Final answer:
Mary's mom attributes Mary's tallness to genetics, implying that the trait for height has been inherited from her father, who is also tall. This is based on Mendelian genetics, where tallness as a dominant trait can be passed on to offspring.
Step-by-step explanation:
The explanation given by Mary's mom emphasizes the effect of genetics on Mary's height. From the principles laid out by Gregor Mendel, we understand that traits like height are influenced by alleles, which are different forms of a gene. If one parent has a dominant allele for tallness, this trait can be passed down to the offspring, making them more likely to be tall if tallness is indeed the dominant trait. Genetic inheritance, not random chance, is the primary factor highlighted in this scenario for explaining Mary's tall stature.
Additionally, while environmental factors like nutrition can play a role in an individual achieving their full potential height, the predominance of tall genes inherited from a tall parent is a major determinant in this context. In the example of pea plants, a dominant allele for tallness (T) would result in the expression of the tall phenotype, even when paired with a recessive allele for shortness (t).