1
vote
2answers
210 views

Do any cells change in size or mass as mammals grow?

That is to say, are there cells that, between infancy and adulthood, get larger? Or is all growth done entirely via cell division? I'm wondering if it is safe to assume that the approximate number ...
3
votes
1answer
379 views

Do adipose cells divide in adults?

I have a dim recollection of having heard that when humans gain weight, adipose cells just get larger, rather than dividing. True?
1
vote
1answer
61 views

In a human, what non-germline cells have the highest/lowest mass?

I'm just curious which cells are largest/smallest in the human body other than sperm/ova.
2
votes
1answer
126 views

Histone marks mechanism

I am slightly confused about the mechanisms that makes histone modifications associate with gene expression. That is, H3K36me3 is believed to be present in actively transcribed genes, H3K27me3 in ...
3
votes
3answers
698 views

What makes urine smell acrid?

Occasionally, after someone's been, there is an awful acrid smell lying about long after them. What causes this? The food that they've eaten? Urea less dilute due to dehydration? If it helps I've ...
2
votes
1answer
111 views

Where does an organism store reserves of amino acids?

Where does an organism store reserves of the amino acids it needs to build various proteins it needs -- in the liver ? in the blood ? in every cell ? Thanks
6
votes
1answer
6k views

Will a bone marrow transplant change one's blood type?

Will a bone marrow transplant change one's blood type? Or is the donor blood type matched with the person before transplant?
5
votes
2answers
165 views

How to get smallest subtree containing a set of nodes from BioPhylo?

I'm testing out various phylogenetic libraries in Python. I want to read in a Newick tree, then, given a list of taxa, generate the smallest tree that contains them all. This task is quite simple and ...
6
votes
1answer
79 views

What are the biological mechanisms behind the increase in cancer risk and alcohol consumption?

Alcohol consumption is known to be a risk factor for developing cancer. Compared to obvious causes like tobacco where one is exposed to known carcinogens, I don't see an obvious mechanism by which ...
0
votes
2answers
331 views

Why do living organisms replicate itself or procreate

Why do living organisms spontaneously replicate itself or "procreate" (my understanding is that it does). From a uni-cellular and micro-organism point of view. Is there some sort of stimulant in the ...
4
votes
4answers
973 views

Multiple sequence alignment - how to align everything to 1 gene sequence?

I'm having trouble aligning 3 sequences together - the total gene (~2500bp) and the forward and reverse sequences that are ~1000bp in length. Now I'm using Clustal X2, but the problem is that the ...
4
votes
2answers
626 views

Why is Botulinum toxin the most potent poison known?

Botulinum toxin (trade name Botox) inhibits acetylcholine release in neurons and causes botulism, an acute paralytic disease which leads to nerve degeneration and takes a long time to recover. I've ...
1
vote
1answer
86 views

Interpreting SNP-in-gene associations from GWAS studies

For most SNPs identified in GWAS studies, is the underlying assumption that if it is indeed associated with a phenotype (and lets assume its associated because it affects protein function), that you ...
3
votes
1answer
66 views

Nucleotide frequencies in Kimura's two-parameter model

Here's an excerpt about Kimura's two-parameter model from Felsenstein's Inferring Phylogenies: "The model is symmetrical, and one can immediately see that, after enough time has elapsed, it ...
2
votes
3answers
471 views

Is there such thing as “half-life” of dopamine?

If a dopamine is released at T=0 and binds to receptor D2, what determines the time when the concentration of this neurotransmitter bound to the receptor reaches half of the original concentration? In ...
3
votes
0answers
237 views

Why does vision go blurry after microscope use, and how to prevent it? [closed]

After using a binocular microscope recently for about 20 minutes, my vision went blurry and for an hour or so it was much harder to read small text. This occurs to a (far) lesser extent whenever I use ...
7
votes
2answers
76 views

What is the benefit of near-emptying the bloodstream in the mammalian kidney?

In the normal function of the kidney, the bloodstream is near emptied of fluids as it moves through the glomerulus, in which glomerular filtrate is formed. As it proceeds through the Nephron, a ...
2
votes
1answer
92 views

Have there been any experiments that duplicate chromosome copies from 23*2 to 23*3 or 23*4?

Deinococcus radiodurans is an amazing bacterium with a fantastic survival rate. It can survive to high doses of radiation, in a complete vacuum and in hydrochloric acid. How does this bacterium ...
2
votes
1answer
71 views

Are genes associated with obesity selected for?

I've read that there are several SNPs associated with increased risk of clinical or morbid obesity. I was wondering if there is any evidence that these are under positive selection. Would you expect ...
5
votes
3answers
216 views

Is Leptin Stimulated by Insulin Alone?

What is the mechanism of insulin stimulation in the human body? Is leptin release stimulated by circulating insulin directly? Which other factors are involved in the level of insulin release? My goal ...
10
votes
1answer
572 views

Could a fetus properly develop in micro/zero-gravity?

I suppose another way of looking at the question is: how important is gravity for the development of mammal fetuses? And if things would go wrong, what sort of things would they be, and what would be ...
6
votes
1answer
81 views

What mechanisms tell temperate trees when to drop leaves?

I've been looking around and cannot find a definite answer on what it is that tells trees to change their metabolism and drop leaves. I see that such activity is called Deciduous. What interests me ...
6
votes
2answers
108 views

DAM enzyme distances move along the genome

I am fusing a protein with a Dam enzyme (http://en.wikipedia.org/wiki/Dam_(methylase)). The idea is that when the protein binds to the DNA, the Dam enzyme will start methylating nearby GATC sites, ...
5
votes
1answer
973 views

High Glucose vs Low Glucose DMEM for Cell Culture

I've noticed that in mammalian cell culture, there are often two types of DMEM available. High Glucose and Low Glucose. Does it matter which type I use for culturing of cells (e.g. Hela or HEK293)? ...
4
votes
1answer
319 views

Do effects of caffeine on human body change with habitual use?

I've been reading about homeostatic nature of a lot of neurobiological processes - the brain is trying to maintain a balance by desensitizing receptors, re-uptaking and breaking down ...
3
votes
2answers
94 views

Is there a timeline for the frequency of evolution of any species?

Evolution is traditionally spoken of as an inherited change over generations. Does evolution happen one change at a time - or are there multiple changes occurring between two successive generations? ...
11
votes
4answers
27k views

What is the armpit hair for?

Modern human beings, especially women, cut their armpit hair. It seems to me the armpit hair is trivial/useless. Shortly speaking, what is the armpit hair for?
2
votes
1answer
157 views

Are inflammation and anxiety connected?

I've been reading a curious paper about the use of cannabis, and one of the passages piqued my interest: There’s also been a lot of work done on another constituent of marijuana, cannabinoid, ...
2
votes
1answer
136 views

By What Mechanism can Felines Reverse Diabetes?

To my knowledge house cats (and likely other felines) are the only animal able to go into remission after onset of Type 2 diabetes mellitus. I don't have a reference, this has been by peers in my ...
2
votes
1answer
31 views

What range of dose should be used?

This is a dose-response experiment testing a new cancer drug. the darker line represents cancer cells. what range of dose should be used? I think it's 2-4 because this affects cancer cells only. is ...
4
votes
1answer
167 views

Why do we think chronic inflammation can cause cancer?

Why do we think chronic inflammation can cause cancer? I know the pathway is not fully understood, but what makes scientists believe that inflammation causes cancer?
1
vote
1answer
330 views

How can the Ames test detect a human carcinogen?

Using the Ames test, we add a mutagen to auxotrophic salmonella with mutations in the histidine pathway and rat liver extract to simulate metabolism. How would we know if the carcinogen is a human ...
2
votes
1answer
193 views

What are evolutionary implications of contraception and reduced childhood mortality rates worldwide?

I've heard the following idea this morning: Before the introduction of contraception, humans conceived quite a lot of babies (there was little to do to avoid that), but the population was kept in ...
2
votes
0answers
103 views

Has anyone ever sucessfully translated xRNA or yRNA?

I've recently been researching the subject of size-expanded nucleobases in alternative genetic sets. Many papers describe the, at least, partial success in replicating xDNA and yDNA, as well as ...
6
votes
1answer
7k views

Do crocodiles age?

I was watching a talk by Michio Kaku and he mentioned that crocodiles (or possibly alligators, I forget offhand) don't actually age -- they can die, but they essentially go through no aging process ...
7
votes
1answer
207 views

Recombinant protein fraction in E. coli

If a protein is heterologously expressed in E. coli under the T7 promoter, what fraction of the total protein concentration in the cell is the heterologously expressed protein? What could be its ...
4
votes
2answers
569 views

Does the brain and the body use the same energy source (glucose/ATP)?

I've heard that the brain consumes quite a lot of oxygen and energy, compared to the rest of the body. What I'm interested in is if this is the kind of energy and oxygen that the rest of the body ...
3
votes
2answers
623 views

Difference between mice and rats

What is the actual biological difference between mice and rats? Are they actually the same thing with two different names depending on appearance (are they all mice for instance and we call the larger ...
6
votes
1answer
144 views

What is the difference between xDNA and yDNA?

Wikipedia states that: xDNA contains expanded bases, in which a benzene ring has been added, which may pair with canon bases, resulting in four possible base-pairs (8 bases:xA-T,xT-A,xC-G,xG-C, 16 ...
7
votes
1answer
60 views

Is there such thing as “meters per calorie” for living organisms?

I'm interested in learning if there's some way of quantifying the organism's metabolic efficiency associated with movement. It seems to me that some organisms would be more efficient than others at ...
2
votes
0answers
157 views

Virucides - Herbal and otherwise, for HHV6 type virus or any inner-cell virus

Does anyone know where I can find a reliable list of virucides (not anti-virus) that can be used by humans? This virucide must be able to affect viruses that are already inside the cells. St John's ...
3
votes
1answer
1k views

Is “tonic activity” common for neurons firing in the brain?

I've been reading about Dorsal Raphe Nucleus, a serotonin- rich part of the brain. I noticed mentioning of "tonic activity" - regular pulsing that releases neurotransmitters. On top of this "tone" the ...
6
votes
1answer
275 views

Determining if a specific proline is cis or trans in the protein?

While peptide bonds usually adopt the trans conformation, peptide bonds to proline can exist in either cis or trans conformation. The isomerization between cis and trans is slow, and has been shown to ...
5
votes
2answers
124 views

Is there any biological reason for humans to rest after x days of work?

A lot of people live in a 7 day cycle, where 5 days of work are followed by 2 days of "rest". Vacations and holidays can increase the time available for resting. Is there any biological reason for ...
5
votes
2answers
540 views

The probability of indirect human fertilization?

What is the probability of conception in situations when sperm isn't directly ejaculated into the woman's vagina, like: The man's or the woman's hands come into contact with sperm, for example when ...
4
votes
1answer
212 views

what are the mechanics of sweating?

The causes of sweating aside, i.e. I'm not interested in which and how nerve signals are transmitted to sweat glands. But I would like to read a detailed account on what a sweat gland consists of, ...
8
votes
3answers
2k views

Why is Galapagos island so special?

I am not a biologist so the question may be very stupid. I have no idea. Why did Darwin formulate his theory of evolution just after his visit to the Galapagos island? Why is it so special from the ...
7
votes
1answer
214 views

What preceded ATP synthase?

ATP Synthase is ubiquitous throughout life on earth and so most probably evolved within the last universal common ancestor (LUCA) before that lineage diversified into the various kingdoms of life. ...
1
vote
0answers
28 views

How could a pure culture be represented by more than one ssu rRNA sequence?

Your lab works on an organism isolated from radioactive waste. However, you show that 3 very similar, but not quite identical, ssu-rRNA sequences can be amplified from the culture even though it is ...
-5
votes
1answer
165 views

I believe in variation of a species but not in evolution [closed]

I can see that variation within species exists, for example birds with various size beaks adapted for specific food-gathering purposes, one may have a larger beak vs. smaller beak, OK that works for ...

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