True or false: if black coat color is dominant to brown coat color, in a heterozygote the black allele will destroy the brown copy of the gene.

False. The allele conferring the black colour to the coat won't destroy the other copy of the gene conferring the brown copy as in heterozygous there is an allele (in this case, the one conferring the black colour) that is dominant over the other. This means that the earlier will not destroy the latter, but will, instead, overrun it making its genetic information prevail over the recessive allele's genetic information (brown).