Final answer:
During meiosis, crossing over can occur in a paracentric inversion loop, potentially leading to nonviable gametes. The percentage of nonviable gametes depends on the location and size of the inversion, as well as its effects on gene function.
Step-by-step explanation:
During meiosis, crossing over occurs when homologous chromosomes pair and exchange genetic material. In the case of a paracentric inversion loop, where the inverted region does not include the centromere, nonviable gametes can result due to the disruption of gene order and potential gene deletions or duplications.
The percentage of nonviable gametes depends on the location and size of the inversion. For example, let's say that in a population, 10% of individuals carry a paracentric inversion on chromosome 1. During meiosis, crossing over may occur within the inverted region, resulting in an inversion loop.
If the inversion disrupts essential genes or causes large-scale deletions or duplications, the resulting gametes may not be viable. The actual percentage of nonviable gametes resulting from a paracentric inversion loop would vary based on specific genetic factors.
Therefore, the precise percentage cannot be determined without additional information about the inversion and its effects on gene function.