Meiosis and sexual reproduction

• Genes


  Regions on DNA that code for the formation of proteins
• Chromosomes


  • Hundreds of genes, each playing a crucial role in determining the characteristics and functions of the cell
• Human body cells have 46 chromosomes
• Homologous chromosomes


  Chromosomes that have the same length and centromere position as well as sequence of genes that control the same traits

  
• One chromosome comes from the mother, the other from the father
• Gametes


  Sex cells (sperm and egg) that have half the number of chromosomes
• Haploid cell


  Cell with half the number of chromosomes
• Diploid cell


  Cell with the full number of chromosomes (2n)
• Fertilization


  One haploid gamete combines with another haploid gamete to form a diploid cell
• Chromosome types in human body cells


  • Autosomes (first 22 pairs)
  • Sex chromosomes (23rd pair)
• Sex chromosomes


  Determine an individual's gender (X and Y)
• Individuals with XX chromosomes are female, individuals with XY chromosomes are male
• Meiosis


  Reduction division that reduces the number of chromosomes
• Meiosis


  1. Interphase

  2. Prophase I

  3. Metaphase I

  4. Anaphase I

  5. Telophase I

  6. Prophase II

  7. Metaphase II

  8. Anaphase II

  9. Telophase II

  
• Interphase


  Chromatin replicates and condenses into chromosomes

  
• Prophase I


  1. Homologous chromosomes pair

  2. Crossing over between homologous chromosomes

  3. Nuclear membrane breaks down

  4. Spindles form

  
• Crossing over


  Exchange of genetic information between homologous chromosomes, providing variation and genetic diversity

  
• Metaphase I


  1. Spindle fibers attach to centromeres of chromosomes

  2. Homologous chromosomes line up at cell center

  
• Anaphase I


  Homologous chromosomes separated and moved to opposite sides of cell

  
• Telophase I


  1. Spindle fibers break down

  2. Chromosomes relax back into chromatin

  3. Cell divides into 2 cells with 46 chromosomes each
• Prophase II


  1. Chromatin condenses into chromosomes

  2. Spindles form

  
• Metaphase II


  Spindle fibers attach to centromeres of sister chromatids
• Anaphase II


  Spindle fibers shorten and split apart sister chromatids to opposite sides of cell
• Telophase II


  1. Four nuclear membranes appear

  2. Spindles break down

  3. Chromatids relax back into chromatin

  4. Cells divide into 4 cells each with 23 chromosomes
• Surface area

  How much space the outside of an object covers
• Volume

  The amount of space or matter inside the object
• Meiosis involves two rounds of nuclear division with no DNA replication between them.