• Unit 8: Cellular Reproduction: Meiosis

    Meiosis is a specialized type of cellular reproduction that only occurs in the ovaries and testes and results in an egg or sperm, respectively. Sexual reproduction is responsible for the amazing amount of diversity within a species. When sperm fertilizes an egg, the resulting offspring contain genes from the father and the mother. In essence, you contain genes from ALL of your ancestors, at least in a small part.

    Completing this unit should take you approximately 4 hours.

    • 8.1: Cell Division, Meiosis, and Sexual Reproduction

      Meiosis is a type of cell division that leads to the production of non-identical daughter cells. These sex cells contain half the genetic information and are combined for sexual reproduction. Sexual reproduction is critical for the diversity of living things. 

      The process of meiosis is unique to animals that reproduce sexually. The life cycle of any sexual species features fertilization, which is the fusion of unicellular gametes (one male gamete and one female gamete) to produce a unicellular zygote. The unicellular zygote produced by fertilization carries the chromosomes from both gametes.

      Consequently, the ploidy (the number of sets of chromosomes in a cell) of the zygote is double the ploidy of the gametes. If fertilization were the only process occurring in each generation, then the ploidy would double each generation (tetraploid, then octoploid, etc.), and the zygote would not be able to contain the DNA. To prevent the ploidy from doubling each generation, a separate process is needed to cut the ploidy in half.

    • 8.2: Chromosomes, Chromatids, and Chromatin

      Chromosomes are unique collections of genetic material that make up each of us as individuals. They are made up of chromatin which is composed of histone proteins and DNA. When DNA is copied, chromatids are formed to be passed on to cells upon cell division.

    • Unit 8 Assessment