| T O P I C R E V I E W |
| Charles |
Posted - 03/10/2012 : 21:05:49
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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| 20 L A T E S T R E P L I E S (Newest First) |
| eeji |
Posted - 27/10/2013 : 21:41:48
thats correct, "super" is a trade name used for homozygous codominant morphs |
| Razee |
Posted - 27/10/2013 : 21:28:45
P.S. Sorry if I'm a pain, I just find it really interesting. |
| Razee |
Posted - 27/10/2013 : 21:27:50
I see, thanks for that -that's interesting. So, there is no "super" form ( as there would be in royals - two copies of pastel gene = super pastel , etc ). |
| Charles |
Posted - 27/10/2013 : 19:36:24
I have just been discussing this with multicorn today. Although some claim that you can visually tell the difference between het and homo tessera he is not convinced. If he is right then you are correct the only way to be sure with an unknown tessera is breeding. As gmac said, if it is homo then the young will all be tessera. if it is het then 50% will be. |
| Razee |
Posted - 27/10/2013 : 19:21:33
Confused now 
I understand the co - dom / dominant bit, but does that mean, that if you have a visual tessera, you don't know, if it is a het or 100% ( homo ) tessera, because both are visually tessera? So, the only way to find out, would be by test breeding it to a normal corn?
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| gmac |
Posted - 27/10/2013 : 18:50:42
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. |
| Charles |
Posted - 27/10/2013 : 18:40:25
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. |
| serena_08 |
Posted - 27/10/2013 : 18:01:46
Very interesting, I do not understand a single thing anyone has said! Lol |
| Razee |
Posted - 27/10/2013 : 17:28:21
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 :-) ) |
| Charles |
Posted - 27/10/2013 : 16:49:54
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 |
| eeji |
Posted - 27/10/2013 : 15:43:38
a new project that may help.... http://iansvivarium.com/punnett
[/plug]  |
| Charles |
Posted - 27/10/2013 : 13:05:58
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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| eeji |
Posted - 06/10/2012 : 18:35:59
motley and stripe are different mutations of the same gene |
| gmac |
Posted - 05/10/2012 : 22:21:43
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. |
| Charles |
Posted - 05/10/2012 : 22:14:29
I suppose that is true. I wonder what the Correct term is? Co-recessive? Seems unlikely, will have to research. |
| gmac |
Posted - 05/10/2012 : 21:24:28
stripe and motley arent co dominant they are both recessive, but share the same place on the gene ladder. |
| Charles |
Posted - 05/10/2012 : 15:33:12
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. |
| eac84 |
Posted - 05/10/2012 : 09:59:46
you should do more of them mate |
| Isoldael |
Posted - 05/10/2012 : 09:25:35
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 |
| Charles |
Posted - 04/10/2012 : 23:10:56
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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