Anyone good at population genetics? - The Horse Forum
Old 11-30-2012, 01:23 PM Thread Starter
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Anyone good at population genetics?

So I'm having a bit of a brain fart on some extra credit work for genetics. I could ask the professor but she's not too nice and I already fought about horse colors with her before and she doesn't like me

It's with population genetics. To sum it up a fictitious herd of horses was abandoned to breed amongst themselves completely isolated. Original herd has one palomino paint stallion, one sorrel stallion, four sorrel mares, one palomino mare, and one sorrel paint mare. The herd has grown to 90 since then.

I'm going to assume "paint" means just tobiano...as that's the only white patterned mentioned anywhere on the paper. *sigh*

Obviously there's ee, CCcr, CC, TO?, and toto in the gene pool.

First question is saying in the modern herd, 11 out 90 horses are cremello. Assuming the herd is in Hardy-Weinberg equilibrium, what are the frequencies of the C and Ccr alleles?

Hardy-Weinberg equation is p^2 x 2pq x q^2

I know how to figure that out but she usually gives us the number of recessive (or in this case the chestnuts). And normally we figure out all three and not just two... Plus she's always given us examples where both homozygous dominant and heterozygous are the same colors and this is not the case with the cream gene.

If I calculated it right so far I have the frequency of cremellos at .34 and but I don't know how to figure out how many palominos and chestnuts are in the remaining 79.

Help?
Bridgertrot is offline

Old 11-30-2012, 02:29 PM
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Math!! *runs away*

I would really love to help, but I lack the general mathematical processing genes most people have.
Poseidon is offline
Old 11-30-2012, 03:01 PM
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Oh lord im having flash backs of college genetics class. I'm with Poseidon run away lol! I want to help you but even though I have a biology degree math is not my strong suit. I'm too scared I'd give you the wrong answer as its been a few years since I've had to look at that equation. Too bad my boyfriend is gone camping with a troup of boy scouts till Sunday he'd be the perfect person to ask that.

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Peppy Barrel Racing is offline
Old 11-30-2012, 11:05 PM
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Originally Posted by Bridgertrot View Post
So I'm having a bit of a brain fart on some extra credit work for genetics. I could ask the professor but she's not too nice and I already fought about horse colors with her before and she doesn't like me

It's with population genetics. To sum it up a fictitious herd of horses was abandoned to breed amongst themselves completely isolated. Original herd has one palomino paint stallion, one sorrel stallion, four sorrel mares, one palomino mare, and one sorrel paint mare. The herd has grown to 90 since then.

I'm going to assume "paint" means just tobiano...as that's the only white patterned mentioned anywhere on the paper. *sigh*

Obviously there's ee, CCcr, CC, TO?, and toto in the gene pool.

First question is saying in the modern herd, 11 out 90 horses are cremello. Assuming the herd is in Hardy-Weinberg equilibrium, what are the frequencies of the C and Ccr alleles?

Hardy-Weinberg equation is p^2 x 2pq x q^2

I know how to figure that out but she usually gives us the number of recessive (or in this case the chestnuts). And normally we figure out all three and not just two... Plus she's always given us examples where both homozygous dominant and heterozygous are the same colors and this is not the case with the cream gene.

If I calculated it right so far I have the frequency of cremellos at .34 and but I don't know how to figure out how many palominos and chestnuts are in the remaining 79.

Help?
The whole population starts as red, so assuming HWE remains, no new mutations appear, so every member of the final population will also be red. This narrows down how many genes you need to think about.

Are any of the questions to do with how many have inherited the pinto pattern? Because that is such a crappy way to run a genetics unit and not specify what pinto gene is there lol.

Ack this is the crappy lecturer that uses a different notation for cream, right? Which does she use to denote dominant and which for recessive?

Mods, grant me the serenity to see the opinions I cannot change, courage to change the ones that should change, and the wisdom to spot the trolls.
Chiilaa is offline
Old 11-30-2012, 11:11 PM
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No, that was mine, Chiilaa, but that's the same notation that doesn't make any freaking sense. Last time I checked, there was one "c" in the word "cream".
Poseidon is offline
Old 11-30-2012, 11:16 PM
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So, I am going to delve into this for you a bit. It's the first time I have ever looked at population genetics, so forgive me while I learn and make mistakes. I do, however, want to point out that HWE could not be established in this herd - inbreeding negates the "random mating" part of HWE, and with only 8 horses as your starting pop, it is inevitable they are inbred.

Mods, grant me the serenity to see the opinions I cannot change, courage to change the ones that should change, and the wisdom to spot the trolls.
Chiilaa is offline
Old 11-30-2012, 11:32 PM
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Ok, I cheated, but I have numbers!

I don't want to do your assignment for you, so PM if you need more help. However, your 0.34 frequency for cremello is off - that would be 34% of the population, and 11 is not 34% of 90.

Mods, grant me the serenity to see the opinions I cannot change, courage to change the ones that should change, and the wisdom to spot the trolls.

Last edited by Chiilaa; 11-30-2012 at 11:37 PM.
Chiilaa is offline
Old 12-01-2012, 09:12 AM
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Quote:
Originally Posted by Chiilaa View Post
So, I am going to delve into this for you a bit. It's the first time I have ever looked at population genetics, so forgive me while I learn and make mistakes. I do, however, want to point out that HWE could not be established in this herd - inbreeding negates the "random mating" part of HWE, and with only 8 horses as your starting pop, it is inevitable they are inbred.
Very true...the whole proplem is rather far fetched. The initial population is waaaay too low for Hardy-Weinberg to come into play, and 11 cremellos out of 90, considering the initial population, is rather absurd and totally negates "random" breeding. The problem can still be solved, but it is such a stupid problem it is beyond hypothetical...a professor ought to be able to come up with a more realistic problem than that...
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Old 12-01-2012, 11:24 AM
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Originally Posted by Faceman View Post
Very true...the whole proplem is rather far fetched. The initial population is waaaay too low for Hardy-Weinberg to come into play, and 11 cremellos out of 90, considering the initial population, is rather absurd and totally negates "random" breeding. The problem can still be solved, but it is such a stupid problem it is beyond hypothetical...a professor ought to be able to come up with a more realistic problem than that...
Yeah the entire thing is far-fetched...too many variables as well.

How many of those 82 new horses came directly from the first 8? How many of them came from the second generation breeding and so forth? You can't possibly determine the exact number and color of foals each horse produced (though since they're all red-based that would make it only slightly easier, but there's still the question of who bred who and what came out of it).

And 11/90 cremello. I'm assuming they're all solid cremello in the hypothetical problem, since the question didn't mention cremello pinto. Assuming that only the original 8 produced 82 new foals, that would mean the palomino pinto stallion would have had to breed with the palomino mare at least 11 times and successfully genetically combined for cremello foals. Ugh. This class would hurt my brain.

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Old 12-01-2012, 06:44 PM Thread Starter
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Originally Posted by Chiilaa View Post
The whole population starts as red, so assuming HWE remains, no new mutations appear, so every member of the final population will also be red. This narrows down how many genes you need to think about.

Are any of the questions to do with how many have inherited the pinto pattern? Because that is such a crappy way to run a genetics unit and not specify what pinto gene is there lol.

Ack this is the crappy lecturer that uses a different notation for cream, right? Which does she use to denote dominant and which for recessive?
-sigh- Yep...the same one. She does the CcrCcr (but the cr in superscript) for two cream, CCcr for one, and CC for none. Same one that still seems to think homozygous dominant roans are lethal.

There's more parts to the question (part A, part B, etc) it's just the first one that's asking about the cremello. I figure if I figure one out I can get the rest. One section asked about what red genes, creme genes, and tobiano genes are present. That's why I'm assuming all the "paints" have only tobiano. Plus that's the only one she put in her powerpoint "horse color instructional guide" for the students who don't know about horse colors. Just annoys me how she's teaching all these people the wrong things...though a large majority are horticulture people so they probably don't care anyway.

I'll probably PM you some more Chiilaa, just won't get around to working on it again until Sunday.

She is more into plant genetics so probably explains why this is so complicated. I might just try and fill it out and at least get some points for trying lol
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