Final answer:
Mendel stressed that heritable factors, now known as genes, retain their integrity across generations, with dominant and recessive alleles passed down from parents to offspring. His Law of Segregation delineates the conservation of genes even when phenotypes may temporarily mask recessive traits.
Step-by-step explanation:
According to Mendel, the heritable factors (genes) in pea plants are discrete units that control the inheritance of traits. Mendel's work emphasized the concept that these genes, whether they are mixed or temporarily masked, remain intact from one generation to the next. Despite the presence of different allele pair combinations, which can be dominant or recessive, the genes are passed on faithfully. This is clearly demonstrated through Mendel's Law of Segregation, which indicates that each parent contributes one allele for every gene to their offspring. Thus, even when a recessive allele is masked by a dominant allele in heterozygous individuals, it can still resurface in the progeny, as it is not lost but merely hidden. Mendel's repeated crosses gave a consistent 3:1 dominant-recessive ratio, supporting his postulation.