AP Bio Study Guide

Big Idea 3.A

How is meiosis different from mitosis?

While mitosis clones diploid cells for the purposes of growth, repair, and asexual reproduction, meiosis creates haploid cells for the production of gametes (sex cells). Each gamete is unique, due to crossing over (parts of homologous chromosomes switching), independent assortment (chromosomes have two possible orientations when they line up in the middle during metaphase) and random fertilization (a random gamete is actually fertilized in the end).

Meiosis has two rounds of division, but only duplicates its DNA before the first. This creates haploid cells (half the number of chromosome), which are combined with another haploid cell during fertilization to create a diploid cell with the normal number of chromosomes.