The long bones are those that are longer than they are wide.
They are one of five types of bones long, short, flat, irregular and sesamoid.
When two parents are purebred it means that they are homozygous for the characteristic that's being tested (in this case the fur colour). When they are crossed, the offspring will obligatory be heterozygous, an allele of each type from its parents. So, the trait that comes up will be the dominant trait, while the recessive trait will be hidden.