Cellular Division

• Meiosis: A type of cell division that produces four haploid daughter cells from one diploid parent cell
• Homologous chromosomes: Chromosomes that are identical in length and structure, one from mother and one from father
• Meiosis 1: homologous chromosomes move to opposite poles, diploid cells separate into haploid cells.
• Meiosis 2: separation of two chromatids
• Prophase 1:

  • nuclear membrane disappears, centrioles split, spindle fibers appear
  • chromosomes come together to form a homologous pair
  • tetrads come close together during synapsis
  • crossing over may occur
• Tetrads: 4 cells that are identical to each other and are produced by meiosis
• Synapsis: The joining of homologous chromosomes during meiosis
• Crossing over: The exchange of genetic material between homologous chromosomes during meiosis
• Metaphase 1: Chromosomes line up along the equator of the cell in two rows
• Anaphase 1: the whole chromosome moves to opposite poles

  • diploid mother cell becomes two haploid daughter cells
  • centromeres do not break
• Telophase 1: cytoplasm divides forming two cells (not identical)
• Prophase 2: nuclear membrane dissolves, spindles form
• Metaphase 2: Chromosomes line up along the equator of the cell, in one row
• Anaphase 2: Sister chromatids separate and move to opposite poles of the cell
• Telophase 2: nuclear membrane reforms, second division of cytoplasm takes place, 4 daughter cells are formed

  • marks the end of meiosis (does not continue)
  • all 4 cells have variation
• Segregation: the whole chromosome moves to one pole or the other
• Spermatogenesis: production of sperm (quantity)
• Oogenesis: egg formation (quality)
• Non-disjunction: The failure of a pair of homologous chromosomes to separate properly during meiosis
• Trisomy: a condition in which an extra copy of a chromosome is present in the cell nuclei, causing developmental abnormalities.
• Monosomy: the condition of having a diploid chromosome complement in which one chromosome lacks its homologous partner.
• Karyotype: the number and visual appearance of the chromosomes in the cell nuclei of an organism or species.
• Amniocentesis: A procedure that involves inserting a needle into the amniotic fluid to obtain a sample of the fetus's cells.
• CVS: edge of placenta, removal of a small sample of the placenta