[tac] and [El Loco Pollo]:
Learn some GSD genetics before you next dream of attempting to answer this sort of question.
[ainawgsd]:
White is NOT "a recessive gene". See furtehr down.
Nor is white "recessive to all other colours" - its 2 gene pairs are epistatic to all other patterns & colours.
[winterru...]:
You'd have to provide a weird "diet" to drastically affect pattern & colour.
Okay, to the question:
Firstly, apart from possible white spots on toes, chest, and maybe tail tip, there will be NO black-&-white pups. The only such GSD pups are self-black descendants of Franka von Phenom who inherited her dominant mutation for "Panda"-markings.
Now learn how the self-black GSD and the self-white pooches are created.
In GSDs, all actual self-colours (whether black, liver or blue; white is not a colour, but a LACK of colour) are set by the recessive pairing a^ a^ in the Agouti Pattern series. The default colour from a^ a^ is self-black, but a pair of the recessive b^ in the Black-brown series will convert that to liver; a pair of the recessive d^ in the Dilute series will convert the black to the blue-gray referred to as blue. If the pup inherits both b^ b^ and d^ d^ the combined effect is a creamy-blue known as Isabella. (A pair of the b^ and/or d^ will also affect the dark area of dogs whose Agouti genes produce sable or saddle or bi-colour. Either pair also affects the colour of the "leathers" - eye-rims, nose, lips, pads.)
In all self-white breeds so far DNA tested the recessive pairing e^ e^ is present. But its effect is not to produce self-white, just to prevent eumelanin (dark pigment) from being formed by the hair follicles - something else has to block the phaeomelanin (tan pigment). However, as the factors for self-white behave as though they were a simple recessive, we can be sure that the second gene involved must be on the same chromosome as the e^, and located VERY close to it. In some breeds (eg, Samoyeds) the tan-blocker has been identified as the a^ a^ that produces recessive self-black, but there seems to be a different-but-not-yet-identified gene doing it in GSDs.
So your foolish plan is to be mate a self-black
(thus proven to be a^ a^ plus B^ ?^ plus D ?^ plus E^m ?^ plus ?^ ?^)
to a self-white
(thus proven to be ?^ ?^ plus ?^ ?^ plus ?^ ?^ plus e^ e^ plus Int^ ?^).
(PS: That E^m could be an E, but that is very unlikely in our breed.)
The ?^s are where you give us no evidence as to which allele of that series is present to make up the pair of alleles that every individual inherits in every gene location except on just the X chromosome. To work it out just remember that the series I am mentioning are A for Agouti, B for Black-brown, D for Dilute, E for Extension, and Int for Iljin's Intensity series. There are other colour series (you'll find all the known ones in the Files section of http://pets.groups.yahoo.com/group/The_G... but will need to become an instant-member, as Yahoo doesn't let me make that section "Public access") but they have no significant effect in your case.
From you, we have no idea what the self-white has in the Agouti series, but a many self-whites are genetically sables, so it is highly probable that he is A^w a^t (wolf-sable + saddle), very possible that he is a^t a^t. It's possible but unlikely that he is A^w a^ or a^t a^ - people who understand genetics do NOT want the genes from a self-white degrading the depth & shine of the self-black's all-over darkness, n or the all-over spread of eumelanin (dark pigment) making it harder for the e^ e^ to have its epistatic effect of blocking the eumalin (most whites have some "badger markings" where the phaemelanin (tan) wasn't completely blocked).
What it boils down to is that if the self-black is E^m e^ half the pups ( ± whatever random chance "decides" during the moments of fertilisation) will be self-white, about half won't. If the self-black is the E^m E^m that is preferred, all the pups won't be self-whites.
Either way, about half the pups are likely to be sables (assuming that the sire carries just one A^w) with the others probably being saddles. But they could ALL be saddles, or about half could be self-blacks. But if one parent is a self-black it is impossible to get all 3 of sables, saddles and self-blacks in the same litter, just any 2 of those. Of course, if the self-black dam carries an e^, about half the pups will look white and you won't be able to tell what pattern they are meant to be.
Regardless of their displayed colours, ALL the pups will be carriers of an a^ for self-colour from mum and an e^ for no-black from dad, plus are almost certain to have an Int^ or an int^ from dad.
The effect of Int^ or int^ will be that all the non-whites will have poor tans - from chalky "silver" to a washed-out creamy-fawn.
If the dam is carrying an e^, then about half the coloured pups will probably be "dirty yella dawgs" with no black - maybe when they're born, but definitely by the time they are about 2½ years old.
To complicate it:
Many of the people who produce pet-level self-whites are very happy to use carriers of liver or blue.
Although DogSport fanciers of blacks would avoid carriers of liver & blue, again pet-level BYBs might include them. So it's possible that the non-whites might be blue or liver instead of black where black should be in whatever their Agouti pattern is.
The possibilities are predictable (always allowing for random chance when the pairing at a locus is not homozygous), but you haven't given us evidence as to what alleles each parent is likely to possess, apart from the series that produced the black in one case, the white in the other case.
If your bit.ch were of breeding quality, you would be asking her breeder, not asking here where a high proportion of the so-called answers come from know-it-all kids pretending to be adult & expert.
If the stud you had in mind were of breeding quality, you would be asking HIS owner or breeder.
But in case I'm wrong about your bit.ch and that stud:
The ultimate proof of a GSD being of breeding quality is possessing a Breed Survey report (BS.Cl. in English, KKl. in German). No self-white is eligible for that, as all whites and blues and livers are disqualified in FCI#166: http://www.fci.be/uploaded_files/166A199... which is the ONLY GSD Standard approved by the WUSV (World Union of GSD Clubs, which has at least one seat-&-vote for every GSD nation and meets in conjunction with each SiegerSchau to sort out GSD issues).
But whatever the breed, the MINIMUM requirements for proving a medium-sized pooch breed-worthy are:
(1) recorded on the Breed Register without any limitations
(2) possesses official certificates for both hips & elbows
(3) possesses show certificates (placings or Excellent gradings) to prove that it looks typical of its breed.
Highly desirable are:
(4) a character certificate - BH or CGC
(5) a training qualification - for a GSD the ideal is HGH or SchH1, but all training qualifications prove that at least the pooch is highly willing to take notice of what its owner wants.
Sadly, almost every KC cares only whether both parents are in the same Breed Register - no checking on character or conformation or health or size or trainability...
Unless your bit.ch measures up, and so does the stud you choose to compensate for her flaws, forget about breeding from her.
And I haven't even touched on the financial risks every breeder faces.
Les P
owner of GSD_Friendly: http://pets.groups.yahoo.com/group/GSD_Friendly
"In GSDs" as of 1967