Meiosis

• The first stage of meiosis is called prophase I, where homologous chromosomes pair up and exchange genetic material through crossing over.
• Metaphase I occurs when the paired chromosomes line up along the equatorial plate of the cell.
• Meiosis is the process by which gametes are produced.
• Telophase I marks the end of the first division, with two haploid cells formed that contain half the number of chromosomes as the original parent cell.
• Anaphase I involves the separation of tetrads from one another and their movement to opposite poles of the cell.
• In humans, there are two types of cells - somatic (body) cells and germline (reproductive) cells.
• Anaphase II involves the separation of sister chromatids
• Cytokinesis after Telophase II divides the cytoplasm to produce four haploid daughter cells.
• Cytokinesis after telophase I divides the cytoplasm to produce 2 haploid daughter cells
• Meiosis is important because it produces genetically diverse gametes through crossing over during prophase I, resulting in genetic variation within offspring.
• During meiosis, homologous pairs of chromosomes line up at the equatorial plate and exchange segments of DNA by crossing over.
• The process of meiosis ensures that only one copy of each gene is passed on to each gamete, reducing the risk of homozygous lethal mutations.
• The process of crossing over results in recombinant chromosomes with new combinations of genes.
• Crossing over occurs when non-identical alleles from different parents combine on one chromosome.
• In Prophase II, Centrioles start to separate and the spindle fibers form
• Metaphase II - Chromatids are aligned along the metaphase plate RANDOMLY
• Chromosomes are DNA containing structure that carry genetic info
• Chromosomes are made up of supercoiled DNA wrapped around proteins called Histone
• Haploid: (of a cell or nucleus) having a single set of chromosomes.
• Gametes: Cells used in sexual reproduction
• Diploid: (of a cell or nucleus) containing two complete sets of homologous chromosomes
• Somatic: Cells that are NOT used in sexual reproduction
• Homologous Chromosomes: Chromosomes pairs inherited from each parent, similar but not identical
• Homologous chromosomes


  Chromosomes that are similar in structure and contain the same genes but may have different alleles
• Haploid


  Having a single set of chromosomes
• Identifying cells that are haploid and diploid


  Examine the number of chromosome sets present
• Determining haploid and diploid numbers of chromosomes


  Count the number of chromosomes present
• Autosomes


  Chromosomes that are not sex chromosomes
• Sex chromosomes


  Chromosomes that determine an organism's biological sex
• Humans have 46 chromosomes
• Meiosis


  The process of cell division that reduces the number of chromosomes in a cell by half
• The final result of meiosis is haploid cells
• Meiosis as a reduction division


  The number of chromosomes is reduced by half
• Cells that undergo meiosis

  • Gametes (sperm and egg cells)
  • Sex cells
• Events that increase genetic variation

  • Crossing over
  • Independent assortment
  • Random fertilization
• Similarities and differences between mitosis and meiosis

  Both involve cell division, but meiosis reduces the chromosome number by half while mitosis maintains the chromosome number
• Karyotype


  A visual display of an individual's chromosomes arranged in homologous pairs
• Identifying chromosomal abnormalities in a karyotype


  Examine the number, size, shape, and banding pattern of the chromosomes
• Causes of chromosomal abnormalities

  • Errors during cell division
  • Exposure to radiation or chemicals
• Monosomy


  Having only one copy of a chromosome instead of the usual two