I'm hoping there are some experts here. I've had a look at an old thread/same subject but the conclusion was unclear.

I've been looking at multiple genetic sites like https://www.vetgen.com/canine-coat-color.html and am further forward but still not absolutely clear in my mind how it all slots together.

Ok, a liver dog is bb. At least a bb dog will be liver coloured. But can a liver dog be anything apart from bb ?
Also the b is recessive so if for example a black was bred to a liver, the pups must be black ? Is that right ie Bb ?
So how do you get mixed litter's ? Even if you breed liver to black, the black would dominate hence black pups ? But I've seen mixed litter's so ???

The main question is the first - must a liver FCR always be bb ?

Thanks in advance

Edited too late !!

From http://www.doggenetics.co.uk/liver.html
This means that a liver puppy can be born from black parents if both are carriers of the liver allele (i.e. if both are Bb then at least one pup in four will be bb)

So a black with Bb can produce a liver - sort of got it. Bb times Bb = you can get bb
But
bb times bb = only bb puppies

So essentially any liver pups MUST be bb

You are correct :p liver is autosomal recessive so needs two copies of the recessive gene.

b/b is liver, will pass on liver
B/b is black, could pass on liver or black
B/B is black and will pass on black. This dog will never produce liver even if put to b/b.

"At least one pup in 4 will be liver" is of course nonsense, as they could all be black or all be liver.

Appreciate the reply and I think I understand it now.

For the situation I was interested in :
liver (bb) plus liver (bb) can only produce liver (bb) pups.

All sorted now. Thanks :)

But since yellow also exists (although rare and undesirable) in Flat Coats you could still get yellow as it is a different gene. If bb though they would all have brown noses even if they had a yellow coat.

There is a gorgeous golden flattie in our puppy class at the moment but she has a black nose :) lovely little thing.

Golden as in golden retriever colour ? Very unusual in the breed  as not accepted colour .although there was a group trying to breed them at one time I would love to see one  have only seen the odd picture.

Yep! She is stunning and her flattie feathers are just starting to come through. She is pure flattie and the owner has brought her because she is related to her foundation boy from over 18 odd years ago. I'll ask the owner if I can share a pic. The line has done well at crufts in recent years. She wasn't purposefully bred and is unlikely to be bred from.

There is a test for the recessive gene that carries yellow and both parents need to carry it for yellows to be born.
There is always a chance of them popping up in litters of untested parents and most breeders would sell them to pet homes, obviously cannot be shown, with breeding restrictions.

Yellow flatcoats are still lovely, and can be registered and worked, but as an 'unrecognised' colour won't  have any  luck in the showing as things stand at present.      The recessive e gene overrides B or b if it's  homozygous.    

The inheritance of the colours is effectively the same as Labrador colour genetics www.labbies.com/genetics.      It is possible to get other variations occasionally, influenced by genes on other loci, so you might get different shades of liver, for example, or possibly  brindling on the legs

Jo