Final answer:
Arabidopsis thaliana is expected to have high levels of linkage disequilibrium due to its small genome, potentially leading to lower recombination rates. Magnus Nordborg is known for his work on Arabidopsis genetics, but specific discoveries are not provided in the material. Linkage disequilibrium is more common in certain population dynamics and early geneticists like Mendel seemed to have avoided it in their foundational genetics work.
Step-by-step explanation:
The expectation that Arabidopsis thaliana would display high levels of linkage disequilibrium might stem from its relatively small genome, which could result in lower recombination rates overall. However, detailed genomic studies, such as those by the Arabidopsis Genome Initiative, have provided insights into its genetic variation and structure.
Regarding Magnus Nordborg's contributions, while he is a renowned geneticist known for his work on Arabidopsis thaliana, the provided material does not specify a particular discovery, thus we cannot confidently articulate what Magnus Nordborg discovered without further information.
Linkage disequilibrium is often observed in species that have undergone recent population bottlenecks, self-fertilization, or have small population sizes, factors which lead to less genetic shuffling and recombination. On the other hand, history shows that early geneticists like Mendel were fortunate or selective in their studies of pea plants to avoid encountering linkage, which would have complicated the observation of independent assortment.
Mendel focused on traits controlled by genes that were either on separate chromosomes or sufficiently far apart on the same chromosome, thereby observing independent assortment consistently.