meiosis - aka "reduction division"

• makes haploid daughter nuclei
• diploid - chromosomes coming in pairs (normal in eukaryotic nuclei)
• homologous chromosomes - chromosomes in a pair
  • loci - sites for a gene, same in both homologous chromosomes
• haploid - only 1 chromosome in each pair found (normal in gametes)
• 2 rounds of chromosomal separation, 1 round of DNA replication
• synapsis - pairing of homologous chromosomes
  • alleles - homologous segments of genetic material, gets exchanged when chromosomes paired up
  • crossing-over - creates new genetic combination
  • no gain/loss of genetic material
• meiosis I - homologous chromosomes split
• meiosis II - chromatids split

gametogenesis - formation of gametes

• gamete - reproductive cells w/ haploid nuclei
• spermatogenesis - formation of sperm
  • occurs in testes (made of seminiferous tubules)
  • spermatogonia - diploid cells in tubules that constantly divide mitotically
  • primary spermatocytes - cells that move toward lumen and start meiosis
  • secondary spermatocytes - produced by meiosis I of primary spermatocyte, has haploid set of double-stranded chromosomes
  • spermatids - produced by meiosis II of secondary spermatocytes, matures into sperm cells
• oogenesis - formation of egg
  • occurs in ovaries of females
  • oocyte - cells in ovary that produces female gametes
  • eggs not produced continually, only during early fetal development
  • primary oocytes - about 2 million initially created, start meiosis I but stop in prophase I
  • follicular cells - surround oocytes to form follicules
  • hormones stimulate growth of 1 or 2 follicles per month after puberty
  • ovulation - release of oocyte from ovary, after oocyte completes meiosis I to produce secondary oocyte and polar body (eventually disintegrates)
  • Graafian follicle - mature follicle containing secondary oocyte
  • meiosis II (only after sperm penetrates egg) creates polar body and haploid egg cell ready for fertilization (nuclei fusion)
  • corpus luteum - formed by remaining follicle cells, prepares the uterus for fertilized egg w/ hormones

plant gametogenesis - plants have alternation of generations between haploid/diploid  

• meiosis occurs in anthers/ovary of flowers
• anther creates spores (pollen) that eventually produce male gametes
• ovary creates spores (ovule) that eventually produce female gametes