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Gene interactions

1075 Views 5 Replies 3 Participants Last post by  Jack Garcia
Heya, i'm doing my Breeding and Genetic assignment for college at the moment, and i'm getting a bit stuck ):
Can anyone give me examples and definitions (if possible) for Imcomplete dominance and Co dominance. Could i use sealpoint siamese x blue= blue siamese as an example for one of them?

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At the risk of stating the obvious: tan?

I don't know what the difference is between incomplete and co-dominance though. I'd be interested to hear an explanation too - I tried to suss it out once but I just confused myself!
haha, my tutor explained it but i didn't take notes D:
i shall ask her about it on monday

Yeah i think tan is co-dominance, but i'm not 100% sure.

I know that incomplete dominance is when there is a dilution between two colours or body features, so could ear size count? like, breeding large eared mouse with a small eared mouse?

And co-dominance is when two genes don't show any dominance over eachother. (eg. wall eye in some animals)
But can't really think of anything mousey related ):
from this website (which I hope is ok to post since it's educational and isn't selling or promoting anything): ... e00783.htm

Codominance - A form of inheritance in which both alleles
are equally shown.

Blood typing is a great example.
AB blood is the codominant relationship between the A protein and B
protein both expressing themselves completely.
AO (type O allele means there is no protein), A is dominant and you
see type A phenotype.
BO is the same except you see the B phenotype. Type O is recessive.

Incomplete dominance - A form of inheritance in which the
heterozygous alleles are both expressed,
resulting in a combined phenotype.

The one example that most books
give is seen in some flower colors.
A red and a white allele gives pink. If it were codominance, you
would see the red and white colors.
Incomplete dominance is most commonly found in plants.
So himalayan (ch) and beige (ce) would be an example of incomplete dominance--both are expressed visually when present on the same mouse.
jack, could you confirm the following (think you have a better idea than i do)

sealpoint siamese X blue = Blue siamese
Is this incomplete dominance?

And is things like ear size,eye size and deepness of colour (light chocolatex dark chocolate= the medium) co-dominance?
ps thanks for the help :p
Sealpoint siamese X bluepoint siamese = 100% sealpoint siamese, unless the sealpoint parent is carrying blue. Siamese (ch/ch) is separate from blue (d/d) so it's neither incomplete dominance nor co-dominance because those terms refer only to alleles situated on the same locus. The C-locus (where siamese sits) is the most complicated in mice. The D-locus (where blue sits) is one of the simplest.

For a moment, pretend that you are dealing with siamese and beige, which are on the same locus, the C-locus. In simple terms, when a siamese (ch/ch) is bred to a beige (ce/ce), you will get a whole litter of mice who are ch/ce. In this case, siamese is incompletely dominant to beige because you can see both phenotypes. You could equally say that beige is incompletely dominant to siamese.

Now pretend that you are dealing with a wild agouti (A/A D/D) mouse and a blue mouse (a/a d/d). When bred together, you will get all agouti mice (A/a D/d) carrying blue but when speaking of the blue-locus this is technically neither incomplete dominance nor co-dominance. It is simple (aka Mendelian) dominance. The A is dominant to the a. The D is dominant to the d. The A cannot really be said to be dominant to the D or d because they're in different locations (loci).

Things like ear size and placement, tail set-on, deepness of color, etc., are termed polygenetic which means they are controlled by alleles of multiple genes, some of which are always inherited together and some of which are not. And each of these alleles my have modifier alleles (commonly called simply "modifiers") in other places on the same chromosome (linked) or a different chromosome, which help push the phenotype a little bit in one direction or another.

With that said, there is no "proper ear placement" gene that makes the ears sit correctly; there is no "rich deep reddish-brown chocolate color" gene that makes a chocolate the right shade; instead there are numerous factors involved all at once and it's as much a game of luck as one of skill when you do get a line of mice who have nice ears (or tail, or whatever). This is why it's so much easier to breed pet-type mice and concentrate primarily on the color--color is usually determined by only one or two genes. It's much harder (but more rewarding, imo) and takes much more time and work to concentrate on type, temperament, and color for show. When you're breeding professional for show you're literally dealing with dozens of different variables, only a few of which have been scientifically measured, mapped-out, and assigned a letter (such as the A locus, B locus, etc).

P.S. You're very welcome. Mouse genetics is my major area of interest in life (gee, that makes me sound so boring) and I love helping people. lol :p

If you cite me, please use this format:

García, J. (2010, March 12). Re: Gene interactions.

Retrieved March 12, 2010, from Fancy Mice Breeders website:

http: //w ww.fancymicebre
(but remove the spaces in the url)
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