Answer: The genotype must be a homozygous recessive allele.
Explanation: A recessive allele is a gene which lacks the ability to manifest itself outwardly in the presence of a dominant gene. A homozygous allele is a pair of gene made up of two identical genes which can either be recessive or dominant. Examples of a homozygous allele is AA, aa, BB, bb.
For a recessive allele to manifest outwardly, it must be homozygous for example aa, bb, tt. If a recessive allele is heterozygous such as in Bb, (b) which is recessive will not be able to express itself phenotypically because the dominant allele (B) will overshadow its effect.