6: cell division, diversity, differentiation

• cytokinesis

  cytoplasmic division following nuclear division, resulting in 2 daughter cells
• interphase


  phase of a cell cycle where the cell is not dividing
• mitosis


  type of nuclear division that produces daughter cells genetically identical to eachother and to their parent cell
• mitosis prophase

  1. identical sister chromatoids shorten and thicken as the DNA supercoils
  2. Nuclear envelope breaks down
  3. Centriole divides and thedaughetr centrioles move to opposite end of the cell
  4. spindle forms (made out of tubulin and part of the cytoskeleton)
• Mitosis METAPHASE

  1. the pair of chromatids attach to spindle threads at the equator region
  2. attach by centromeres
• Mitosis ANAPHASE

  1. centromere of each pair of chromatids splits
  2. motor proteins pull sister chromatids in opposite directions
  3. cuz centromeres goes first the chromatids (now chromosomes) become a V shape
• Mitosis TELOPHASE

  1. separated chromosomes reach poles
  2. new nuclear envelope forms around each set of chromosomes
  3. cell contains 2 nuclei genetically identical to each other and parent cell
• significance of mitosis in the life cycle

  1. asexual reproduction
  2. growth
  3. tissue repair
• haploid


  having only one set of chromosomes... represented by the symbol 'n'
• homologous chromosomes


  matching chromosomes containing same genes at the same places (loci) May contain different alleles for some of the genes
• meiosis


  type of nuclear division that results in the formation of cells containing half the number of chromosomes of the parent cell
• stages of mitosis

  1. prophase
  2. metaphase
  3. anaphase
  4. telophase
• stages of meiosis

  1. prophase 1
  2. metaphase 1
  3. anaphase 1
  4. telophase 1
  5. prophase 2
  6. metaphase 2
  7. anaphase 2
  8. telophase 2
• Meiosis PROPHASE 1

  1. chromatin condenses and each chromosome supercoils
  2. nuclear envelope breaks down
  3. spindle threads form
  4. chromosomes come together in their homologous pairs
  5. each member of the pair consists of 2 chromatids
  6. crossing over occurs where non-sister chromatoids wrap around eachother and maybe swap sections so that alleles are shuffled
• Meiosis METAPHASE 1

  1. the pairs of homologous chromosomes still in their crossed over state attach along the middle
  2. each chromosome attached to a spindle thread by its centromere
  3. independent assortment: homologous pairs are arranged randomly and facing opposite poles
  4. the way that they line up in metaphase determines how they will segregate independently when pulled apart during anaphase
• Meiosis ANAPHASE 1

  1. homologous chromosomes are pulled apart by motor protein which drag them along tubulin threads
  2. centromeres don't divide and each chromosome consists of two chromatids
  3. crossed over areas are separated resulting in swapped areas of chromosomes and allele shuffling
• Epithelial

  Lining tissue
• Connective tissue

  Hold structures together and provide support eg. Blood, bone, cartilage
• Muscle tissue

  Made of cells that are specialised to contract and care movement
• Nervous tissue

  Made of cells specialised to conduct electrical impulses
• Meiosis TELOPHASE 1

  1. nuclear envelope forms around each group of chromosomes
  2. cytokenisis occurs and 2 haploid daughter cells are produced
• Meiosis ANAPHASE 2

  1. pair of sister chromatoids are are separated...
  2. each new daughter cell inherits one chromatid from each chromosome...
  3. 4 genetically diff haploid daughter cells are produced= gametes
• Structural adaptation include

  • Shape of the cell
  • Organelles found in cell
• Erythrocyte


  Red blood cell
• Function of erythrocyte

  Transport oxygen around the body and to the lungs and carbon dioxide out
• Neutrophil function

  Destroy pathogens by phagocytosis and the secretion of enzymes
• Root hair cell function

  Absorption of water and mineral ions from soil
• Spermatoza function

  To fuse with an egg and initiate development of embryo
• Cilliated epithelium function

  Moving substances across surface of a tissue
• Squamous epithelium function

  Provides a surface covering or an outer layer found on a variety of organs and structures
• Palisade cell function

  Carry out photosynthesis to produce glucose and carbon dioxis
• Guard cell function

  Control the opening and closing of the stomata to regulate water loss and gas exchange
• Mitosis

  Nuclear division
• Cytokinesis

  cytoplasmic division
• G1 Checkpoint

  Cell checks that all chemicals needed for replication us present. Also looks for dmg in the DNA
• G2 checkpoint

  The cell checks that all DNA has been replicated without damage it can then go into mitosis