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  #1601  
Old 07-18-2018, 07:11 AM
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Default Re: A Question For The Lone Ranger

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(Generally, a salt in which sodium is the electron donor looks, behaves, and even tastes very similar to a salt with the same electron receiver but potassium as the electron donor.)
I haven't looked close enough to say it's a 1:1 ratio, but a lot of the "low sodium" products use potassium as the replacement for that salty flavor.
Truth, and I use potassium salt in the house. People have noticed the difference.
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  #1602  
Old 09-25-2018, 09:24 AM
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Default Re: A Question For The Lone Ranger

Genetic macular degeneration. I hope I make sense, I'm a wee tired and trying to get this out while I'm thinking of it.

Old man I know, his mother had macular degeneration, and it turns out he picked up the gene too. According to him it's only passed down through women. Now how I understand genes handed down is:

If recessive disorder, woman would need two mutated X chromosomes, and thus 100% chance of passing on an affected chromosome to male or female offspring, and males would have the disorder (In most cases.) Females might pick up the disorder only if father has an affected X chromosome. Otherwise she would be carrying the gene.

If dominant disorder, woman would only need to have one affected X chromosome, could possibly have two but not necessary, and so 50-50 chance of any offspring picking up the gene.

In either case, a son who picks up the gene would not transfer it to his son, as he donates the Y chromosome, but would transfer 100% of the time the affected gene to a daughter.

So:
-Am I recalling high school biology correctly?
-Are there some edge cases out there where such a disorder would not transfer, ever, through the male?
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  #1603  
Old 09-26-2018, 06:38 AM
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Default Re: A Question For The Lone Ranger

There are actually quite a few mutations that can lead to macular degeneration, so it can be an autosomal disorder (in which case, it's inherited the same in males and females) or a sex-linked disorder.

The genetics of such things are a bit more complex than we're generally taught in school, because there are multiple forms of dominance, and it's not always true that a "dominant" allele completely masks the effects of a "recessive" allele. Still, for simplicity's sake, let's assume that this is indeed the case.


So yes, if the trait in question is sex-linked, that means the gene in question is located on the "X" chromosome but not the "Y" chromosome. Since a woman has 2 "X" chromosomes and a man has only 1, such traits will be inherited differently in males and females.


[The distinction between "genes" and "alleles" is sometimes a bit confusing. The gene for a trait corresponds to the region of a particular chromosome that codes for that trait. For example, we might talk about a gene for eye color. Alleles are variants of a gene -- so we might talk about an allele for blue eyes vs. an allele for brown eyes; those would be allelic variants of the eye color gene.]



Anyway, if the trait in question is sex-linked and caused by a recessive allele, the only way a woman could have the condition is if she inherited a recessive allele from each of her parents. (This would mean that her father definitely had the condition, and her mother was at least a carrier.)



If a woman has the condition, then each of her sons is essentially guaranteed to inherit an allele for that trait from her, since each of them inherits his single "X" chromosome from her. And since a son doesn't have a second "X" chromosome that might carry a dominant allele, he will have the condition.

Similarly, each of that woman's daughters will inherit a single recessive allele from their mother, and so will be a carrier at the very least. Whether or not a daughter has the condition depends upon what she inherits from her father. If the father doesn't have the condition, then each of his daughters will receive a dominant, normal allele from him, and so will be a carrier, but won't have the condition. If the father does have the condition, then each of his daughters will receive a second recessive allele from him, and so will have the condition.


So in other words, if the condition is the result of a sex-linked recessive allele, then a woman can only have the condition if she inherits the defective allele from both parents. If she inherits the defective allele from one parent but a functional allele from the other, she will be a carrier but won't have the condition.

If a woman is a carrier and her husband does not have the condition, there's a 50% chance each of their sons will inherit their mother's defective allele and so have the condition. There's no way (barring mutation) a daughter of this couple could have the condition (because each daughter will inherit a dominant allele from her father), but there's a 50% chance that each daughter will inherit a recessive allele from her mother and so be a carrier.

Thus, sex-linked recessive conditions are much more common in males. Given that a male inherits his single "X" chromosome from his mother, if that chromosome happens to carry a recessive allele, there's no way that the man's father could contribute a dominant allele for that trait that would mask the recessive allele's effects.




If a trait is caused by a sex-linked dominant allele, then the situation is basically reversed. In this case, a female has two opportunities to inherit the allele in question, whereas a male has only one.

A man who carries a dominant sex-linked allele will give it to each of his daughters -- and to none of his sons. A woman who carries one copy of the dominant allele has a 50% chance to give it to each of her children -- whether they're male or female.

So yes, sex-linked dominant conditions are more common in females than in males. (Deleterious conditions caused by dominant alleles are rare, however. This is because natural selection can easily weed dominant alleles out of a population, if they have harmful effects. It's much harder to rid a population of harmful alleles if those alleles are recessive.)



Under normal circumstance, since a father does not give his son an "X" chromosome, there is no way that a son can inherit a sex-linked trait from his father. Normally. It is rare, but a translocational mutation can transfer a gene from the "Y" chromosome to the "X", or vice versa. So it is possible (though extremely rare) that a father could pass an allele that is normally sex-linked to his son.
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  #1604  
Old 09-26-2018, 08:25 AM
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Default Re: A Question For The Lone Ranger

I get from that that in a purely binary system I had the basic idea down.

I had to squint and reread a few times though and that just tells me if I presented the old man with that post his head would unscrew and fall off. :) Otherwise what they're all doing is probably the right thing. Communicating with their doctors.

+1 :thanks:
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  #1605  
Old 09-26-2018, 09:23 AM
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Default Re: A Question For The Lone Ranger

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and that just tells me if I presented the old man with that post his head would unscrew and fall off. :)
If this old man has the genes for a head that can unscrew and be removed, I would have thought that would be a much more interest topic of discussion ...
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  #1606  
Old 09-26-2018, 09:32 AM
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Default Re: A Question For The Lone Ranger

Now, a related question for TLR: what actually is a gene?

I'm aware of there being 4 bases C, A, T, G in DNA, and that they pair up. I'm aware (and I think this is universal?) that 3 bases code an amino acid, and that although 3 bases with 4 possibilities for each gives 43=64 possible sequences, we (life on Earth) only have 20 or so amino acids (what happens with other sequences?). And then I think that sequences of amino acids code proteins.

Then what? Are genes these DNA codes for proteins? How does the cellular machinery know where a gene starts and stops? How do we? And least important of all, who comes up with the names for genes, like hox, engrailed (don't know where I remember that from)?
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  #1607  
Old 09-26-2018, 03:22 PM
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Default Re: A Question For The Lone Ranger

Hoo boy, that's something that'll take a bit of time ... after all, "What are genes and how do they work?" is a question to which entire textbooks are devoted -- big, thick, densely-written texts that weigh more than a small child.

I'll try to knock together a decent outline, but it may be a couple of days before I can get to it.
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  #1608  
Old 09-26-2018, 03:52 PM
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Default Re: A Question For The Lone Ranger

Huh? Aren't they just denim and shrink up in the dryer so sometimes it's like trying to put on Spandex. Those genes?

Or, more like Gene Kelly?
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  #1609  
Old 09-26-2018, 04:07 PM
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Default Re: A Question For The Lone Ranger

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Hoo boy, that's something that'll take a bit of time ... after all, "What are genes and how do they work?" is a question to which entire textbooks are devoted --
I started reading the Wikipedia article and :headasplode: I'm glad it's not just me!
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  #1610  
Old 09-26-2018, 05:44 PM
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Default Re: A Question For The Lone Ranger

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I'm aware of there being 4 bases C, A, T, G in DNA, and that they pair up. I'm aware (and I think this is universal?) that 3 bases code an amino acid, and that although 3 bases with 4 possibilities for each gives 43=64 possible sequences, we (life on Earth) only have 20 or so amino acids (what happens with other sequences?).

At least that one's simple. There is usually more than one sequence, up to six, that code for a certain amino acid.
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  #1611  
Old 09-28-2018, 06:04 AM
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Default Re: A Question For The Lone Ranger

Heard on NPR a discussion about DNA searches. One thing particularly caught my attention. The subject of being related to people of historical interest came up. The guest said that after a few generations, you "no longer share DNA with that ancestor". I had no idea.
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Old 09-28-2018, 06:45 AM
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Default Re: A Question For The Lone Ranger

Well, you have to share DNA with your ancestors. The DNA came from somewhere.

It's just that when you go back far enough, you're not guaranteed to share it with any particular ancestor, and even if you do, it might not be very much.

So if you go back 8 generations, you have 256 ancestors (absent inbreeding). Well, on average you'd have 1/256 of your DNA be from each one.

But that's on average. It will vary from that, in a few ways:

1. Mutations can obviously cause things not to match the ancestor's DNA
2. If you're a male, the Y-chromosome would be mostly from the patrilineal ancestor
3. Your mitochondrial DNA comes from your matrilineal ancestor, although it's not a very large amount of DNA comparitively
4. DNA is mostly inherited as whole chromosomes, and there are 46 of those.
5. Crossover (which can also happen to a small portion of the Y-chromosome) will recombine some of those chromosomes, so you can have a chromosome which contains portions from more than one of those 128 ancestors

But still, there are 256 ancestors but only 46 chromosomes... And even accounting for crossover, you likely have some ancestors that you have little or even no DNA from, and some that you have significantly more than 1/256th from. At some point (I don't know when) if you go back far enough you probably don't share any DNA with that person (with exceptions for direct patrilineal* and matrilineal ancestors).

*Probably only if you are yourself a male
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  #1613  
Old 09-28-2018, 03:31 PM
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Default Re: A Question For The Lone Ranger

I wonder how independent those 256 ancestors really are though. Is 8 generations still few enough to neglect 'inbreeding'? (Hardly seems the right word to use, given all breeding would be inbreeding by this definition!)
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  #1614  
Old 09-28-2018, 05:25 PM
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Default Re: A Question For The Lone Ranger

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Heard on NPR a discussion about DNA searches. One thing particularly caught my attention. The subject of being related to people of historical interest came up. The guest said that after a few generations, you "no longer share DNA with that ancestor". I had no idea.

Hairsplitting is necessary here, for one thing we share more than 99% of our DNA to begin with. What the guest meant would have to be qualified as sharing "at least one large, mostly unchanged chunk on the order of a chromosome's worth of DNA".
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  #1615  
Old 09-28-2018, 08:52 PM
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Default Re: A Question For The Lone Ranger

Yes, But made my point but with actual facts about shared DNA, not speculation!
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  #1616  
Old 09-29-2018, 02:09 AM
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Default Re: A Question For The Lone Ranger

There's endless opportunity for speculation here. Let's say most people spend all their lives in a village or the next, how likely is it that one of your ancestors lost a chromosome but then picks it up again from someone else? There are interesting combinatorial problems lurking there that one could put on a math exam.
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  #1617  
Old 09-30-2018, 02:06 AM
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Default Re: A Question For The Lone Ranger

LTR, I believe that some mushrooms are brightly colored so that you know they are toxic, but what about animals that are 'color blind', are there other clues that would tell them to not eat certain mushrooms? or do they just not eat mushrooms at all? I understand that most birds do not have a sense of smell and that some animals are 'color blind'.
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Old 06-12-2019, 09:50 PM
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Default Re: A Question For The Lone Ranger

This recent APOD picture is just delicious to look at.



But here's the question for TLR.

We're always told that Jupiter is a gas giant and all the colourful stuff we see is clouds.

But looking at the above I see fluffy white bits that look like Earth clouds (specifically, cumulus clouds) do in satellite photos, like this bit and this bit .
They have shadows. And they occur over that colour "ground". So it seems to me that they are formed by clear air moving relatively fast across the "ground" until it hits that presumably warmer region and is forced upwards forming these condensation clouds.

Whereas the great majority of the picture, and Jupiter in general until I saw the above fluffy white clouds, looks like this area: - turbulent for sure, but a slower movement of fluids, like algal blooms in lakes or maybe smoke in still air.

So my my theory is that Jupiter might be gassy but the most of the surface is pretty dense and fluid-like, and on top of that it has actual ephemeral clouds like on Earth.

Is my exometeorology, my planetary fluid dynamics along the right lines?
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  #1619  
Old 06-13-2019, 12:07 AM
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Default Re: A Question For The Lone Ranger

Well, as you go deeper into the atmosphere of Jupiter (or any of the gas giant planets), the pressure increases. Eventually, the pressure is such that the gases essentially become liquids.

So yes, Jupiter essentially has a more or less liquid "surface" with layers of less-dense, less-compressed gases floating above, forming the various layers of clouds.

(Some of the clouds are primarily water vapor, some are primarily methane, etc. That's partly why there are so many different layers, and why they're different colors.)


It's speculated (though by no means universally accepted) that Jupiter does have a solid core under all that compressed gas. The core, if it exists, is thought to consist of a mixture of various heavy elements. Surrounding the core is a layer of super-compressed, liquified hydrogen and helium; surrounding that, of course, are layers of gases -- mostly hydrogen, with some helium and much smaller amounts of ammonia, methane, water vapor, and other trace gases.
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  #1620  
Old 06-13-2019, 04:41 PM
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Default Re: A Question For The Lone Ranger

One of the fun things about fluid dynamics is many effects are caused by dimensionless values and so scale exceptionally well.

The Reynolds number of a fluid is one of them and models the transition between laminar and chaotic flow with certain novel behaviors happening along the way, and is just a ratio between density, velocity, and viscosity. Gasses are as much a fluid as liquids and if the flows share the right ratio of reynolds numbers they will interact in a similar way. As these characteristics are easily to describe with only a few numbers there are many combinations of variables that create the same effect. So what you are seeing is indeed a gas ‘cloud’ that is tiny droplets of condensed liquid in a gas atmosphere but is behaving in a manner closer to how a liquid would on earth because the ratios of flows are similar to the ratios we see in liquids on earth.

The dense clouds suggests the atmosphere is saturated so standing in it would probably feel like some ungodly maelstrom of a storm but still a windy storm and not a liquid ocean. As it’s a balancing act of variables scientists have managed to reproduce flow behavior normally seen in liquids or air but instead in sand, as well as laminar sheer effects commonly seen in sand but in a liquid, etc.

At this point I don’t know enough about Jupiter’s atmosphere to go much further, except that as TLR has said there’s probably an ocean down there somewhere but with the crazy pressure increase matter can start acting in unexpected ways so I couldn’t say if there’s a delineation between the atmosphere and ‘sea’ of if it just gets foggier and foggier like an ever thickening mist.

Which doesn’t quite get to the question and also you’re right those are condensation clouds of ammonia and part of a separate layer of the atmosphere.
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  #1621  
Old 06-14-2019, 07:15 PM
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Default Re: A Question For The Lone Ranger

What's the difference between van der Waals force and a hydrogen bond?

I was reading about van der Waals forces and I thought "that sounds an awful lot like a hydrogen bond" so I looked up hydrogen bond and it say: "There is general agreement that there is actually a minor covalent component to hydrogen bonding, especially for moderate to strong hydrogen bonds (> 5 kcal/mol), although the importance of covalency in hydrogen bonding is debated. At the opposite end of the scale, there is no clear boundary between a weak hydrogen bond and a van der Waals (e.g., dipole-dipole) interaction."

So yeah, they're close but not exactly the same?

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Old 06-18-2019, 01:29 AM
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Default Re: A Question For The Lone Ranger

As I understand it, there are several different definitions used for "van der Waals" forces. Some define van der Waals forces as "all intermolecular forces except Hydrogen Bonds," while I've seen other sources define van der Waals forces as "any intermolecular force, including Hydrogen Bonds."

So, I guess it depends partly on who's defining the term. Regardless, there's no clear and hard boundary between hydrogen bonds and [other] van der Waals forces. Whether they're considered separate things or whether a hydrogen bond is just another of the van der Waals forces seems to depend entirely on who's defining the term.
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  #1623  
Old 06-29-2019, 12:58 AM
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Default Re: A Question For The Lone Ranger

Why do prion diseases seem to only affect the brain?

I'm aware that they can accumulate in other tissue, but it seems that prion diseases are really only a problem if they get in the brain.
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  #1624  
Old 06-29-2019, 08:08 PM
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Default Re: A Question For The Lone Ranger

Prion diseases can occur in tissues other than nervous tissues, as you've noted. Nonetheless, they're most common in the Central Nervous System -- why is that?

Let's talk about proteins first. Every protein starts out as a chain of amino acids; these amino acids ultimately "fold" into a 3-dimensional, functional protein. Prions are proteins that mis-fold and are non-functional. Worse, a prion can cause normal forms of the same protein to mis-fold as well -- which is why it's infective.

Masses of mis-folded proteins form "plaques" called amyloids, which damage and ultimately kill cells. Creutzfeldt-Jakob disease is a relatively well-known disease caused by prion infection, as is kuru (which is most easily transmitted when someone eats infected nervous tissues) -- both cause deterioration of the Central Nervous System and ultimately, death.


A common protein found in the membranes of cells throughout the body is known as PrPC. While its exact function isn't clear, it appears to be associated with cellular communication -- that is, it allows cells to communicate with each other and coordinate their activities.

A healthy person produces various proteases, which digest and destroy proteins that are present in excess amounts, or that have become damaged somehow. PrPC is readily digested by a particular proteinase, Proteinase K, and so does not accumulate abnormally in tissues.

If PrPC mis-folds, it can form PrPSc, a prion. PrPSc converts nearby PrPC proteins to PrPSc, and so these amyloid plaques accumulate in cellular membranes. Unfortunately, PrPSc is very resistant to proteases, and so it's difficult for the body to get rid of the prion, once it arises.


But why is this such a problem in the Central Nervous System? Well, PrPC proteins are especially common in the cells of the CNS. If, as appears to be the case, PrPC proteins help cells communicate more efficiently, it makes sense that they're especially common in cells of the CNS.

Anyway, that appears to be the reason why prion diseases are so commonly associated with the brain and spinal cord -- that's where PrPC proteins are most concentrated, and so those tissues are the most vulnerable to prions.
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  #1625  
Old 06-30-2019, 10:25 AM
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Default Re: A Question For The Lone Ranger

Part ii. (:infinity: marks)

Are prions alive?
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