All Questions
5
votes
1answer
117 views
Can you consider a human as alive, or is it the cells on the body that are alive?
Sorry if this question seems strange, but in the recent time I have been interested in the question of what life is and how you can define life.
My question:
How long can individual cells live on a ...
5
votes
1answer
145 views
Computational/mathematical models for predicting phenotype from genotype
Karr, Sanghvi, et al. (2012) propose a whole-cell computational model for predicting phenotype from genotype in Mycoplasma genitalium. Their model simulates myriad cell processes such as DNA ...
4
votes
1answer
83 views
What is a Mitochondrial Eve and Y-chromosomal Adam
I've read this question:
What kind of event would cause the current Mitochondrial Eve to be replaced by a new one?
And the values in Wikipedia about Mitochondrial Eve and Y-chromosomal Adam and I am ...
4
votes
2answers
117 views
Extraretinal photoreception in mammals? [duplicate]
A Finnish firm Valkee sells light-ear-plugs against thing such as jetlag. I asked a researcher in Aalto university how do they really work and he responded ...
4
votes
2answers
470 views
Why does alcohol cause the hemolysis of RBC in a large proportion?
I had today an experiment that we put 95% alcohol to the blood which made it completely transparent so hemolysis must have occurred.
I started to think about the reasons.
I think that this is because ...
4
votes
0answers
44 views
What light intensity determines the start/end of a photoperiod in humans?
I'm reading this article, which discusses the influence of Long Photoperiod (LP) and Short Photoperiod (SP) on melatonin production:
HIOMT drives the photoperiodic changes in the amplitude of the ...
4
votes
1answer
101 views
Are there any effects of elevated Cysteine levels on cognitive function?
I'm looking at this diagram of homocysteine metabolism and see two distinct pathways that the amino acid may get metabolized to: with vitamin B12 it gets converted back into methionine, while with B6 ...
4
votes
1answer
660 views
How does this illusion work?
I found this image on Google+
If you shake your head you can see a portrait of a person. Can anyone explain how the image is constructed in the brain?
3
votes
0answers
84 views
If D1 receptors stimulate adenylate cyclase (through GPCRs) and D2 receptors inhibit it, then why do mutations in both have similar effects?
D1 and D2 both refer to specific types of dopamine receptors.
I'm sure it has something to do with the fact that the D1 receptors are in regions different from D2 receptors.
I know that adenylate ...
2
votes
0answers
37 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
46 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
68 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 ...
22
votes
3answers
2k views
Why do eukaryotic organisms have introns in their DNA?
We touched on introns and exons in my bio class, but unfortunately we didn't really talk about why Eukaryotes have introns. It would seem they would have to have some purpose since prokaryotes do not ...
20
votes
4answers
511 views
Why do men have nipples?
I'd be tempted to call nipples in men vestigial, but that suggests they have no modern function. They do have a function, of course, but only in women. So why do men (and all male mammals) have them?
...
16
votes
1answer
1k views
How does laughing gas (N2O) work?
Laughing gas (N2O), well, makes people laugh.
How does just a gas make us do that, there has to be some hormones at work...
So, I wanted to know how this works? What is the mechanism?
16
votes
2answers
232 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 ...
15
votes
4answers
698 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?
15
votes
2answers
390 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 ...
15
votes
3answers
285 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 ...
14
votes
1answer
630 views
Why do we get runny noses in the cold?
The most annoying thing for me about being cold is a runny nose. Is there an advantage to having a runny nose when cold? What does having a runny nose achieve?
14
votes
1answer
115 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, ...
13
votes
2answers
441 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 ...
12
votes
2answers
407 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 ...
12
votes
3answers
2k 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 ...
11
votes
1answer
391 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 ...
11
votes
1answer
775 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 ...
11
votes
1answer
179 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 ...
10
votes
3answers
255 views
Where does the 'C' in exhaled CO2 mostly come from?
When a human being exhales $CO_2$, 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 ...
10
votes
1answer
335 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? ...
10
votes
1answer
190 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 ...
9
votes
1answer
608 views
How does translational coupling work in prokaryotes?
Today I heard about a phenomenon called "translational coupling", where the translation of one protein influences the translation of another protein. The messenger RNA levels don't seem influenced. ...
9
votes
3answers
251 views
Source of DNA sequences
I'm working on a project where I am taking DNA sequences and translating the codons into musical notes. I have some good ideas of how to do this, I'm just not sure what sequences to work with. My case ...
9
votes
4answers
158 views
What was the reason for some plant and animals to become giant in course of evolution?
The dinosaurs, mammoths, giant plants etc are known to be bigger than modern animals. I wonder why they had been lived and why they are not living now? I really don't know much but is it something ...
9
votes
1answer
415 views
What's the effect of oxygen deficit on plants?
As I know all cells require oxygen. So my question is how efficiently can plants operate in no-oxygen atmosphere? Do all plants produce enough oxygen for themselves? Can they consume their own oxygen ...
9
votes
1answer
129 views
How does herpes (HSV) infection suppress HIV?
HIV compromises the human body to defend against infection. Yet people who are infected with herpes are at less risk of developing AIDS.
How does this work?
9
votes
1answer
157 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 ...
9
votes
2answers
120 views
Acknowledging differentiation of species, in historical times
This is at least partly an historical question, and I am not even remotely a biologist of any sort, so apologies beforehand if it's a little obscure.
I often wonder how many distinctions were made in ...
9
votes
4answers
717 views
What determines a successful protein expression in E. coli?
Some proteins express well in a heterologous host; others- don't. A few requirements are known to determine the protein expression, like a strong promoter (like T7) for transcription and a strong ...
9
votes
1answer
88 views
Why is there an extended delay before G.M. liver cells are attacked by the immune system?
In this BBC article a trial is described where patients with B-Haemophillia are infected with modified Adeno-associated Virus 8 which contained the genes for Factor IX clotting protein. Trials seemed ...
8
votes
3answers
195 views
What kind of event would cause the current Mitochondrial Eve to be replaced by a new one?
Apparently all living humans are matrilineal descendants of a single woman who lived 200.000 years ago. She is called Mitochondrial Eve.
But at the time she lived there was a different matrilineal ...
8
votes
2answers
299 views
How does sodium in one's diet affect blood pressure?
Due to high blood pressure, my doctor has recommended I go on a low-sodium diet. So, that got me wondering what it is about sodium that drives this recommendation?
What does sodium do to a body ...
8
votes
1answer
552 views
Why is GTP gamma S non hydrolyzable?
GTP gamma S is routinely used in studies of G proteins to stably activate the G protein. Comparing the structures of GTP gamma S and GTP, the Sulphur atom replaces the Oxygen attached to the leaving ...
8
votes
1answer
92 views
Why does the gender of the parent species determines the species of a hybrid offspring
I've read a little about hybrid animals, and have been amazed by the fact that the gender of the parent species determine the species of the offspring, in some hybrids.
A male horse and a female ...
8
votes
2answers
264 views
Is it possible to live without health problems sleeping one day and not the other?
Basically, I want to know if it would be humanely possible to sleep one day, skip the next, sleep, skip, sleep, skip, etc, with a 8 hour sleep time.
If you need any extra information, let me know.
8
votes
1answer
184 views
How long does it take for E. coli to shift feedstocks?
With our fermentations we're noticing that it takes an appreciable amount of time for E. coli (K12 variant) to change from being metabolically streamlined on amino acids to being metabolically ...
7
votes
1answer
80 views
obesity risk and single gene polymorphisms
I read a fairly recent meta-analysis of studies into the association between adult obesity and polymorphisms of the FTO gene (Peng et al., 2011). The paper looked at 59 studies and found that "FTO may ...
7
votes
3answers
115 views
Is the appendix a vestigial structure in all vertebrates?
In humans the Appendix is a vestigial organ. Does it serve no apparent purpose in all the vertebrates that have one?
6
votes
1answer
35 views
Is there a normal human melatonin concentration to light level curve?
I'm looking for a graph or a curve that would show the typical concentration of melatonin in blood or saliva for humans over 24 hours. It would be good to know the photoperiod for the same human as ...
6
votes
2answers
82 views
Do omnivore mammals vary food preferences based on dietary needs?
I'm wandering if mammals that can eat many different kinds of food (omnivores) vary their preference for food not only based on the availability, but also based on dietary needs?
I'm looking at this ...
6
votes
1answer
471 views
Why can't humans drink sea water?
Why can't humans drink sea water?
It would seem to be a huge evolutionary advantage for an animal to be able to drink sea water rather than have to rely on fresh water, and it's provably not ...
