Meiosis U.2 L.3

  • asexual reproduction leads to genetically identical daughter cells

  • sexual reproduction results in offspring that is genetically different from both parents

  • gametes are specialized sex cells for reproduction (sperm/eggs)

  • gametes are produced by reproductive organs called gonads (testes and ovaries)

  • fertilization is when two parents combine and create a new cell called a zygote

  • Chromosomes are arranged into 23 pairs, called homologous chromosomes

  • the human body (somatic cells) are called “diploid” (2n=46), meaning they contain 46 chromosomes

  • gametes are called “haploid” they only contain 23 chromosomes in total (n=23)

  • men have X&Y karyotypes, and women have X&X karyotypes

  • Meiosis is a cell division that creates sex cells

  • meiosis has 2 outcomes : genetic reduction (less genetic info) and genetic recombination (crossover of chromosome makeup)

  • Meiosis has 2 division rounds with the first one containing DNA replication

  • 8 stages in division during Meiosis

  • Synapsis : the pairing of homologous chromosomes

  • crossing over : parts of the chromosomes can be exchanged, important for genetic diversity (half chromosome is blue, half red)

  • Prophase l : each chromosome gets duplicated in interphase

  • Metaphase l : the pair of chromosomes line up alone the equator, spindle fibers attach to the centromere of each homologous chromosomes, Independent assortment leads to different combinations of chromosomes in each gamete

  • Anaphase l : Homogolonous pairs seperate and move to opposite poles (sister chromatids stay together), one single chromosome (made up of 2 sister chromatids) goes to each side, changed from diploid to haploid (different from Mitosis since chromatids stay together)

  • Telophase l : homologous chromosomes uncoil, cytokinesis takes place 2 haploid cells are formed containing 23 chromosomes

  • Prophase ll : DNA doesnt duplicate (already did), spindle fibers form

  • Metaphase ll : haploid number of chromosomes align at the equator

  • Anaphase ll : the centromere breaks apart and sister chromatids are pulled to each side

  • Telophase ll : cell division is complete, four haploid daughter cells are produced

  • differences between Mitosis and Meiosis : Meiosis created 4 cells, Mitosis creates 2, Mitosis is indentical, Meiosis is non-identical, Mitosis is somatic, Meiosis is reproductive

  • Spermatogenesis : the process of sperm production is the testes, go through meiosis in puberty

  • process begins with a diploid (2n) cell called a spermatogonium

  • spermatogonia reproduces by mitosis, and the resulting cells go through meiosis to create 4 haploid cells

  • sperm contain flagellum for movement to the egg cell

  • oogenesis is the egg production in the ovaries

  • oogenesis starts with a diploid cell called an oogonium

  • the oogonia reproduce by mitosis but stop at prophase l, if not fertilized

  • when you get your period, oogonia contrinue through meiosis

  • at the end of telophase l, we stuff as much cytoplasm as possible into one of the egg cells and discard it

  • Meiosis ll creates a ovum and polar body, polar bodies are recycled as waste due to the cytoplasm