All Questions
8
votes
1answer
185 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 ...
8
votes
2answers
1k views
How is eye color in humans inherited?
In high school we studied the inheritance of eye color, as it was explained to us in the most simple way: blue eye color is a recessive, monogenic, autosomal trait. Now I know that it is a bit more ...
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
117 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
54 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
91 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
621 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 ...
6
votes
2answers
194 views
Is there such thing as a generic “metabolic type”?
A while ago I picked up a book called "Eat right for your metabolic type". The book discussed the effects of the endocrine system on the overall shape and the speed of metabolism.
The book outlined ...
6
votes
1answer
213 views
X chromosome “weight”?
According to Wikipedia, the X chromosome has approximately 153 million base pairs, while the Y chromosome has only 60 million base pairs. Thus, the difference is roughly 93 million base pairs.
My ...
6
votes
2answers
115 views
What is the eye muscle status when you stare at distant view through a glass wall?
The book said when you look at object close to you, the eye muscles contract and vice versa. I wonder what will be the status of the eye muscles when I stare at distance view (such as a mountain) ...
6
votes
2answers
421 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 ...
6
votes
3answers
159 views
Where can I find the common names for the zoology taxonomy?
Forgive me if my question does not belong here or if I'm using incorrect terms, but I'm not educated in biology at all. I'm investigating the workings of the biological classification system.
I was ...
5
votes
2answers
77 views
How does a pinched nerve cause pain (at the molecular level)?
Is this due to pressure differentials in the surrounding tissue? (Is it possible to have a pinched nerve without compression of the surrounding tissues, and does this cause pain?)
What are the ...
5
votes
1answer
75 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 ...
5
votes
1answer
76 views
Number of spindle fibres during Metaphase?
During metaphase, the chromosomes are arranged on the equatorial plate and are attached to spindle fibres. After S phase, can the cell be said to attain the configuration of 4n?
Also, during ...
5
votes
2answers
174 views
Survival of E. coli on agar plate at -20 degree C without glycerol stock
If I kept E. coli transformed with plasmid at -20˚C without making glycerol stock, will it survive? Actually I have kept it this way for 18 hours. What will happen with it? Will it grow in fresh ...
5
votes
3answers
500 views
How did butterflies evolve to have eyes on their wings?
Some butterflies, such as the UK native Peacock butterfly (Google Image Search) have markings on their wings that look just like eyes, complete with a white fleck to imitate a convex, transparency ...
5
votes
1answer
132 views
Is ovum + ovum fertilization possible for human?
In humans is it possible to fertilize a ovum with another ovum from the same female subject?
I already found some works in which the ovum is fertilized by a somatic cell (see e.g. this ), but I am ...
5
votes
1answer
139 views
What is an simple way to burn glucose for visible effect?
I want to make a partially working model of the digestive system that could digest complex carbohydrates. My ultimate goal is to be able to cut up some bread, put it into the model, operate it, and ...
5
votes
1answer
318 views
The genetic and physiological origins of laughter?
This Wikipedia article defines laughter in many terms, such as...
"a visual expression of happiness, or an inward feeling of joy"
and
"a part of human behavior regulated by the brain, ...
5
votes
1answer
618 views
How do SDS-PAGE gels differ in a Bis-Tris system vs. a Tris-Glycine system?
Protein migrate differently in Bis-Tris and Tris-Glycine gels. I was curious about the actual reasons why. Do certain gel systems result in a tighter resolution than others?
5
votes
1answer
557 views
What is the distinction between F' plasmid and R plasmid?
Is there a difference between an F' plasmid that has taken up a chromosomal gene that conveys antibiotic resistance, and an R plasmid? Is a bacterium containing an R plasmid and yet lacking an F+ ...
5
votes
3answers
605 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 ...
4
votes
1answer
87 views
Can forensic DNA analysis be used to generate a visual approximation of a suspect?
In light of the current US supreme court case, I'm curious if enough information can be teased out of a DNA sample to get a "reasonable" approximation of the suspect (never mind the legality). I ...
4
votes
1answer
110 views
How does hemoglobin-free blood transport oxygen?
Snails... We have some kind of huge garden snails appearing lately (read since the last 10 years or so). Try as one might, it's impossible to avoid them when driving. These snails do not appear to ...
4
votes
1answer
86 views
What protocol does the nervous system use?
I just read How does an inhibitory synapse communicate to the cell body of a neuron? and found myself asking this question ... hopefully I'm not asking the same thing
Any body possessed of a nervous ...
4
votes
3answers
119 views
Since Darwinian times, has there been any striking/notable effects of evolution on humans?
I understand that evolution is constant process that acts on a population in successive generations. Thus, it is obvious that evolution is happening. However, I'm curious as to the stricking examples ...
4
votes
3answers
762 views
Is the theory of evolution being disproved by bats?
For some species the Darwin's theory evolution makes perfect sense. I can easily imagine how, for example, the giraffe has evolved to its current appearance: the natural selection was favoring ...
4
votes
1answer
125 views
Why would deers keep crossing a river full of crocodiles while some of them have been killed?
I recently watched a clip on Discovery Channel, where I saw deers crossing a river full of crocodiles, ignoring the fact that some of them would have been killed doing so.
What could be an ...
4
votes
1answer
982 views
Do humans have Coelom?
Kimball Biology 5e says
Coelom is the main body cavity of many animals. It is lined with an epithelium derived from mesoderm.
Gilbert Embryonal Biology 9e says
Coelom is the space between ...
4
votes
2answers
5k views
Does Human Female Meiosis II occur after fertilization with sperm?
I am reading the answer and I am getting confused by the sentence:
At the end of meiosis I females have two daughter cells and meiosis II
only occurs if and when fertilization occurs by a sperm ...
4
votes
1answer
313 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 ...
3
votes
2answers
31 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 ...
3
votes
2answers
178 views
What is the function of nodes of Ranvier in axons?
In a neuroscience class I'm taking, it was explained that myelin covers axons in sections, the uncovered sections are called nodes of Ranvier, and signals propagate much faster in the covered ...
3
votes
2answers
55 views
Do dolphins really sleep?
I have always wondered, if dolphins sleep with one eye opened, do they really sleep at all?
According to this article dolphins indeed shut down their brains.
I already googled it. No help from ...
3
votes
2answers
271 views
What is the evolutionary rationale for palm sweating?
Sweaty palms seems to be a reaction to stress, anxiety, etc. For our forest-inhabiting primate ancestors sweaty palms could cause unwanted side-effects such as slipping off tree branches under ...
3
votes
1answer
75 views
How are melatonin levels measured in humans?
I'm wondering how it is possible to measure diurnal variations of melatonin levels in humans. I keep reading that there should be a large difference in amplitude between melatonin levels measured at ...
3
votes
2answers
102 views
Ultrasound during pregnancy
In a hospital I can see a long queue of pregnant women waiting for their turn for ultrasound. Is it safe to go through the ultrasound during pregnancy, especially during last few weeks?
Is ...
3
votes
2answers
150 views
Why is the frog genome so much larger than a fish's?
As we have heard in the summaries of the human ENCODE project, 80 per cent of junk DNA appears to have an essential function. Many fish have a genome with only one tenth the size of a usual vertebrate ...
3
votes
1answer
130 views
Could inhibition of progerin formation slow the rate at which a body ages?
According to wikipedia, progerin is activated in senescent cells. The protein itself is known to be the cause of a rare affliction 'progeria' - a disease marked by accelerated aging of the body. This ...
3
votes
1answer
171 views
Human sleep cycles and dream times, what influences the timing and intensity? Sleep history included
I'm doing sleep and dreams research and have developed an iPhone application to help me track my bedtime, rise time, sleep onset and also mark dreams. The app also monitors overall activity overnight ...
3
votes
1answer
488 views
Is secondary follicle or Graafian follicle arrested in the second metaphase of oogenesis?
My note about which I am not sure:
Secondary oocyte is arrested in the metaphase II monthly after puberty until fertilization with sperm.
The following picture also satisfies my sentence: .
So ...
2
votes
1answer
54 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?
...
2
votes
2answers
112 views
What would it take to recognize a deer by its photo?
I am trying to recognize a deer by its antlers or any other means.
Elaborating:
I was hoping to use their antlers to recognize them but I have heard that most deers shed their antlers every year so ...
2
votes
1answer
72 views
Expanding the SETI initiative to seek intelligent data within DNA sequences?
I've recently read a couple articles dealing with long term data storage, and DNA was suggested as one of the prime candidates for long term storage of digital data additionally, there is this article ...
2
votes
3answers
363 views
Can the third sex be categorized as Male or Female?
Hijra are people who have a penis (not sure if sexually active) but look much like a female (perhaps for some feminine biological property). Wikipedia says they are "physiological males who have ...
2
votes
1answer
82 views
Circulation through the liver in light of drug metabolism
I have a lingering question which stems from an answer that I gave to What hydrolyses aspirin within the digestive tract and blood stream?
When a drug or any other substance is absorbed into the ...
1
vote
1answer
99 views
What is this insect?
These photographs were taken today in Marseille, in the Mediterranean coast of France. My French friends inform me that these beasties are called cousins because they are "cousins" of mosquitoes ...
1
vote
1answer
26 views
What's seen when stress echocardiography shows ischaemia? Can this happen without angina?
What can be seen on the screen when stress echocardiography (a pair of heart ultrasounds before and after exercise) suggests ischaemia? Can this happen without chest pain?
Illustration from ...
1
vote
1answer
32 views
By what mechanism does elevated homocysteine level accelerate thrombin formation?
It has been stated that elevated homocysteine level accelerates thrombin formation. By what mechanism does this happen?
