The closer together two genes are on a chromosome, the less likely their alleles will be separated by crossing-over.

Yes, that's correct. The process of crossing-over occurs during meiosis, where homologous chromosomes exchange genetic material. This process can lead to genetic recombination, where alleles for different genes can be shuffled. However, if two genes are very close together on the same chromosome, they are less likely to be separated by crossing-over. This is because the chance of a crossover event occurring between them is lower than if they were further apart. This phenomenon is known as genetic linkage.