Try as I may the cat genetics still goes over my head slightly.
I know both parents have to carry a colour locus for a pup to be that colour - but my question is to do with the likelihood of a dog carrying a D locus. The dogs paternal grandmother carried it - so what would the chances be of her grandson carrying the locus? what percentage usually inherit the carrying of a gene?

I am absolutely rubbish with maths ad statistics, so hopefully someone else can oblige with the probabilities.

If you have a carrier of a recessive such as D, then when they are bred to a non carrier, 50% will also carry the gene. So it's a 1 in 2 chance that the dog kept from that litter and bred on with, carries it.

If it doesn't,  then the gene stops there.
If it does, then again, there's 50% again, 1 in 2.

Repeat for all the ensuing generations.

A DNA test for dilute is probably your best bet!

Have had a think and looked up probabilities. As there is a 1 in 2 chance, it's the same as tossing a coin, as there are only two outcomes - carrier or non carrier, same as Heads or Tails.

The dog's paternal grandmother did carry the gene - I am hoping here she was a carrier rather than actually Dilute herself, as this would change things. To produce the dog's sire, the coins were tossed once, giving a fifty-fifty chance of the sire inheriting the gene.

Then the sire was bred to the dog's dam, again 50/50... BUT we are looking at the probability here of both the dog's sire, AND the dog himself inheriting the gene, which is the same as the chance of tossing two Heads in a row.

That works out as 1 in 4, or 25%.

thank you :-)

yes, Studs Paternal grandmother a carrier not dilute herself. My bitches mother was a dilute and I know my bitch carries dilute.