Chapter 2 Biology - Reproduction

• autosomal cells


  diploid (2n)

  2 copies of each chromosome
• diploid


  2 sets of chromosomes

  
• haploid


  having a single set of unpaired chromosomes

  
• how many chromosomes do humans have?

  46 (23 pairs)
• Cell Cycle


  series of events that cells go through as they grow and divide

  
• Interphase


  first three stages of cell cycle, G1, S and G2 and cells are condensed into chromatin
• G_0 stage


  cells that do not divide and carry out its functions
• G_1 stage: presynthetic gap


  cells increase in size and create organelles for energy and protein production
• S stage (synthesis of DNA)

  the cell replicates its genetic material so that each daughter cell will have identical copies
• G_2 (post synthetic gap)

  the cell passes through another quality control checkpoint to make sure DNA replication proceeded correctly
• M stage: Mitosis


  •Mitosis (2 identical cells created from a single cell) + cytokinesis (splitting of cytoplasm and organelles into 2 daughter cells)

  •Occurs in somatic cells (cells not involved in sexual reproduction)

  •Mitosis consists of 4 phases

  
• Somatic cells


  Any cells in the body other than reproductive cells
• p53 role


  tumor suppressor that is used at the G1/S/G2/M checkpoints
• cyclins


  proteins that regulate the cell cycle
• cyclin dependent kinase


  enzyme to which cyclin binds during interphase and mitosis, triggering and controlling activities during the cell cycle
• Prophase


  Chromosomes become visable, nuclear envelop dissolves, spindle forms
• Metaphase


  Chromosomes line up in the middle of the cell
• Anaphase


  chromosomes separate and move to opposite ends of the cell
• Telophase


  spindle fibers disassemble and the chromosomes return to a less tightly coiled chromatin state
• Cytokinesis


  division of the cytoplasm
• centrosome


  A structure in animal cells containing centrioles from which the spindle fibers develop.
• centrioles


  Located near the nucleus and help to organize cell division
• spindle fibers


  help pull apart the cell during replication and are made up of micrtubules
• kinetochores


  The structures on sister chromatids where microtubules attach

  
• Main difference between meiosis and mitosis

  Mitosis makes genetically identical copies and meiosis makes new copies of DNA derived from parents
• Gametocytes


  cells that divide to form gametes
• Gametes


  sex cells
• Meiosis I


  Homologous chromosomes separate
• Meiosis II


  Sister chromatids seperate
• Reductional Division


  An alternative name for meiosis I, since this division reduces the number of chromosomes by half.
• Equational division


  Another name for meiosis II because cells in meiosis II have the same number of chromosomes at the beginning and at the end of the process.
• Prophase I


  The chromosomes condense, and the nuclear envelope breaks down. crossing-over occurs.
• Synapsis


  Pairing of homologous chromosomes
• Crossing Over


  Process in which homologous chromosomes exchange portions of their chromatids during meiosis.
• Recombination


  A combining of genes or characters different from what they were in the parents
• Linkage


  a phenomenon in which alleles that are located in close proximity to each other on the same chromosome are more likely to be inherited together
• Metaphase I


  homologous pairsline up at the plate
• Anaphase I


  homologous pairsseparate and move towards opposite pole of cell
• What happens during disjunction?

  Each chromosome of paternal origin separates from the homologue of maternal origin.
• What is the outcome of disjunction?

  Either chromosome can end up in either daughter cell, leading to random distribution of homologous chromosomes.