For each of the genotypes below determine what the phenotype would be. Bobtails in cats are recessive. Normal tails are dominant. TT _ Tt tt ____
The Correct Answer and Explanation is:
In the case of Bobtail cats, the gene for the tail length follows simple Mendelian inheritance. The allele for a normal tail (T) is dominant, while the allele for a Bobtail (t) is recessive. This means that an individual must inherit two copies of the recessive allele (tt) to have a Bobtail. If they inherit one or two copies of the dominant allele (T), they will have a normal tail.
Here are the genotypes and their corresponding phenotypes:
- TT: This genotype consists of two dominant alleles for normal tail length. Since the dominant allele T masks the effect of the recessive allele t, a cat with the TT genotype will have a normal tail. There is no possibility for a Bobtail phenotype because the presence of two dominant alleles overrides any potential recessive traits.
- Tt: In this genotype, the cat has one dominant allele (T) and one recessive allele (t). The dominant allele T will determine the phenotype, meaning that the cat will also have a normal tail. The recessive t allele is still present, but it does not affect the phenotype unless the cat inherits two copies of the t allele (tt).
- tt: This genotype consists of two recessive alleles for Bobtail. Since there are no dominant T alleles present to override the recessive t alleles, the cat will have a Bobtail. This is the only genotype in which the recessive Bobtail phenotype is expressed, as the recessive alleles need to be homozygous (tt) to show their effect.
In summary, the phenotype of the cat is determined by the interaction between the dominant and recessive alleles. A TT or Tt genotype results in a normal tail because the dominant T allele masks the effect of the t allele. A tt genotype, however, results in a Bobtail because both alleles are recessive and the dominant T allele is absent. Thus, only a homozygous recessive (tt) genotype can produce a Bobtail phenotype.
