Describe the two ways in which meiosis produces new combinations of genes.

Random assortment of maternal and paternal chromosomes during cell division is the first way that meiosis produces new combinations of genes. In each pair of chromosomes, one copy was inherited from each parent. Random combinations of parental chromosomes arise in metaphase I when the maternal and paternal members of each pair line up at random with respect to all the other pairs. In other words, the arrangement of any chromosomal pair can be maternal:paternal or paternal:maternal. As a result, cells produced in meiosis I are much more likely to receive a combination of maternal and paternal chromosomes than they are to receive a complete set of maternal chromosomes or a complete set of paternal chromosomes.

Crossing over is the second way meiosis generates new combinations of genes. This process involves the physical exchange of parts between non-sister chromatids. Members of a chromosome pair carry identical genes but may carry different versions of those genes (alleles). For example, a chromosome may carry a gene for eye color. One copy of the chromosome may carry an allele for blue eyes, while the other carries an allele for brown eyes. The exchange of chromosome parts during crossing over creates new combinations of alleles inherited from each parent.