cell division

• What's the importance of cell division

  -repair and replacement of old and damaged cells&tissues

  -reproductions

  -growth
• the nucleus has 46 chromosones that carry genes for making new organisms
• strands of DNA make up our chromosones
• genes are sections that has info to control a charactersitic in our body
• SMALL-BIG

  1. gene
  2. DNA
  3. chromosone
  4. nucleus
  5. cell
• Mitosis is needed for growth, replacement of damaged and dead cells and reproduction
• Multicellular organisms need cells to divide so that organisms can grow and repair damaged tissue
• Cell cycle


  The series of stages that a cell goes through as it is growing and dividing
• Cell cycle

  1. Cell growth

  2. DNA replicates

  (interphase)

  3. Mitosis

  (mitotic phase)
• Mitosis


  The stage of the cell cycle when the cell divides
• Before a cell can divide, it must grow and make copies of all the organelles such as mitochondria and ribosomes
• The cell must also replicate the chromosomes in the nucleus, then it can divide by mitosis
• Mitosis

  1. Two complete sets of chromosomes are pulled to opposite sides of the cell

  2. Two new nuclei form

  3. Cell splits into two daughter cells
• The daughter cells are both genetically identical to the parent cell
• Meiosis produces four non-identical haploid gametes (sex cells)
• Cell differentiation is the process where cells change to become specialised to do a certain job
• Meiosis is used for sexual reproduction
• In mitosis the number of chromosomes stays the same but in meiosis it halves
• There are two types of cell division: Mitosis produces two identical diploid daughter cells, Meiosis produces four non-identical haploid gametes (sex cells)
• Meiosis

  Reduction division in a cell in which the chromosome number is halved from diploid to haploid
• Gamete

  Sex cell (sperm in males and ova/eggs in females)
• Meiosis

  1. Copies of the genetic information are made

  2. The cell divides twice to form four gametes, each with a single set of chromosomes

  3. All gametes are genetically different from each other
• During fertilisation, two haploid gametes fuse to form one diploid cell
• Meiosis occurs in the testes of men and ovaries of women
• Mitosis

  • A form of cell division which produces two identical, diploid body cells
• Meiosis


  • A form of cell division which produces four non-identical, haploid sex cells or gametes (sperm and ova in humans)
• Haploid cells


  Contains only 1 set of chromosones
• Diploid


  contains 2 sets of chromosones
• karytope

  shows the full set of chromosones of an individual of arranged in sequence
• mitosis

  before the cell divides, it copies its DNA and form x shaped chromosones

  the chromosones line up across the centre of the cell

  a membrane forms in each half of the nuclei

  the cytoplasm then divides making 2 identical cells (cytokinesis)
• Why is cell specialisation important for the development and growth of a healthy baby from a fertilised egg?


  cells diffenteriate to form different tissues and organs to peform functions
• turner syndrome


  only affects females. results when one of the x chromosones is missing/partially missing
• chromosone abnormalties occur with older cells and cell division
• 90% of a cells life is in interphase
• a cell checkpoint is to check that the cell is growing and replicating DNA correctly before division. if a cell fails a checkpoint, it will self destruct (Apoptosis)
• somantic cell - not a sex cell