Ive been put in charge of the rat breeding program at work and had to pick out of all the rats who were to be kept and who was to be found pet homes. The person who was breeding them befor they came in was doing it manly for colour as they wanted a solid blue rat (all but one are blue and white). I have picked 3 sisters who were born after they came in so im some what attached to them but the main reason i want to keep them is because of there temperment, all the other rats will bite if u poke your fingers through the bars but not these 3 girls and they never nip or anything and i want to breed for temperment first (none of them have any health prolems). out of the males ive picked a male with the best temperment and the other male was picked for me as the man in charge wants to keep and breed the brown male as he is a difrent colour to the rest.

Ok now the problem, i dont like the brown males temperment he is friendly to people (allthough he is a bit shy) but he is very selfish and bossy with the other rats and can be short tempered. if i put in a big treat with the other rats they will share it but with the brown male even looking at his treat will start an argument. So i have 2 males and 3 female. out of the girls one has a perfect temperment and is exactly what i want friendly not agressive, nervous, or pushy or in your face or jelous and is what i would call polite (she waites to be told or invited to play or come out) one of the sisters is a little more shy than i would like and the other is a little more pushy than i would like and she gets jelous if im giving attenton to someone else (i spoilt her when she was a kit). So i would like to breed the sister with the best temperment to the male with the best temperment and only breed one of the sisters to the brown male, but i cant decide which one.

Do i breed the pushy one with a bit of a jelous streak to the brown male who is pushy with other rats and gets jelous and risk getting a litter of pushy kits or do i breed him to the sister who is more shy hoping that the kits come up less nevous than her but not as pushy as him or. I think temerment is made up of both genetics and enviromental factors so i want to get both as good as possible. They want him bred so which one should i match him to? at the moment im thinking of breeding him to the shyer one.
But they wont want anything bred untill the new term starts so ive got a while to think it over.

can i ask why your breeding them? how many do you intend to keep? SS

I no when I bred rats the mom was pretty nippy but none of the babies were- I handled them from birth once a week till they got a lil bigger, then I handled them every day. When you put your hand in the cage they would climb on you and lick you, reminded me of puppies. The dad had an excellent temperment just loved cuddles. I personally think alot has to do with how they are raised. I even had the mom raise to pinky mice and kept the lil girl in the same cage with her and put the boy with the boy rats and dad.

How old is the brown (I take it he is Mink or perhaps Agouti?) male? He may be going through 'teenage' aggression/hormonal issues, and to be honest males that do this aren't always the best choice as their sons are likely to follow suit. If he is older than that and is still aggressive to other rats then even more reason to be cautious. 
What colour is the other male?
If you want to breed a solid blue, then the brown will not be a good choice anyway. Do you know which kind of blue the rats are? One gene for blue in rats has some health issues attached to the colour, with extra risks for females.

they breed them at work, its a college that runs animal courses. We have (well will have after i rehome 3 males and 2 females) 3 females and 2 males.
Not keeping the 3 males as 2 are the girls full brothers from a previous mating and dont want to split up the group, and one of the female in the pair has shown agression.

not sure how old he is as he was adult when ther came in, so maby 1year (i know he sired browns, brown and white, grey and white and champain). The other male is blue and white.

No not sure realy, one is more of a blue roan and white, Ive been trying to find info on colour genetics for rats but had no luck, (i did a bit of hourse and dog in college). Im planning to buy in new rats for the next generation when ive picked the keepers from the litters i want to advoid inbreeding them. Relay im not that fussed on getting a solid but thought i would keep the colour going provinding i dont have to sacrifice temperment or health.
I would love to know about the helath issues with one of the blue genes if you could tell me more.

Sounds bad but i dont realy know that much about rats as i didnt like them untill the 3 girls came along, so since iv peen put in charge im doing as much research as possible befor breeding.

i have some photos ill upload them.

The more pushy girl
http://i199.photobucket.com/albums/aa236/kentanstormcracker/Work/Chihuahua-2.jpg
The girl with the best temperment
http://i199.photobucket.com/albums/aa236/kentanstormcracker/Work/Chihuahua-1.jpg
The more shy one
http://i199.photobucket.com/albums/aa236/kentanstormcracker/Work/Chihuahua.jpg

There parents
http://i199.photobucket.com/albums/aa236/kentanstormcracker/Work/benjibanner-1.jpg
http://i199.photobucket.com/albums/aa236/kentanstormcracker/Work/benjibanner.jpg

The boys
http://i199.photobucket.com/albums/aa236/kentanstormcracker/Work/Gblock029.jpg
http://i199.photobucket.com/albums/aa236/kentanstormcracker/Work/Gblock028.jpg

im planning to allways have 3 females and 2 males so work dont get over run with rats again, there were a few litters when i started and most went to homes with students and there friends and family and some went to a petshop where one of the students works.
Allthough there are also snakes at work who eat rats. this may some realy bad to some people but they have to buy in frozen rats from a seller and they have no idea how the rats were kept or killed (thy could be cramped in tiny cages for all they know) so if they were to breed there own rats and mice to feed the snakes at least they know they were given the best of care and attention and killed humanly.

Hi Have pmed you x

Your rats are Roans (sometimes also called Husky) - more correctly, striped Roans and I'm afraid they can't be bred as solid Roan, as the gene is linked to a white pattern. They can start off any known rat colour (though black or agouti are the most usual) then acquire their roaning at about 6 weeks when the baby coat moults out. They then become progressively lighter as they age (rather like Grey horses) and usually end up totally white.

This is a good place for some background to genetics:
http://www.hawthorn.org.uk/articles/genetics.html
also
http://www.ratz.co.uk/genetics.html
It is best to choose UK based sites for rat genetics as they differ from country to country (as do variety/colour names). There is also a Ratgenetics yahoogroup which has colour genetics experts from various places worldwide.