Recent comments in /f/askscience

Alfred_The_Sartan t1_jck6b4a wrote

Reply to comment by Gedankensortieren in What makes one greenhouse gas stronger at trapping heat than another? by sand_eater

Does size of a molecule play into how high in the atmosphere it can get? Like is it that the bigger ones get warmer and therefore rise like a box of legos or does the mass keep them generally lower due to gravity? I feel like I’m overthinking this and that the effects of molecular size to dispersion are negligible

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supapoopascoopa t1_jcjvu3o wrote

Reply to Are there any known endogenous retroviruses that can cause active infections, and is this possible in principle? by amlyo

Endogenous retroviruses are defective, only vertically transmitted like other genes, and none yet found are competent to produce virions. But they are all in some sense heritable infections and also “infect” new cells every time a cell divides.

Some can produce proteins and even entire viral like particles using host machinery. These proteins are associated with autoimmune diseases and certain cancers. One could argue these are “active” infections in terms of causing symptoms.

The takehome message as usual is that nature in general and viruses in particular don’t give a hoot about arbitrary definitions.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1187282

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ScienceIsSexy420 t1_jcjpya6 wrote

Reply to If you isolated a gene from an animal that produces an enzyme how do you isolate and synthesize the enzyme it produces? by 2handsandfeet

In terms of pharmaceuticals, this is usually done by inserting the gene of interest into a vector, or a piece of DNA used to transform an organism. This vector is then inserted into a bacteria, usually e.coli where the enzyme of interest is produced. Then it is a simple matter of harvesting the enzyme from the bacteria.

When doing this, design of the vector is of utmost importance. The gene of Interest needs to be placed under control of a transcriptionally active promoter, as well as including some sort of selection mechanism. This is usually done with resistance to a certain antibiotic that the culture is grown in the presence of, ensuring other bacteria cannot contaminate the product.

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zumiaq t1_jcjikri wrote

Reply to How would a scientist be able to tell the difference between a blood sample from two totally different animals? by EastClintwood89

One way would be to simply look at the blood underneath a microscope. If you take a smear of the blood and then stain it with various dyes, blood cells would look different between different species.

The differences would be more extreme the less-related the species. For example, the red blood cells of reptiles and birds still have a nucleus and look like oval eyes. Human red cells, on the other hand, are just red circles-- slightly lighter in the middle than the sides.

Amongst mammals the differences might be a bit more subtle. For example, you might look for a specific type of white blood cell called a eosinophil. They aren't common but if you search the slide you'll probably find one eventually. Eosinophils have a lot of large granules in them that look pretty different from animal to animal.

There are, of course, many many other ways to identify the blood. Some are much more precise than this (genotyping being the obvious one.) But a peripheral smear is low-tech, inexpensive, and I think most fun.

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Gedankensortieren t1_jcjhd3p wrote

Reply to What makes one greenhouse gas stronger at trapping heat than another? by sand_eater

In a very simple and handwaving picture: molecules can vibrate and rotate upon absorption of electromagnetic radiation. But these are quantized energy levels. The absorption spectrum, hence the number of possible absorption lines depend on the molecule.

For example O2 has two atoms. They can vibrate against each other resulting in one set of spectral absorption lines.

CO2 has already three Atoms. Hence you get vibrational modes for first C versus the O atom, for second C versus O atom and for C versus C atom. This gives you several sets of spectral absorption lines.

As well you get different numbers of rotational absorption lines depending on the demension of the molecule. Helium is 0D, O2 and CO2 are 1D, H2O is already 2D because the angle between the bonds is not 180 degree. Methan is an example for a 3D molecule. The higher the dimension, the more modes of rotation are possible.

In general more complex molecules have more rotational and vibrational modes hence they absorb a larger number of spectral lines. Hence they absorb more infrared radiation.

For more details and a more physical mathematical description have a look at infrared spectroscopy.

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