Final answer:
Concordance rates never equal 1 due to genetic diversity from sexual reproduction, variations in meiosis, influences of chance in Mendelian inheritance, and environmental factors affecting gene expression.
Step-by-step explanation:
Concordance rates are never equal to 1, other than due to epigenetics, because of several biological factors:
- Each human couple has the potential to produce more than 64 trillion genetically unique children due to the immense variations created through sexual reproduction, making perfect genetic concordance practically impossible.
- During meiosis, it is highly unlikely that any two haploid cells will have the same genetic composition, which contributes to genetic diversity.
- Mendelian inheritance and the influence of chance events can significantly affect genetic outcomes. For example, parents heterozygous for a recessive genetic disorder may have offspring with varying presence of the disorder, despite the predicted ratio of inheritance.
- Environmental factors
These mechanisms, including the random assortment of chromosomes, varying gene dominance, and gene-environment interactions, all lead to variability that prevents concordance rates from reaching 1.