Final answer:
Approximately 50% of the meiotic products will result in nonviable gametes when crossing over occurs in a paracentric inversion loop during meiosis, due to the production of gametes with structurally abnormal chromosomes.
Step-by-step explanation:
When crossing over occurs during meiosis in a paracentric inversion loop, it can lead to the production of gametes with inviable chromosomes due to acentric fragments (those lacking a centromere) and dicentric fragments (those with two centromeres). During anaphase, these abnormal fragments are typically not incorporated properly into the daughter cells, leading to genetically unbalanced gametes. Since crossing over in a paracentric inversion affects two out of the four chromatids, it is generally expected that 50% of the resulting meiotic products will be nonviable.
The genetic consequences of meiosis I involve recombination of maternal and paternal genes during crossover events in prophase I, as well as the random assortment of chromosomes during metaphase, both contributing to genetic diversity. However, a paracentric inversion can disrupt this process, leading to a significant portion of gametes being nonviable. Moreover, nondisjunction, whether it occurs in meiosis I or II, can also result in abnormal gamete formation, though it affects all meiotic products differently from a paracentric inversion.