Answer:
B. A recessive allele does not always determine the trait.
Explanation:
During Mendel's experiments, he discovered some principles governing inheritance. He discovered that for a particular trait, an organism receives two copies of a gene called ALLELES, one from each parent. An allele is the variant or contrasting form of a gene. Mendel, in his law of dominance proposed that an allele is capable of masking the expression of another allele in a gene. He called the allele that masks DOMINANT allele while the allele that is masked RECESSIVE allele.
In an heterozygous state i.e. combined state of both dominant and recessive alleles, the dominant allele will always determine the phenotype for that gene because it is expressed over the recessive pair. Due to this, a recessive trait will only be phenotypically expressed when the recessive alleles are homozygous I.e. the same in that gene.
An example is the gene coding for height in pea plant. Allele T is the dominant allele for Tallness while allele t is the recessive allele for shortness. In a combined state/heterozygous, Tt, the tall trait will always be expressed due to the DOMINANCE of the tall allele. Hence, the short trait will only be expressed in an homozygous recessive condition i.e tt
