5
votes
1answer
88 views

What is the total number of rounds of cleavage during mammalian embryonic development?

That for frog is 12, but what about mammalian embryos? I cannot find the exact number anywhere.
6
votes
1answer
4k views

Does consuming sodium benzoate (preservative E211) cause problems during pregnancy?

There seems to be strong evidence to support the claim that sodium benzoate (E211) causes hyperactivity in young children, e.g. Bateman et al. (2004) and McCann et al. (2007). This leads me to ...
7
votes
2answers
312 views

Can a living organism run on electricity?

Each time I'm too lazy too cook I think it'd be cool to be able to just plug myselt into an outlet. Yet I know it is not possible - I need amino acids and a lot of other stuff that electricity can't ...
6
votes
1answer
933 views

What is the average Leg-to-Foot Length/Width Ratio?

I'm making a program that estimates a probable size (widest width and longest length) for a human's foot given the length and width of the leg to which it is attached. However, try as I might, I can't ...
67
votes
2answers
1k views

How many times did life emerge from the ocean?

Evolution is often mistakenly depicted as linear in popular culture. One main feature of this depiction in popular culture, but even in science popularisation, is that some ocean-dwelling animal sheds ...
29
votes
3answers
2k views

Why is polyploidy lethal for some organisms while for others is not?

Polyploidy is the multiplication of number of chromosomal sets from 2n to 3n (triploidy), 4n (tetraploidy) and so on. It is quite common in plants, for example many crops like wheat or Brassica forms. ...
5
votes
3answers
1k views

Why does so much variation exist within species?

My last phrasing of this question did not go down well, so I will try again. The genotype of species is not always the same. If you ask yourself why not all of these possible expressions except one ...
12
votes
1answer
3k views

How does Golgi's neural histological stain work?

What is known about the targets of Golgi staining of neurons? Are larger neurons more likely to be stained? Are specific cell types more susceptible than others? The current wikipedia article says ...
15
votes
2answers
2k views

Harmless virus?

Is it possible for a virus to live symbiotically with its host? Is the human body plagued with viral infections that do negligible harm, or even serve a beneficial role?
12
votes
1answer
4k views

Why does scar tissue change color?

I was wondering why, when you are cold, scar tissue turns bluish or purple while original skin stays the same color. The only thing I can think of, is that maybe scar tissue gets less circulation ...
3
votes
1answer
182 views

How do you see the stage of the second meiotic arrest in oogenesis in the given video?

My old question raised this new question. After reading this page I can say now that metaphase is the stage in which the second meiotic arrest occurs within oogenesis: The oocyte is arrested again ...
7
votes
3answers
2k views

If I put a cup over a spider, and leave it there for a day, will the spider survive?

Will it travel more slowly since it hasn't had food for a day? What if I left the cup there for longer?
7
votes
1answer
196 views

Does cooking ginger reduce its anti-nausea effect?

There seems to be strong evidence to support the hypothesis that eating ginger helps reduce nausea e.g. during pregnancy (e.g. Vutyavanich et al.). It seems that gingerol is the active ingredient in ...
9
votes
1answer
888 views

Why do some plant species have lobed leaves, while similar species in the same habitat don't?

Some plants have lobed leaves, like the English oak (Quercus robur), while other plants growing the same deciduous woodland habitats, and very often growing alongside oaks, such as the European beech ...
6
votes
1answer
167 views

What's a good reference for choosing histological staining chemicals?

It's often difficult to find the appropriate or best stain to use when I want to examine a new type of tissue. I think that's partly because many histological techniques were developed a long time ...
10
votes
2answers
4k views

How do I clean phenol contaminated RNA without losing any of the sample?

I recently extracted RNA from developing plant leaves for the first time, as part of a very long and intensive experiment. The samples were extremely precious because of the amount of effort that went ...
5
votes
1answer
654 views

How does water buffer a sudden drop in temperature?

A property of water is that it is slow to heat and cool. According to my biology book, some energy from an increase in temperature would spent breaking hydrogen bonds, so that temperature does not ...
7
votes
2answers
564 views

What effect does ambient temperature have on the cardiovascular system?

I am sorry if this is not appropriate for this site, but I think it fits so I am asking it here: I went for a run yesterday, and it was about -8 degrees Celsius. I was wearing a couple pairs of ...
16
votes
1answer
911 views

Do insects' muscles become stronger with exercise?

I am curious to know if insect muscles become stronger with exercise, because I have seen many insects get tired out, but I have never seen one get stronger. They always seem to become permanently ...
11
votes
3answers
480 views

Is Behe's experiment (evolving the bacterial flagellum) plausible in the lab?

[Warning: this question is motivated by a prominent proponent of "intelligent design": Prof. Michael Behe. I'm not interested in debating creationism.] According to Wikipedia[1]: In Darwin’s ...
5
votes
1answer
324 views

How do you turn a minimal CIF description into a complete one?

I have a CIF file that I downloaded from the PDB, but if I try to use it in Coot, it complains that it is not a complete CIF definition. This page provides a batch script that I may be able to tease ...
6
votes
1answer
3k views

What cells would have the CD3 marker on them (other than T-cells)

Do you know of any peripheral blood mononuclear cells that would express any amount (beit low or high) of CD3 on their surface (other than T-cells)?
6
votes
2answers
282 views

What is a good Non Fluorescent DNA Dye?

Can anyone suggest a dye which specifically targets DNA, but is not fluorescent? (We plan to mark DNA before observing it with RAMAN-Spectroscopy. Because of the weak Signal even a low emission would ...
12
votes
5answers
316 views

Is it the case that all changes in phenotype during life are not inheritable?

This came up in a talk with a friend. I wanted to clear this doubt. I've read about it before and did again after her remark (my thoughts didn't change: her concept is Lamarck's, not Darwin's), but ...
24
votes
1answer
582 views

How long will a vegetable live for after being harvested?

I understand this might depend on the types of vegetables, but is there an average or studied specifics? Does it die immediately? Is there a way to precisely diagnose death in plants? If so, what are ...
6
votes
1answer
316 views

Why are beta-galactosidase proteins overexpressed in senescent cells?

Wikipedia explains that it's a hypothetical hydrolase enzyme that catalyzes the hydrolysis of β-galactosides into monosaccharides only in senescent cells. I'm just wondering - what causes it to be ...
5
votes
1answer
183 views

Why isn't the p16-INK4a gene involved in apoptosis expressed in heart or liver tissues?

New York Times article explains how killing p16-INK4a positive senescent cells can help keep the surrounding cells vigorous. So here's my question: why is p16-INK4a expressed in most cells other than ...
4
votes
1answer
881 views

How do caspase proteins kill a cell?

Wikipedia just says... The active effector caspases then proteolytically degrade a host of intracellular proteins to carry out the cell death program. Okay, but what parts of the cell do they ...
7
votes
1answer
130 views

How exactly does long-term tension (over months) build up in the ligaments, tendons, muscles?

And is there any basis for believing that massage relieves that tension?
-3
votes
2answers
3k views

At what stage of meiosis does “first meiotic arrest of oogenesis” occur?

An exam question asked what stage of meiosis corresponds with "first meiotic arrest of oogenesis". I can't work out the answer from the wiki page - can anyone explain which step this refers to?
8
votes
1answer
601 views

Why do dendritic cells have CD4/CD8 on their surface?

Why do dendritic cells have CD4 or CD8 antigens on their surface? What is their function without the presence of a T-cell receptor?
4
votes
1answer
117 views

What evidence gives clues to the physiological basis for conversion disorder?

Conversion disorder has a set of DSM diagnosis criteria, which, among other things, includes ruling out all neurological disease. However, as the media has shown us (and one could argue a biased ...
11
votes
2answers
5k views

Does an annealing temp higher than primer's Tm contribute to primer dimer?

I am attempting to reproduce results from a number of journal articles all referring to the same SNP. In doing this I'm using the same primer set outlined in the articles. When I attempted a run the ...
11
votes
2answers
299 views

What are the limitations to current nucleotide sequencing technologies?

Using the Illumina platform, it is cheap and (relatively) easy to sequence huge amounts of DNA or RNA. There are various other platforms out there (Roche/454, SOLiD, PacBio, Ion Torrent) each with ...
7
votes
1answer
65 views

How are whole Haplotypes for Sequencing isolated?

Is it possible to reliably isolate and amplify DNA from individual sperm and/or eggs (from a fish)? I'd imagine that the small amount of DNA would make the PCR a bit wacky. We've considered ...
9
votes
1answer
155 views

Is it correct to regard archeaic humans (i.e.n Neanderthals and Denisovans) as distinct species to Homo sapiens?

There is increasing evidence (e.g. here) that Homo sapiens interbred with contemporary homonins such as Homo neanderthalensis and the "Denisovans". Although these homonins do show differences in their ...
8
votes
1answer
54 views

Downloadable worldwide database of disease statistics?

I am looking for a downloadable database of disease statistics. I have emailed the good folks over at HealthMap, but they haven't gotten back to me yet. As far as I can tell, their data relevant to ...
17
votes
3answers
985 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 ...
11
votes
1answer
126 views

How would one calculate the availability of nucleotides to an enzyme?

How would one calculate the availability of nucleotides to an enzyme like a polymerase ? I imagine an answer in units like nucleotides per second per enzyme, but I'm also imagining an answer that is ...
6
votes
2answers
731 views

How does an inhibitory synapse communicate to the cell body of a neuron?

I picture a neuron as having multiple trees of dendrites attached to the cell body with a single axon leaving the cell body. I believe the cell body near the axon root makes the decision to fire or ...
7
votes
1answer
381 views

How do you knockout an E. coli gene without disrupting the rest of the gene cluster?

I'm familiar with the method to build Keio collection using single-gene deletion with an antibiotic cassette. However, what happens when there are gene clusters or overlapping ORFs and you still only ...
10
votes
1answer
239 views

Does the genetic expression of specific physical traits ever correlate to behaviour?

Over at skeptics, there were a couple questions asked as to the correlation of specific physical traits in relation to personality/behaviour. For instance, the simian line as well as red hair. Now, ...
34
votes
4answers
7k views

How does the brain's energy consumption depend on mental activity?

What is the impact of mental activity on the energy consumption of the human brain? I am most interested in intellectually demanding tasks (e.g., chess matches, solving a puzzle, taking a difficult ...
4
votes
2answers
1k views

Why would taking antibiotics increase stamina and energy?

I often hear that people who are taking antibiotics experience wild fluctuations between feeling full of energy and completely alert but soon after feeling impossibly fatigued and sick. Does this ...
9
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 ...
8
votes
1answer
806 views

Is there a correlation between muscle fibers and body types?

I have been told the number of muscle fibers a particular muscle has varies from person to person. Unfortunately, the person who told me this did not know much more than this. Initial searching on the ...
9
votes
5answers
487 views

What is meant in biology by the term “evolved”?

A student asked me this the other day and I thought that I would ask it again here. If one organism is said to be "more evolved" than another, what exactly does this mean?
4
votes
1answer
134 views

What are the constraints when growing an artificial brain?

Are there any experiments on growing artificial brains from brain tissue? What are the constraints? Will such tissue grown to the mass greater than that of human brain surpass it in intellect or it ...
5
votes
2answers
469 views

How are the gene sequences of individual sperm and egg cells “randomized”?

What I mean by "randomized" is, in the place where an egg cell or sperm cell is made, what is the mechanism by which each one is not made identically? Though I am a layman, I'm pretty sure that if the ...
7
votes
2answers
545 views

Did human hairs actually evolve from scales?

What is the evolution of hairs? Did they evolve from scales?

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