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Charles
Hatchling
United Kingdom
229 Posts |
 Posted - 03/10/2012 : 21:05:49
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So I am a Biology teacher and I have put the research I have done when looking to buy Rosie to good use. please find attaached a question I have made foe my A level class. i hope it passes muster.
North American Corn snakes are a popular pet due to the fact that they are easy to keep and come in many different patterns (morphs) due to selective breeding. The main colours on a wild type snake are a red and black. Two recessive mutations exist, one for each colour.
• Amel cannot make the black pigment melanin. They are known as Red Albinos
• Anery cannot make the red pigment red pigment erythrin. They are known as Black Albinos.
A snake that can’t make either red or black pigment is known as a Snow.
1. A breeder has bought a true breeding male amel and a true breeding female anery. How could he use these snakes and their offspring to produce a snow morph? Show your working and comment on how easy it would be to get a snow from these snakes.
2. In the F1 generation the breeder was surprised to see some anery morphs. Suggest how this happened.
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1.1.0 Jim Caramel Tessera, Rosie Motley
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jenjen23
Hatchling
United Kingdom
157 Posts |
Posted - 03/10/2012 : 21:18:30
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Looks good, i'm a plant geneticist so hopefully what I know applies! By true breeding do you mean homozygous? If so, all offspring would be heterozygous for both mutations, these hets could then be crossed to produce 1/16 snow (double mutant for both genes). Recombination (crossing over) to produce the anerys in F1?? (I expect the A level students will beat me on that one!)I hope that is right, wake my brain up this evening at least  |
0.0.1 Normal Cornsnake, 2 years old - Basil
0.1.0 Crawl Cay Boa, 1.5 years - Luna |
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Moppet
Fully Grown Corn
United Kingdom
3315 Posts |
Posted - 03/10/2012 : 21:32:05
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I like it 
I guess showing your working would be a punnett square (well, two in this case, one for F1 and one for F2). Both parents bred together will give 100% chance of normal heterozygous for anery and amel. Breeding two of those (F1) together would give 25% amel, 25% anery, 50% snow (this would be F2)? Tried to do a punnet square in my head haha, that could be horribly wrong (EDIT: It was horribly wrong! See my later post for a better attempt which I just couldn't manage in my head haha) . In theory (EDIT: which was wrong :S) I guess half the hatchlings of the F2 generation would be snows. But we all know it doesn't always work out that way haha.
As far as I understand it, F1 is the result of breeding the first set of snakes together (these are sometimes known as P), so there could be anery morphs in F1 if the amel (P) was heterozygous for anery. |
2.4.0 Corn snakes
1.0.0 horse
0.1.0 Golden retriever
1.4.0 Guinea pigs |
Edited by - Moppet on 03/10/2012 22:40:20 |
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gmac
The Scottish Admin
United Kingdom
5319 Posts |
Posted - 03/10/2012 : 21:45:46
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the percentage of snows will be less than that of the single traits ;) and you wuold also get normals from the offspring breedings. (unless he bred 2 aneries)
Also hope they dont have access to smart phones or the working could be print outs from corncalc hahaha.
also the % of morphs per breeding is %chance per egg no guarantees on actual numbers |
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Moppet
Fully Grown Corn
United Kingdom
3315 Posts |
Posted - 03/10/2012 : 22:37:15
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I thought my results sounded a little strange to be right. Hmmmm. I think my second punnett square was screwy. Didn't put anything for the 'normal' part of the snakes, just put the hets in. Can't seem to make a punnett square work for a double het animal. Hang on, I think I remember this from A level, maybe.
Need to do the possibilities from each parent first, then put them in a punnett square. So this time I got 1/16 normal no hets, 2/16 normal het anery, 2/16 normal het amel, 1/16 anery, 4/16 normal het anery amel, 1/16 amel, 2/16 amel het anery, 2/16 anery het amel and 1/16 snow! That sounds much better.
So phenotypes would be 9/16 normal, 3/16 anery, 3/16 amel, 1/16 snow if I have got it right this time
It's much easier to use the corncalc  I do love to work it out though, it is kinda fun. |
2.4.0 Corn snakes
1.0.0 horse
0.1.0 Golden retriever
1.4.0 Guinea pigs |
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eeji
The Morph Master
United Kingdom
4335 Posts |
Posted - 03/10/2012 : 23:21:46
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just one tiny (pretty insignificant) comment on the original question, red albino and black albino are terms that are very rarely used, other than that all good stuff
...and anyone using the corn calc for this one is just cheating Its a good thing to learn this sort of stuff because it helps people understand how and why the predicted outcomes are what they are instead of just grabbing a list of morphs from t'internet, and makes the whole breeding game a lot more interesting. |
Forum - Guide to Cornsnake Morphs - Punnett Square Calculator - Breeder Directory
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Charles
Hatchling
United Kingdom
229 Posts |
Posted - 04/10/2012 : 23:10:56
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Did with one of my classes today - it went well, apart from the typos not spotted until after photocopying
All F1 would be heterozygous normal.
F2 9:3:3:1 Normal:Amel:Anery:Snow
So snow would not be common. Part 2 is typical exam trick. I just wanted that one of the parents was not homozygous for the dominant trait.
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1.1.0 Jim Caramel Tessera, Rosie Motley
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Isoldael
Yearling
Netherlands
999 Posts |
Posted - 05/10/2012 : 09:25:35
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I'd probably just cheat and assume the anery was het for amel, and the amel het for anery. You could already produce snows in the first breeding then :P
Also... in the second question. You said you wanted one of the parents not to be homo for the dominant trait. You do know that neither anery nor amel are dominant right? So they would always have to be homozygous for anery or amel to show that. They could, of course, be het for another trait in addition to the genes that determine their phenotype...
Okay, now that I typed this, I'm not sure it makes sense anymore :D |
1.0 anery stripe (Nash)
1.0 hypo pewter (Loki)
1.0 bloodred het amel, charcoal, hypo, stripe 50% phet anery, lavender (Kasumi)
0.1 grey background normal het amel (Saphira)
0.1 tessera het amel, anery, stripe (Lilith)
0.1 amel (Aurora)
0.1 hypo bloodred het anery, charcoal, stripe 50% phet amel, lavender (Mara)
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Edited by - Isoldael on 05/10/2012 09:28:41 |
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eac84
Egg
United Kingdom
70 Posts |
Posted - 05/10/2012 : 09:59:46
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| you should do more of them mate |
Euan
1.1.0. normal stripped, normal corn 0.1.0 e.s.s |
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Charles
Hatchling
United Kingdom
229 Posts |
Posted - 05/10/2012 : 15:33:12
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There are some co-dominant like strip/ motley that could. E interestIng. I was hoping for some linked or epistatic interactions. However none seem to be described yet.
Was too tired this morning to check the 2nd question. Answer wanted was original male is Amel het anery. |
1.1.0 Jim Caramel Tessera, Rosie Motley
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gmac
The Scottish Admin
United Kingdom
5319 Posts |
Posted - 05/10/2012 : 21:24:28
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| stripe and motley arent co dominant they are both recessive, but share the same place on the gene ladder. |
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Charles
Hatchling
United Kingdom
229 Posts |
Posted - 05/10/2012 : 22:14:29
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| I suppose that is true. I wonder what the Correct term is? Co-recessive? Seems unlikely, will have to research. |
1.1.0 Jim Caramel Tessera, Rosie Motley
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gmac
The Scottish Admin
United Kingdom
5319 Posts |
Posted - 05/10/2012 : 22:21:43
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| motley is accepted to be dominant over stripe so het motley stripe will show as visual motley generally. but both just recessive genes in the end. |
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eeji
The Morph Master
United Kingdom
4335 Posts |
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Charles
Hatchling
United Kingdom
229 Posts |
Posted - 27/10/2013 : 13:05:58
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OK - another year and another snake have caused be to write a second part to the question:
Two other mutations are:
• Tessera is a pattern mutation leading to a strip down the snakes back.
• Caramel snakes don’t produce a red pigment, but develop a yellow and brown colour. It is recessive.
3. A true breeding wild type is crossed with a tessera. The offspring are 50% wild type and 50% tesserae. What information does this tell you about the inheritance of tessera? Show your working.
4. Mr Whiteley has two snakes. The male, Jim, is homozygous for caramel and heterozygous for tessera. The female, Rosie, is heterozygous for Caramel. Complete a Punnet square to show the ratio of the phenotypes that would be produced if they were crossed.
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1.1.0 Jim Caramel Tessera, Rosie Motley
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eeji
The Morph Master
United Kingdom
4335 Posts |
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Charles
Hatchling
United Kingdom
229 Posts |
Posted - 27/10/2013 : 16:49:54
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I just tried it out and it works very well. I like the way it reduces the complexity when it can.
However, the students have to be able to do it the old fassioned way - poor things |
1.1.0 Jim Caramel Tessera, Rosie Motley
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Razee
Fully Grown Corn
United Kingdom
2525 Posts |
Posted - 27/10/2013 : 17:28:21
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| Question: I thought tessera is a co - dominant morph, so when you cross tessera and normal, 50% babies will be tessera, 50% normal. If it is so, then there shouldn't be such thing, as heterozygous for tessera - if the gene is there, it's expressed, if not, the baby is just a normal,with no tessera gene? ( just to be awkward :-) ) |
0.1.0 late CB10 Carolina corn snake - Bazilishka
1.0.0 CB11 Abbots Okeetee- Little Twiddler
1.0.0 CB11 Hypo corn- Sebastianek
1.0.0. CB14 Butter Motley - Squidwood
0.0.2 CB18 normal/ Okeetee yearlings Bunny and Lalalishka
0.0.1 hognose
0.1.0 stable cat
0.1.0 house cat |
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serena_08
Yearling
United Kingdom
784 Posts |
Posted - 27/10/2013 : 18:01:46
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| Very interesting, I do not understand a single thing anyone has said! Lol |
1.0.0 Corn: D-Bo (Amel)
1.0.0 Western Hognose: C*ntyB*ll*cks
0.1.0 MBK: Rosa
0.0.1 Leopard Gecko: Zuko
0.0.1 Bearded Dragon: Kobe
0.0.1 Fire Bellied Toad: Snoop
1.1.0 Cats: Penny and Sheldon
1.0.0 Staffy: MooMoo
I intend to live forever. So far, so good. |
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Charles
Hatchling
United Kingdom
229 Posts |
Posted - 27/10/2013 : 18:40:25
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Teacher mode on
Razee - heterozygous and homozygous describe the copies of the specific gene the animal actually has. If you have two copies of the same version of a gene (allele) then you are homozygous; if you have two different versions you are heterzygous.
co-dominant means that if you have two different versions of the same gene then both traits are visable, either seperatly or blended. E.g. in blood groups gene version A and gene version B are codominant so if you are heterozygous you have blood group AB. In snap dragons the colour red and white are codominant. If a flower has a copy of the red version of the gene and the white version of the gene then it is pink!
I would describe Tessera as dominant to normal and therefore it is possible to be homozygous for tessera.
Teacher mode off
Things will get confusing if people loose track of whether their snakes are het tessera. In fact this conversation has just caused me to double check about Jim. |
1.1.0 Jim Caramel Tessera, Rosie Motley
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gmac
The Scottish Admin
United Kingdom
5319 Posts |
Posted - 27/10/2013 : 18:50:42
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Tessera is dominant not codom, you could say het tessera will produce 50% tessera hatchies, whereas hom tessera would pproduce 100% tessera hatchies.
Het tessera still being visual though. |
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Genetics Question
