Mitosis + Meiosis

• Somatic cells are body cells with 2N amount of chromosomes
• Gametes are sex cells (eggs/sperm) produced through meiosis with 1N chromosomes
• Homologous chromosomes are chromosomes that are very similar to each other, carrying the same type of genetic information that contain the same genes
• diploid cells have 2 copies of each chromosome
• haploid cells only have 1 copy of each chromosome
• fertilization is the uniting of a sperm and an egg resulting in a diploid zygote (fertilized egg)
• gametes of offspring do not have the same traits as teh parents due to crossing over and independent assortment (prophase + metaphase I)
• during prophase I, each pair of chromosomes lines up next to its homologue, producing tetrads
• a tetrad consists of four chromatids, where portions of the chromatids twist around each other and break off, attaching to the adjacent chromosomes (crossing over)
• crossing over is the exchange of genetic information between segments of homologous chromosomes, and the offspring receives a new genetic information combination
• independent assortment: homologous pairs line up opposite of each other at the equator (random paternal + maternal locations) and they are separated
• variation leads to offspring to be able to survive, be better suited to their environment, and pass more variations to their offspring
• crossing over leads to evolution
• gametogenesis: meiosis produces 4 haploid cells that are different;

  • in males, meiosis results in four sperm cells
  • in females, four cells are produced but only one will become a functional egg, whilst the other 3 become Polar bodies.
  • all of the cytoplasm and organelles are put into the egg cell
• Oogenesis: polar bodies form because eggs do not divide equally, resulting in cells with the same DNA but the other 3 are much smaller
• spermatogenesis: produces 4 functioning sperm
• sexual reproduction: gametes fusing to create a zygote
• meiosis: the process that produces gametes
• Nondisjunction: when chromosomes fail to separate evenly (occurs during anaphase)

  • contributes to genetic disorders, determined through karyotyping
• autosomes: chromosomes that carry traits (chromosomes 1-22)
• sex chromosomes - chromosomes with genes related to biological sex (XX - female, XY - male)
• Karyotyping: the image of all 23 pairs of chromosomes, arranged by size (largest to smallest), with sex chromosomes being the last
• Monosomy: the absence of one member of a pair of chromosomes; only one copy of a chromosome instead of the normal 2
• Trisomy: the presence of an extra chromosome, with 3 copies of a chromosome instead of the normal 2 (ex: down syndrome)
• cytokinesis: the division of the cytoplasm
• mitosis: the division of the nucleus
• in mitosis, each daughter cell will get a complete set of chromososmes
• in mitosis, the 2 daughter cells will be identical to the mother cell.
• S (synthesis) phase: the replication of DNA occurs
• G2 phase: prepares the special cell structures necessary for cell division
• Interphase: time between cell divisions and the chromosomes are replicated (90%. of the cell cycle)
• centrioles: organelles that create the spindle fibers used to separate sister chromatids
• prophase: chromosomes condense and become visible, nuclear envelope breaks down (IN MITOSIS)
• Metaphase: the double stranded chromosomes become attached to the spindle fibers and move to the equator of the cell
• Anaphase: centromeres replicate then separate and the spindle fibers begin to shorten, pulling the chromatids apart
• Telophase: nuclear membrane begins to form around the new set of chromosomes (cleavage furrow occurs only in animal cells. plant cells have a cell plate.)
• multicellular organisms: mitosis is used for growth and repair
• unicellular organisms: mitosis results in new offspring
• G0 phase: the non-dividing state of the cell cycle
• uncontrolled cell growth: cells divide uncontrollably and form tumors, causing cancer