* Genetics: Labrador coat color is determined by two genes: the "B" gene for black pigment and the "E" gene for the expression of pigment.
* B gene: A dog can have BB (black), Bb (black), or bb (chocolate) for this gene.
* E gene: A dog can have EE or Ee (pigment is expressed), or ee (pigment is masked, resulting in yellow).
* Parent combinations: A chocolate Labrador must have the bb genotype. A yellow Labrador can have either Ee or ee genotypes.
* To produce a black puppy, at least one parent needs to contribute a "B" allele. Since the chocolate parent only has "b" alleles, it's impossible for them to pass on a "B" allele.
In summary: While it's technically possible for a rare genetic mutation to occur, it's highly unlikely that a chocolate and yellow Labrador pairing would produce a black puppy.