6
votes
2answers
221 views

How do infectious bacteria know when their numbers are high enough to attack a host?

When you get sick, you generally don't contract enough bacteria at once for them to succeed in battling your immune system, right? Their numbers must gradually increase in the host's body before they ...
5
votes
1answer
255 views

Is there a practical upper limit to amount of nucleotides or genes in a transformed plasmid?

I'm currently working on a synthetic biology project which involves working with lots of different parts. I would ultimately like to integrate these genes by transforming a single plasmid. I've heard ...
9
votes
2answers
447 views

Does arterial blood always flow away from the heart?

Is there a negative net flow of blood in human arteries at any point of the cardiac cycle? I realise that blood flow can be turbulent, e.g. in the aorta or around stenotic arteries, but then the ...
4
votes
1answer
449 views

Meat and mushroom allergies, why are they so rare?

There are a lot of food allergies, but for some reason not to meat (mammalian meat or poultry) or mushrooms. I've googled a bit, and now I know that one can actually have a meat or mushroom allergy, ...
2
votes
1answer
130 views

Why is elevated homocysteine considered a risk factor for angina?

Elevated homocysteine levels are listed among risk factors for angina. How is homocysteine related to the heart? Or the coronary arteries? How do these relationships make it a risk factor for angina? ...
9
votes
1answer
148 views

Protein data bank syntax: Can two protein secondary structures “overlap”?

I have a technical question regarding the syntax in Protein Data Bank files. In the protein with PDB# 1AE9 (pdb file), there are two lines in the .pdb file: ...
2
votes
1answer
732 views

Ammonia smell after physical exercise? What is the explanation? [duplicate]

After exercising vigorously one can sometimes smell ammonia and it feels like it's coming from within the nose actually. There is no indication that others can smell it when I do (i.e. seems to be ...
4
votes
1answer
372 views

What causes instinctive behaviour?

Some actions, almost behaviour, exist that are common across a species. For instance, based on personal observation, human babies try to taste anything new they encounter until they are a few score ...
6
votes
2answers
23k views

What is the function of the RNA primer in DNA replication?

During DNA replication, RNA primase puts an RNA primer in the lagging strand. What is the function of this RNA primer? Why can't the enzymes put DNA fragments directly?
3
votes
2answers
734 views

Does finite rate of increase depend on mortality of individuals in a population?

As written in my lecture handouts, there two main factors in the Geometric Growth Model of populations: $R_{0}$ is the expected lifetime reproductive output. This way, for unicellulars, for example, ...
6
votes
1answer
552 views

What happens to an ant colony when the queen dies?

Does the colony collapse? Do workers keep following the last orders? Or can future queens replace the dead one? I'm guessing this might also depend on each specific sub-species.
2
votes
1answer
117 views

What kind of mushroom(?) is this?

I found groups of these growing in the Lassen National Forest (Susanville, CA, USA). It looks like some sort of mushroom. I have Googled extensively, but can't seem to find a match.
2
votes
0answers
58 views

Why do conker flowers grow upwards?

Most trees I know that have their flowers in groups hang these groups down. I noticed, however, that conker flowers grow upwards! I guess that growing against gravity requires special effort, so ...
3
votes
1answer
1k views

How do liver and lung metastases cause death?

Metastasis to the liver and lungs are the main causes of death in colorectal cancer.(1) I understand that colorectal cancer may have metastases. But how do these metastases cause death? Reference ...
6
votes
1answer
139 views

Why does getting certain chemicals in cuts hurt?

More specifically, shampoo. What are the mechanics of detecting a noxious chemical stimulus in terms of which receptors recognise what, how do they do it, and how is this information relayed to the ...
8
votes
2answers
110 views

Where can I find historical data on world-wide ecology parameters?

I hope this is the right StackExchange forum for such a question. I'm looking for large data sets on world-wide ecology parameters, such as annual temperatures by latitude, annual rainfall, CO₂ and ...
5
votes
2answers
327 views

What medical and commercial proteins are made using genetically modified animals?

Recombinant technologies in micro-organisms being used to produce commercial and medically useful proteins like insulin are fairly common. However some proteins are still produced commercially in ...
5
votes
1answer
273 views

Experimental evidence for the selfish gene vs. the selfish individual

In the Selfish Gene, Dawkins makes the argument that a better view of evolution (i.e. more in accordance with experiment) is obtained if you view the basic unit of evolution to be the gene rather ...
7
votes
4answers
331 views

Can sexual reproduction create new genetic information?

Is there a small chance that in sexual reproduction a new allele forms in the off-spring that was not present in either of the parents, or are the alleles in the offspring always from at least one of ...
1
vote
1answer
32 views

cell uptake prediction

I'm generating random molecules I would like to know if they are able to pass through the cell membrane. Are there any ways (preferably computational) to predict cellular uptake of an organic molecule ...
9
votes
2answers
401 views

Is there any recent evidence for the aquatic ape theory of human evolution?

aquatic ape theory suggests that many features that distinguish humans from their nearest evolutionary relatives emerged because the ancestors of humans underwent a period when they were adapting to ...
7
votes
1answer
204 views

Why are some menstrual cycles irregular?

A friend of mine asked me this today, and I didn't know. I remember studying the menstrual cycle a few years ago, but I can't remember the details (other than it was very hormone-related), and so I ...
1
vote
0answers
221 views

Does brain activity generate heat gradients in the brain?

I'm reading this article on guiding axon growth using temperature gradient, and it mentions that the trajectory of growth of neuron connections can be influenced by temperature gradients as little as ...
4
votes
1answer
649 views

How do I view the simulated protein structure along with ligand in VMD?

I did a simulation of a protein-ligand complex, and it has stabilized after 5 ns. I have got the respective pdb files for every ns, but when I try to view in VMD (Visual Molecular Dynamics), I cannot ...
1
vote
1answer
42 views

In vitro enzyme production

I need to express a protein in vitro but I don't know where to start. I will likely do a T7 transcription protocol but for translation I am not sure what to do. Are there any good kits?
2
votes
1answer
836 views

Do male marsupials have a pouch?

Do male marsupials have a pouch, or is it a female organ only (like the womb)?
2
votes
1answer
181 views

What is this marmot-like animal (Tigray, Ethiopia)?

I was searching what are the animals I frequently saw in the north of Ethiopia. I took some bad quality pictures. For me it looked like a large squirrel, local people called it a rat, and on the ...
5
votes
1answer
173 views

What effect do oligosaccharides, like those found in legumes, have on the composition of intestinal flora in humans and if so how so?

I know that intestinal flora metabolising oligosaccharides, like those found in legumes, is the cause for the well known fact that legumes cause flatulence, but does an oligosaccharide-rich intestine ...
1
vote
2answers
214 views

Has medical progress stopped human evolution? [duplicate]

We can cure many diseases nowadays, and thus the natural selection is very limited. Plus, mankind spent the whole beginning of its existence in almost the same hostile environment, and that's where he ...
0
votes
1answer
34 views

First genomic survey of human skin fungal diversity

"The researchers found that a single type of fungus, belonging to the genus Malassezia, is predominant on the head and trunk. Hands, which harbor a great diversity of bacteria, are home for relatively ...
2
votes
1answer
56 views

What does “rapamycin-sensitive oncogenic transformation” mean?

Can someone explain exactly what "rapamycin-sensitive oncogenic transformation" is? I get that it's a drug that suppresses the immune system but what does it have to do with oncogenic transformation? ...
4
votes
1answer
145 views

Is Active Transport Required For Life?

Is active transport required for all living cells to function? I was under the impression that if a cell doesn't have active transport, it either would lose molecules through the membrane and not be ...
6
votes
2answers
312 views

Intrinsic apoptosis in erythrocytes

With a lack of mitochondria, can red blood cells perform intrinsic apoptosis and do they have another way of generating cytochrome c to attach to a CARD domain and assemble the apoptosome? Or are ...
3
votes
2answers
232 views

How does the immune system distinguish own and foreign antibodies?

Therapeutic antibodies, for example Rituximab which recognises CD20 on B lymphoma cells, can cause adverse effects (e.g. http://www.ncbi.nlm.nih.gov/pubmed/19399690) One reason behind these adverse ...
2
votes
2answers
480 views

Why is a slow worm not considered a snake?

Slow worms are considered lizards as opposed to snakes, both are reptiles. Now I get that there are traits that distinguish them (eye lids, ears ...). But snake species themselves vary already quite a ...
6
votes
1answer
656 views

Cat purring: What are some possible underlying mechanisms behind purring and bone remodeling and formation?

http://www.scientificamerican.com/article.cfm?id=why-do-cats-purr The article above says that cats purr mostly when they're wounded or under duress. They hypothesis that cats purring leads to ...
1
vote
1answer
110 views

copper spiral birth control not toxic?

I Always thought that copper was toxic to the human body. So how can it be safe to place a copper object (birth control spiral) into a uterus for a duration of 5 years?
0
votes
1answer
196 views

Excretion and metabolic waste?

I know there is a difference between digestive and metabolic waste, but which one is called excretion? And what's the other one called? Thanks!
5
votes
1answer
423 views

What could account for an apparent loss of mass at death?

An interesting tidbit floating around the internet these days is that Dr. Duncan MacDougall apparently weighed people shortly before and after death, and found an average of a 21 gram discrepancy, to ...
10
votes
3answers
2k views

DNA synthesis companies: cost per base, turn-around time, codon-optimization algorithms

I would like to synthesize a 3.4kb gene (originally isolated from soil bacteria) and transform it into E. coli. There are several companies (DNA2.0, GeneScript, BlueHeron) which will synthesize the ...
1
vote
1answer
57 views

What's food mode?

I've been watching a The Crocodile Hunter episode about Komodo dragons, and Steve Irwing kept speaking about the animals being in "food mode", in which they apparently change their behavior to one of ...
2
votes
1answer
42 views

Range of feasible coefficients in an unlimited growth model

If you are given an unlimited growth model in the form: $\frac {dP(t)}{dt} = k P(t)$ Obviously the population growth would never be unlimited, but let's presume for the moment that we are ...
2
votes
2answers
48 views

Can stress echocardiography show coronary blood flow difference before and after exercise?

Stress echocardiography means a pair of cardiac ultrasound imaging examinations, before and after exercise. I assume that coronary blood flow is increased after exercise. Is cardiac ultrasound ...
1
vote
0answers
60 views

Reverse complement of reconstruction model for assembling reads

One way to assemble fragments produced by DNA sequencing (often called reads) is to seek for the shortest common superstring that contains all the reads of a given set of reads. One model for this ...
1
vote
1answer
36 views

Transplantation of stem cells

During the autologous transplantation of stems cells from bone marrow to produce new blood cells why all the other stem cells other than the one obtained are destroyed?
4
votes
1answer
50 views

Immunity during pregnancy

I have learnt that our immune system distinguishes self from non-self by using MHC. So a mother during pregnancy should also develop antibodies against the fetus as it is also a genetically different ...
1
vote
3answers
386 views

Diffusion across cell membranes

I got this question and don't really understand the difference between the answers. Diffusion is (in cell membrane): a) passive by nature, no metabolic energy is needed b) driven process by ...
3
votes
3answers
1k views

Knockdown of long noncoding RNA (lncRNA) - how is it done?

I don't work at the wet lab and don't know all the details about the knockdown techniques. My question is: How lncRNA knockdown is done? For example - you have lncRNA that is functional in the ...
2
votes
0answers
51 views

How to use mechanical microstrainer to extract tissue proteins from human? [closed]

Background: There are many methods to extract proteins form human tissues out there. The majority of them use an extraction buffer containing variable concentrations of detergents and protease ...
5
votes
3answers
360 views

Tool for nucleotide alignment with all nucleotide codes (e.g. R, Y, W, S, etc.)?

I have a vector sequence and would like to find the following nucleotide sequence in it. AASYWSRA This query sequence uses several degenerate symbols, defined ...

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