Mitosis & the Cell Cycle (OCR Gateway GCSE Biology: Combined Science)

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The Cell Cycle

  • The cell cycle can be thought of as the life cycle of a cell
  • It is the series of growth and development steps a cell undergoes
    • From its formation to the point it divides to make new cells
  • The cells in your body need to be able to divide to help your body grow and repair itself
    • Cells grow and divide over and over again
    • For this to happen the DNA has to be copied
  • All body cells (except gametes) are produced by mitosis which happens as part of the cell cycle

There are 3 parts of the cell cycle

  • Interphase - consists of phases of cell growth and synthesis of new DNA
    • Just before mitosis, the DNA in the nucleus copies itself exactly (forming duplicate chromosomes)
  • Mitosis - Chromosomes line up along the centre of the cell and are pulled apart
  • Cytokinesis - The cell cytoplasm and membrane divides to produce two daughter cells
    • Each new cell has a copy of each of the chromosomes

The 3 stages of the cell cycle, downloadable IGCSE & GCSE Biology revision notes

The three stages of the cell cycle

Mitosis

  • The process of mitosis is itself made up of a series of stages that begin after interphase has occurred
    • DNA was copied during interphase to produce duplicate chromosomes 
  • During mitosis, the sets of duplicated chromosomes line-up in the centre of the cell
  • Cell fibres attach to the duplicated chromosomes and pull them apart
  • One chromosome arm (chromatid) from each set is pulled to each end of the cell
  • A new nucleus forms around each group of chromosomes
  • After this, the cytoplasm and cell membranes divide in a process known as cytokinesis. This results in the formation of two genetically identical daughter cells

Mitosis, IGCSE & GCSE Biology revision notes

Diagram showing the process of cell division by mitosis

Exam Tip

You do need to appreciate the three overall stages of the cell cycle:

  • Growth phase (including chromosome doubling)
  • Mitosis
  • Cytokinesis (division of cytoplasm and the cell membrane)

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Phil

Author: Phil

Phil has a BSc in Biochemistry from the University of Birmingham, followed by an MBA from Manchester Business School. He has 15 years of teaching and tutoring experience, teaching Biology in schools before becoming director of a growing tuition agency. He has also examined Biology for one of the leading UK exam boards. Phil has a particular passion for empowering students to overcome their fear of numbers in a scientific context.

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