Is it possible ?

[Jelly]

Just seen an advert on a gundogs for sale site there was a advert which said the dam was a chocolate lab and the sire was a yellow lab and they had produced a litter of 9 black pups is this possible ?

[Sgurr]

Only if the yellow sire has a black nose

[Judy]

http://labbies.com/genetics.htm

[Sgurr]

There are 3 genes involved - B which is dominant Black, b which is Chocolate and the two forms of E (E and e) which modify the effects of B and b.
For the dam to be chocolate she cannot have the B gene so both her colour genes are b - bb - and to get the expression of the chocolate colour the pigmentation has to be modified by dominant E so she can be EE or Ee. As she does not carry the B gene the sire has to have it if the pups are black. The sire is yellow but has to carry black to give black pups. His B gene is modified by recessive e - and he has to be ee at that locus because an E there would make his coat colour black.
So the sire has to be eeBB or eeBb but all the pups are black so it is most likely that he is eeBB. He could be eeBb but it would be very long odds to get heads coming up 11 times in a row. So if the sire is eeBB he can only give a B gene to a pup and similarly an e. For the pups to be black, they have to have an E from the dam so she is most likely to be EEbb (again she could be Eebb but it's the eleven times in a row situation again and for it to happen from both parents.........)
With an eeBB sire (yellow coat colour but carries B) and a EEbb dam (chocolate) all the pups will be eEBb with black coats as the EB combination outweighs the effects of eb.
Or as I put it earlier, the yellow sire has to have a black nose.

[Stihl 090]

There are 3 genes involved - B which is dominant Black, b which is Chocolate and the two forms of E (E and e) which modify the effects of B and b.
For the dam to be chocolate she cannot have the B gene so both her colour genes are b - bb - and to get the expression of the chocolate colour the pigmentation has to be modified by dominant E so she can be EE or Ee. As she does not carry the B gene the sire has to have it if the pups are black. The sire is yellow but has to carry black to give black pups. His B gene is modified by recessive e - and he has to be ee at that locus because an E there would make his coat colour black.
So the sire has to be eeBB or eeBb but all the pups are black so it is most likely that he is eeBB. He could be eeBb but it would be very long odds to get heads coming up 11 times in a row. So if the sire is eeBB he can only give a B gene to a pup and similarly an e. For the pups to be black, they have to have an E from the dam so she is most likely to be EEbb (again she could be Eebb but it's the eleven times in a row situation again and for it to happen from both parents.........)
With an eeBB sire (yellow coat colour but carries B) and a EEbb dam (chocolate) all the pups will be eEBb with black coats as the EB combination outweighs the effects of eb.
Or as I put it earlier, the yellow sire has to have a black nose.

Well said Enid

[Judy]

Unless the dog is old in which case the black pigment might have faded to brown. The link I put up had a pretty picture of which colours can be carried by the black brown or yellows. I can cope wiv pictures!

[Jelly]

What colour would a yellow dam and a black sire produce?

[Sgurr]

Just go to Judy's link and work out the possibilities. Start with the pics which give the phenotype (colours) and the genotype (what genes they have) and its all there for you to work it out.

[Sgurr]

Judy, I was ignoring Dudleys and Silvers because I've not got my head around them yet - but yes I understand the pigments can fade - melanin and eumelanin - but how deep for an answer to a just curious enquirer?