We didn’t go into this in the book, because the processes are complicated enough as they are. During the replication process of meiosis I, the homologous chromosomes actually exchange genes. That way, when they are duplicated, they are not identical to the originals. That adds a lot of variability to the genes. After all, If I could only give two different chromosomes and my spouse could only give two different chromosomes, I could only have 4 genetically different children. Because of the gene exchange that occurs during the duplication in meiosis I, I am not giving copies of EITHER of my chromosomes. I am donating a mixture of BOTH of my chromosomes.