2
votes
2answers
394 views

How did the first sexual animal come to exist? [closed]

I am more or less familiar with the evolution theory based on mutations. Now, starting with a nonsexual being, how did the first organism that reproduces sexually come to exist.
2
votes
1answer
75 views

How many different smells can a human recognize?

How many different smells can a human recognize? If the space of smells is not discrete, how many dimensions it has (for example, the space of colors is three-dimensional).
2
votes
1answer
66 views

What happens during a Raynauds episode?

Raynaud's phenomenon can be a serious health issue, as the blood flow to the extremities, mainly the fingers is compromised, causing fingers to blanche, and then turn blue. Severe Raynaud's can cause ...
2
votes
3answers
143 views

Why are things conscious?

I've been referred to here from http://philosophy.stackexchange.com/questions/8052/why-are-things-conscious. Could you guys help out? Here's the question: What is the reason for animals or more ...
2
votes
1answer
44 views

How can a respiratory infection lead to a skin infection?

Example of a case: 5 children develop a bright red rash on the face and turns violet after a few days and then disappears. Then maculopapular rash appears on the trunk, buttocks and extremities. It ...
2
votes
1answer
206 views

Is there an “Adam and Eve” for each new trait during (not just human) evolution? [duplicate]

Do new beneficial mutation evolve simultaneously and independently with several individuals of the same specie or only with one specimen who then transfers it to all of the specie? In other words, ...
2
votes
0answers
40 views

How much does a human brain's metabolic rate vary? [duplicate]

Possible Duplicate: How does brain energy consumption depend on mental activity? Our brains consume about 20% of our energy when we're at rest. How variable is a human brain's energy ...
1
vote
1answer
57 views

Modeling intracellular interactions between sender and receiver bacteria

I am involved in a modelling task of a biological process described as follows: -- "Objective: to model behavior of a sender receiver type system The process goes as follows Pre-signal [PS] is in ...
1
vote
1answer
69 views

What is the effect of Montelukast on the amount of IgE in blood?

I know that it decreases the amount of leucotrienes in blood. I saw a patient with high IgE altough under Montelukast medication. This suggests me that Montelukast does not affect the immunoglobulins, ...
1
vote
2answers
118 views

Which was the last significant event in human evolution? What's next?

At 10.000 BC (12 ka), we became the last of the Homo species on Earth. In evolutionary terms this is a very little time range to something happen, but I'm wondering anyway, in this meantime which are ...
1
vote
2answers
92 views

Effect on fitness of mutations

What is the distribution/probability density function (PDF) of impacts on fitness of new mutations? I very welcome any partial answer that does not give the whole PDF but just some information ...
1
vote
1answer
38 views

Dominance/recessivity of new mutations

What is the distribution/probability density function (PDF) of recessivity/dominance of new mutations? I very welcome any partial answer that does not give the whole PDF but just some information ...
1
vote
1answer
92 views

How to relate human metabolic model reactions and cancer drug targets / reactome items?

Trying to find a way to take a cancer drug (from CancerDR, for instance) and infer the metabolic reactions that are affected by it in the Human Metabolic Model. Essentially, I would like to know ...
1
vote
1answer
101 views

Carcinogens, how do they work?

The easiest carcinogenic thing for me to grasp is radiation, as it directly messes with DNA. Then it seems there are other compounds that simply mimic hormones, but these shouldn't necessarily cause ...
1
vote
0answers
112 views

On the definition of gDCW (gram dry cell weight)

I need some clarification on the concept of gram dry cell weight. The unit acronym gDCW stands for gram dry cell weight. My interpretation is that 1 gDCW is equivalent to 1 gram of dry cells, but I ...
1
vote
1answer
1k views

What would be the best design for spike-and-recovery and linearity-of-dilution validation experiments in one 96-well ELISA plate?

I have searched in the web for a detailed explanation of doing such validation experiment, but unfortunately couldn't find a satisfactory one. I came across the following sources: Thermo ...
1
vote
1answer
95 views

How might IVF (and related technologies) alter epigenetic marks?

I was reading up on KCNQ1, which encodes a voltage-gated potassium channel, and I discovered that it happens to be only maternally expressed. This is regulated by KCNQ1OT1, a non-coding RNA, which is ...
1
vote
2answers
362 views

By what mechanism does penicillin resistance usually develop in Streptococcus pneumoniae?

There are three mechanisms: prevention of the interaction between antibiotic and the target PBP; modification of the binding of the antibiotic to the PBP; hydrolysis of the antibiotic by a ...
0
votes
0answers
31 views

Few innervations to blood sugar regulation

Assume you have a case of young female where the intake of 75 grams of pure sugar leads to a rapid peak of blood glucose level (within seconds) plateau phase with very steady blood glucose level ...
0
votes
1answer
58 views

Parallel Autonomic regulation of Cough and Runny Nose

I describe here the serous inflammation of runny nose. Cough is mediated by Cough center. I think Runny nose is also controlled by the autonomic nervous system and probably by some reflex. Assume ...
0
votes
0answers
13 views

To decrease the amount of proteins in the lymphatic drainage for short term

I am looking for some mechanism which can decrease the amount of proteins in the lymphatic drainage only for short term. Assume there is no flow between capillaries and lymphatic system because the ...
0
votes
1answer
15 views

Which ionic channels of Pacemakers can work in very low frequencies in extrasystole?

At frequency 0-3 Hz. Like computer processors which can work at low frequencies and controlling under- and overvoltage. Normal most significant channels are Ca2+ and K+ that are changing. However, I ...
0
votes
0answers
24 views

Laser surgery to stop damaged Sinus node from beating

I am trying to find any publication about laser surgery to stop the damaged sinus node which cannot anymore beat. I could only find publications which modifies SA node function. I am not sure if it ...
0
votes
1answer
34 views

Manifestations of open foramen ovale in adults

I read that foramen ovale opens in 30% of adults. I do not know how much of these openings can then close again. Probably, none. It is not pathogenic if no symptoms. It allows blood to enter from ...
0
votes
0answers
124 views

Genetic Linkage/Mapping question Help

Hello everybody! I need some help with this question in the image posted. As you can see in the instructions, I'm asked to map the genes. So the first thing I did is write out the alleles ...
0
votes
1answer
24 views

To understand clearly extraintestinal diseases

Extradistestinal disease seems to prefer to "bowel" diseases, I think this is about diseases outside gastrointestinal tract so stomach. Consider diseases ulcerative colitis and Crohn's disease ...
0
votes
5answers
273 views

Is evolution true as Darwin said? [closed]

I was telling the theory of evolution to my friends. But they asked me for the proof. They said, we are not seeing any such transition species at present. Neither we have such evidence for evolution. ...
23
votes
4answers
5k views

What does the human body use oxygen for besides the final electron acceptor in the electron transport chain?

My biology teachers never explained why animals need to breathe oxygen, just that we organisms die if we don't get oxygen for too long. Maybe one of them happened to mention that its used to make ATP. ...
22
votes
2answers
8k views

What causes fingerprints to form and why is the pattern formed unique?

I've found research that suggests that the reason we develop fingerprints is because they aid us with feeling surfaces (Scheibert, et al. 2008) and not to increase friction and help with the gripping ...
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 ...
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 ...
15
votes
2answers
2k views

Is there an advantage to linear chromosomes?

The DNA copying enzymes have a hard time working to the end of a chromosome. For circular chromosomes this is not a problem, since there is not a sharp 'end'. However, for a linear chromosome, without ...
14
votes
2answers
155 views

Relationship between our microbiome and personalized nutrition

Recently, it has been asked whether there are 'metabolic types' between humans that can benefit from a sort of personalized nutrition. One answer suggested that one discerning factor could be the ...
14
votes
3answers
3k views

What causes the development of antibiotic-resistant strains of bacteria?

I understand bacteria have become resistant to antibiotics due to selection pressures, but how do resistant bacteria process antibiotics when exposed to it, compared to non-resistant bacteria. Also, ...
13
votes
2answers
920 views

Is the EC50 of an activating protein for an enzyme a good indicator for the binding affinity Kd?

We work with a membrane protein system where measuring the affinity between the enzyme and the upstream activating protein has been difficult, and when measured in detergent solution, it is almost 100 ...
13
votes
1answer
3k views

How does a plant grow before photosynthesis is possible?

During photosynthesis, a plant translates CO2, water and light into O2. I assume the carbon C is further used for the growing process. I wonder how the plant grows before the time where photosynthesis ...
12
votes
3answers
10k views

How many agarose gel bands are typical for circularised DNA

I am aware that circular DNA can be both relaxed and super coiled. However when running an agarose gel of the circular plasmid along with singly digested plasmid with BamHI and HindIII, I see 1 band ...
12
votes
1answer
212 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 ...
11
votes
1answer
784 views

Is there an evolutionary advantage to crying when sad?

It seems as though the act of crying when sad does nothing to relieve that sadness. Is there an advantage to crying from an evolutionary perspective, or is it the end result of a different process? ...
11
votes
4answers
922 views

Has there ever been an attempt to create nutritionally tailored food for adult human consumption?

For all domestic animals, and for all animals kept in laboratory, complete and precise composition of perfect food is figured out (cat food, dog food, cattle, rats, laboratory monkeys and apes) -- ...
11
votes
2answers
335 views

What are the evolutionary niches differentiating an apple from a pear?

So, as far as I understand (basic) evolutionary theories, diversity is generated by "niching." That is, if there is an environmental factor that hasn't been fully used by any species to "profit" off, ...
11
votes
1answer
584 views

How do I get the current “camera position” in PyMol so I can reuse it in scripts?

I have a few protein models I want to take pictures of with various ligands bound. It would be nice if I could do it from the same "position", but the only way I can figure out to repeat the same ...
10
votes
2answers
430 views

Why don't we develop immunity against common cold?

We all suffer from common cold, and that, frequently. Why have we not developed immunity against it till now? By immunity I mean immunity as a species.
10
votes
1answer
143 views

Are there specific conditions that allow humans to see ultraviolet wavelengths

It is fairly common knowledge that the lens in its normal state absorbs ultraviolet (UV) radiation. An interesting notion has come up from time to time in my reading that suggests there are a small ...
10
votes
3answers
355 views

Athletes: nature vs. nurture?

Having watched a lot of olympians the last few weeks, I was struck by how many of them have actually spent their wholes lives/careers training for their one event (be in running a marathon, or ...
10
votes
1answer
516 views

Is there are evolutionary explanation for why humans and primates are ticklish? How might it have evolved?

Tickling is a rather interesting phenomenon: When humans or apes are touched in certain areas like the armpits or sides, we respond with laughter AND frantic attempts to stop the assault. Obviously ...
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 ...
10
votes
1answer
316 views

Can Naegleria fowleri enter through wounds into the bloodstream?

All the sources I've read said that Naegleria fowleri enters the brain through the nose. But lets say that someone had cuts on their arm or leg and they are swimming in water that is conducive to ...
10
votes
1answer
130 views

What portions of the brain have drastic changes in activation when we “sense” someone is there?

I was watching an old Arnold Schwarzenegger movie ("Commando") where he plays an elite soldier (surprise). An enemy tries to sneak up on him, and Arnold says that he smelled the other guy ...
9
votes
3answers
111 views

Standard letter for 5-methylcytosine

I'm working on a piece of software that computes melting temperatures for nucleic acid duplexes, and I'm about to add support for 5-methylcytosine as a nucleotide base. At the moment, the bases ...

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