Final answer:
The trait for white fur is considered a recessive allele and may still be present in a black-fur hybrid but hidden due to the dominance of other alleles. By looking at inheritance patterns and through controlled breeding experiments, it can be determined whether the white fur trait is present and can be passed on to offspring.
Step-by-step explanation:
To determine if the trait for white fur is still present in a black-fur hybrid, we must look at the principles of inheritance, specifically the concept of dominance and recessive alleles. In cases where there are multiple alleles and a hierarchy of dominance, the presence of a recessive trait can be masked. In Rabbit coat color genetics, for instance, there are multiple alleles that contribute to different phenotypes. The wild-type allele (C+) is dominant over all others and results in brown fur. The chinchilla allele results in black-tipped white fur and is incompletely dominant over the Himalayan phenotype, which has black fur on extremities and white elsewhere. The albino phenotype (cc) results in white fur and is recessive.
If we cross two heterozygous organisms (C+c), the recessive c allele responsible for white fur in a homozygous organism (cc) may still be present in the hybrid but not expressed. This is due to the dominance of the C+ allele. When examining offspring ratios, particularly in an F2 generation (from crossing two F1 hybrids), Mendelian genetics predicts the recessive white phenotype will reappear according to a 3:1 ratio if both parents carry the recessive allele.
The presence of the recessive trait can also be determined through controlled breeding experiments or genetic testing. In summary, while a black-fur hybrid exhibits the dominant phenotype, the alleles for white fur can remain hidden within the genetic makeup and can be passed to the offspring, revealing the trait under specific breeding scenarios.