby girl is very close to where her own baby would develop. Is there something in the evolutionary history of mammals that explains this, or some ...
9
votes
1answer
581 views

Why are there nail growth differences between humans and other mammals?

When a cat is growing, his nails are growing with him to some extent. A grown cat has a fixed nail length that is not extending. By contrast, human finger nails just keep on growing, so we have to ...
15
votes
6answers
905 views

Could Junk DNA be used as a Turing Machine by nature?

In what ways has DNA been studied to see if there a "programmable" aspect to it? Has nature produced anything resembling a Turing machine within the cell, perhaps using the "junk DNA" as its code? I ...
46
votes
3answers
2k views

Why did the process of sleep evolve in many animals? What is its evolutionary advantage?

The process of sleep seems to be very disadvantageous to an organism as it is extremely vulnerable to predation for several hours at a time. Why is sleep necessary in so many animals? What advantage ...
13
votes
2answers
328 views

Why was it so hard to decode the corn genome?

My teachers growing up told me it was impossible to decode the maize genome. But yet its been done. Why was decoding the genome so significant, and what made it so difficult?
8
votes
1answer
2k views

Effects of Polyphasic vs Monophasic sleep in humans

Why do humans practice monophasic sleep cycles? When altering one's circadian rhythm to a Polyphasic sleep schedule, how much would that affect development? Is Monophasic sleep (once per day) ...
10
votes
2answers
763 views

Why are restriction enzymes not frozen?

We all know restriction enzymes are proteins, but we never freeze them. They are instead provided in high glycerol containing solutions by companies and stored at -20C. Is there a reason why this is ...
13
votes
3answers
716 views

How many human proteins have a solved 3D structure?

I was wondering how many human proteins have a solved 3D structure. Is there a database with only human proteins? I looked at pdb but couldn't find a filter.
19
votes
2answers
418 views

Smallest viable reproducing population

What is the smallest viable reproducing population, such as in a human population. By viable I mean a population which keeps genetic defects low (enough). A very strongly related question: what is ...
14
votes
3answers
520 views

What is the most difficult feature to explain evolutionarily? [closed]

I wonder what are examples of organs/structures/behaviours/cooperation that evolutionary biologists themselves find most difficult to explain -- to explain how they could appear evolutionarily -- ...
7
votes
1answer
349 views

To understand why satellite cells are genetically inactive in Barr body

DAPI is used as a stain for DNA heterochromatic and euchromatic regions. The Barr body is heterochromatic. In the slide of a normal human female cheek's somatic cells, there is apparently no other ...
7
votes
1answer
749 views

What do the variants on the PolyT sequence mean?

My son has been diagnosed with Cystic Fibrosis. I am not looking for medical advice regarding his condition, but I am very interested in understanding the genetic causes of his condition. In ...
2
votes
2answers
2k views

What is the Giemsa staining of chromosomes?

I got the question in my exam and wrote the following and I do not understand what is wrong in it: Giemsa staining is a staining method to stain particularly malaria and other parasital diseases. ...
9
votes
1answer
91 views

Time from stimulus to gene expression

My understanding is that gene expression, in response to some stimulus, generally occurs on the order of minutes. I'm curious about the extremes...the quickest and the slowest cases. What is(are) the ...
13
votes
3answers
1k views

What implications has the missing 2'-OH on the capability of DNA to form 3D structures?

The chemical difference between RNA and DNA is the missing 2'-hydroxyl group in the nucleotides that build DNA. The major effect of that change that I know of is the higher stability of DNA compared ...
7
votes
2answers
469 views

How can I measure bacterial alkaline phosphatase activity?

I want to measure alkaline phosphatase activity using PNPP in my mutant bacteria strains, but all the protocols I found involve purification of the phosphatase (which I have no need of). Does anyone ...
3
votes
1answer
103 views

Are ectopic beats considered sinus rhythm for pNN50 purposes?

One quantification of the heart rate variability of an ECG is pNNx, i.e. the proportion of consecutive NN distances that differ by at least 50 ms. When a premature beat occurs, the preceding and ...
7
votes
3answers
162 views

Alternate genetic codes in newly sequenced organisms

Variations of the standard genetic code are pretty rare, but as the cost of high-throughput genome sequencing continues to drop, there is a greater possibility of discovering additional exceptions. ...
5
votes
3answers
1k views

How do you break up cell clumps when passaging?

I am working with HepG2 cells, and they really like to form clumps. Pipetting up and down in TrypLE does not seem to be very effective in breaking them up.
4
votes
1answer
149 views

Is a raised baseline between T and QRS normal in any ECG lead?

Here are excerpts from an unknown ECG lead. I find it weird that the "baseline" changes after the T wave and doesn't return until after the following QRS complex. Is that normal/expected for any lead? ...
15
votes
3answers
257 views

Defining paper(s) in epigenetics

For someone who is interested in learning about the discovery of epigenetics, which are the foundational defining papers in the area?
14
votes
6answers
1k views

Online Molecular and Cellular Biology Video Lectures?

I am looking for video lectures to go through to guide my reading in intro molecular and cellular biology. I've had intro bio and I study evolutionary theory, but my molecule- and cell-level knowledge ...
8
votes
1answer
86 views

Which aspects of renal physiology are standing in the way of an artificial (mechanical) kidney?

Scientists have been able to create artificial organs with varying degrees of success. The mechanical heart (in its various forms, e.g. ventricular assist) is able to sustain life for some period of ...
30
votes
4answers
706 views

How does the sensitive plant detect vibrations?

The sensitive plant (Mimosa pudica) is a remarkable little plant whose characteristic feature is its ability to droop its leaves when disturbed: Apparently, this ability to droop rests on the cells ...
9
votes
1answer
100 views

Last-ditch efforts to maintain thermal homeostasis

I was in the gym's steam-room today and a thought occurred to me: have I truly thwarted all possible mechanisms for maintaining thermal homeostasis? There's sweating, which is thwarted because the ...
12
votes
1answer
587 views

How many people's DNA were involved in the compilation of the reference human genome?

I know that the reference human genome is complied from DNA portions from different people, most of whom were European. Do you know how many of them were involved? Do you know which ones were ...
42
votes
2answers
1k views

Is there any evidence that sexual selection may lead to extinction of species?

Darwin suggested that sexual selection, especially by female choice, may counter natural selection. Theoretical models, such as a Fisherian runaway process, suggest that evolution of preference and ...

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