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238 votes

Why are so few foods blue?

Short answer Blue color is not only rare in edible organisms - Blue color is rare in both the animal and plant Kingdoms in general. In animals, blue coloring is generated through structural optic ...
AliceD's user avatar
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130 votes

Why are so few foods blue?

Although @AliceD's answer is a great simple demonstration of the rarity of blue in our natural world, there's likely a more nuanced/technical reason. Short answer Blue light was the most available ...
theforestecologist's user avatar
70 votes
Accepted

What is the longest-lasting protein in a human body?

Crystallin proteins are found in the eye lens (where their main job is probably to define the refractive index of the medium); they are commonly considered to be non-regenerated. So, your crystallins ...
Mowgli's user avatar
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51 votes
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Does any molecule other than DNA have a double-helical structure?

A few examples: Starch A polymer of glucose that can form a double helix and functions primarily as energy storage in plants. [image source] f-Actin Filamentous actin forms a helical structure with ...
canadianer's user avatar
  • 17.8k
45 votes

Effects of mRNA vaccines on human body processes

I can address some of the points made in the post. One point about the "artificiality": I think there's one fact that's often overlooked in the discussion of mRNA vaccines. SARS‑CoV‑2, for ...
panda-byte's user avatar
33 votes
Accepted

How did scientists discover HIV?

HIV was identified as an infectious disease through classical epidemiology, and the virus was identified through classical virology. I won't get into the epidemiology, but briefly it went pretty much ...
iayork's user avatar
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28 votes
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Why are sushi proteins called "sushi"? What are the origins of this name?

Because their shape reminded researchers of rolls of Sushi (Ichinose et al, 1990): These repeats were initially called GP-I structures because they were first identified in $\beta_2$-glycoprotein I....
Jack Aidley's user avatar
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24 votes
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Is female the default sex in humans?

Summary: The idea that primary sexual determination defaults to female was proposed several decades ago and is primarily based on the observation that, in the absence of Sry, ovarian development ...
canadianer's user avatar
  • 17.8k
22 votes

What is the longest-lasting protein in a human body?

I like Mowgli's answer, because it is a non-obvious example. However I would also point out that there are many, many protein-based structural components in the body that we know do not regenerate due ...
Meep's user avatar
  • 2,969
21 votes
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Can a human be made with ovum but without sperm?

Nice question! It is actually very difficult to do so because humans, obviously, are far more complex than some animal species which naturally show parthenogenesis. Just to mention, there are female-...
another 'Homo sapien''s user avatar
21 votes
Accepted

What does rescue mean in the context of biological experiments?

"Rescue" in an experimental context means you're capable of undoing some experimental manipulation. It's considered evidence towards identifying a causal mechanism or verifying that your ...
Bryan Krause's user avatar
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20 votes
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Why aren't 'exons' named 'introns'?

The terms intron and exon were coined by Walter Gilbert in a renowned 'News and Views' article, Why Genes in Pieces, published in the journal Nature in 1978. Introns are the intragenic regions and ...
user338907's user avatar
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20 votes
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Is NMDA produced in the body?

(my comment reiterating the answer seemed useful, so I've reproduced it here) There are "NMDA receptors" in our body. There is not NMDA naturally in our body*. "NMDA receptor" is just a name people ...
Bryan Krause's user avatar
  • 46.1k
19 votes
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How hard it is to determine a 3d structure of a protein?

Experimental protein structure determination is hard: the most common method is X-ray crystallography, which can be done in a few months if you are lucky and can take years if you're not. The problem ...
Nicolai's user avatar
  • 4,391
18 votes
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What stops messenger RNA from binding to itself?

It does fold on to itself. There are secondary structures in RNA and some of these secondary structures also have regulatory functions (for example, riboswitches). Some of these structures can also ...
WYSIWYG's user avatar
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18 votes
Accepted

How do ion channels transport only specific ions?

I am restricting the answer to only $Na^+$ and $K^+$ channels, assuming similar mechanism for other channels. In these 2 channels, such high level of specificity is achieved because of two main ...
another 'Homo sapien''s user avatar
18 votes
Accepted

How do geneticists determine if a gene mutation is pathogenic?

The presence of a single variant relative to reference in a single patient is usually not considered adequate evidence to say that the variant causes a patient phenotype. It might be considered an ...
Maximilian Press's user avatar
17 votes

Does any molecule other than DNA have a double-helical structure?

Yes, double-stranded RNA as found in some viruses.
Remi.b's user avatar
  • 68.2k
17 votes

Human Evolution Chromosome 2: Fusion or Break?

The way you answer these sorts of questions is by looking at other, further relatives because that gives you more hints about what the "ancestral" trait is. Since other apes (gorillas, ...
Bryan Krause's user avatar
  • 46.1k
14 votes
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Why should phospholipid non-polar tails be "protected" in the membrane bilayer?

What should be the correct reason for bilayer arrangement? I'll answer your second question first, but there is an almost identical question on this site already: Why do cells have a bilayer? There ...
James's user avatar
  • 11.3k
14 votes

Why do 60S & 40S ribosomal subunits make an 80S ribosome (not 100S)?

When a complex mixture of particles undergoes ultracentrifugation, they separate based on their shape and mass due to the force applied by the centrifuge and the counteracting frictional force of the ...
canadianer's user avatar
  • 17.8k
14 votes

How hard it is to determine a 3d structure of a protein?

I'll address NMR for structure determination. It is the less common method, only ~10% of protein structures are determined this way, though it has e.g. advantages for nucleic acids and more than a ...
Mad Scientist's user avatar
14 votes
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Do proteins generally contain phosphorus and sulfur?

Of the 22 known proteinogenic amino acids, all contain hydrogen, carbon, nitrogen and oxygen. Some (methionine and cysteine) contain sulfur while one (selenocysteine) contains selenium. None contain ...
canadianer's user avatar
  • 17.8k
13 votes
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Crick’s Central Dogma — Counter Cases

Crick’s Central Dogma was actually: The Central Dogma This states that once ‘information’ has passed into protein it cannot get out again. In more detail, the transfer of information from nucleic ...
David's user avatar
  • 26.2k
13 votes

How are DNA virus cladograms actually calculated in practice? Is the procedure different for RNA viruses? Are these processes somewhat subjective?

How are DNA virus cladograms actually calculated in practice? A cladogram, or phylogenetic tree1, is constructed by comparing similarities and differences between organisms, and placing those within ...
Darlingtonia's user avatar
  • 2,659
12 votes

Why do 60S & 40S ribosomal subunits make an 80S ribosome (not 100S)?

The other two answers give nice detail, so I want to give a bit more mathematical answer here. First, the S you are talking about is Svedberg units (of sedimentation coefficient, named after Swedish ...
another 'Homo sapien''s user avatar
12 votes
Accepted

What is the role of glucose in plasmid isolation?

This is a common misconception: in fact, in the alkaline lysis method for plasmid isolation, the glucose does not act as an osmotic stabiliser. Glucose is present in the resuspension buffer at 50 mM. ...
Alan Boyd's user avatar
  • 22.8k

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