Learning Objective

In this lesson we will learn about the two types of cell division – involving either mitosis or meiosis – and the process of DNA replication which takes place prior to both.

Learning Outcomes

By the end of this lesson you will be able to:

  • Explain why cell division takes place.

  • Describe the process of DNA replication and explain why it takes place prior to cell division.

  • Describe the process of mitosis, where it occurs and the types of cells it produces.

  • Describe the process of meiosis, where it occurs and the types of cells it produces.

  • Compare and contrast the processes of mitosis and meiosis.

 

 cell division dna replication mitosis meiosis worksheet  year 10 biology pdf workbook

Click images to preview the worksheet for this lesson and the Year 10 Biology Workbook.

 

Cell Division

  • Cell division is the process whereby parent cells divide, resulting in daughter cells.
    Cell division occurs for two main reasons in living things – for growth and for reproduction.
  • Cell division for growth involves the replication of body cells (somatic cells).
    It includes the process of mitosis.
  • Cell division for reproduction involves the production of gametes (sex cells).
    It includes the process of meiosis.
  • Mitosis and meiosis specifically relate the to division of cell nuclei, but they are both immediately followed by division of the whole cell, which is called cytokinesis.

 
cell division 3d

Cell division produces two daughter cells from a parent cell.

(Image: Kateryna_Kon, Adobe Stock)

 

DNA Replication

  • Before a cell divides, it duplicates its genetic material; that is, it makes copies of its DNA and therefore its chromosomes.
    This process is called DNA replication.
  • During DNA replication, the double helix unwinds and the two strands of DNA separate.
    These two strands form templates for new strands of DNA, which are synthesised according to the base-pairing rules.

 
dna replication process

DNA replication produces two daughter DNA molecules from a parent DNA molecule.

(Image: designua, Adobe Stock)

 

  • Once DNA replication is complete, the two daughter molecules of DNA are still part of the same chromosome, but exist as separate arms, called sister chromatids, which are joined at the centromere.

 
chromosome duplication sister chromatids

Following DNA replication, duplicated chromosomes are still attached at the centromere.

 

Mitosis

  • Mitosis involves one round of division, which can be broken down into several stages.
    1. Chromosomes line up along the ‘equator’ of the cell, with sister chromatids on opposite sides.
    2.  
      mitosis lining up of chromosomes metaphase

       

    3. Sister chromatids separate into individual chromosomes and migrate to opposite ‘poles’ of the cell.
    4.  
      mitosis separation of chromatids anaphase

       

    5. The nuclear membrane separates the two sets of chromosomes into two nuclei.
    6.  
      mitosis formation of two nuclei telophase

 

  • Following mitosis, the cells divides in two.
  • Mitosis results in two diploid cells from one diploid cell.
  • The daughter cells produced by mitosis are genetically identical to the parent cells.

 
cell division mitosis

 

Meiosis

  • Meiosis involves two rounds of division, each of which can be broken down into several stages.

 

Meiosis I

  • Meiosis I involves the halving of the number of chromosomes in each cell.
    1. Homologous chromosomes exchange sections of DNA in a process called crossing over or recombination.
    2.  
      meiosis i crossing over of chromosomes prophase

       

    3. Chromosomes line up along the ‘equator’ of the cell, with homologous pairs on opposite sides.
    4.  
      meiosis i lining up of chromosomes metaphase

       

    5. Homologous chromosomes migrate to opposite ‘poles’ of the cell.
    6.  
      meiosis i migration of chromosomes anaphase

       

    7. The nuclear membrane separates the two sets of chromosomes into two nuclei.
    8.  
      meiosis i formation of two nuclei telophase

 

  • Following meiosis I, the cells divides in two.

 

Meiosis II

  • Meiosis II follows a similar process to mitosis.
    1. Chromosomes line up along the ‘equator’ of the cell, with sister chromatids on opposite sides.
    2.  
      meiosis ii lining up of chromosomes metaphase

       

    3. Sister chromatids separate into individual chromosomes and migrate to opposite ‘poles’ of the cell.
    4.  
      meiosis ii separation of chromatids anaphase

       

    5. The nuclear membrane separates the two sets of chromosomes into two nuclei.
    6.  
      meiosis ii formation of four nuclei telophase

 

  • Following meiosis II, the cells divides in two.
  • Meiosis I results in two haploid cells from one diploid cell.
    Meiosis II results in four haploid cells from two haploid cells.
    Overall, meiosis results in four haploid cells from one diploid cell.
  • The daughter cells produced by mitosis are genetically unique.

 
cell division meiosis

 

Summary

  • Cell division (cytokinesis) produces two daughter cells from a parent cell.
  • Cell division for growth involves mitosis and the replication of body cells (somatic cells).
    Cell division for reproduction involves meiosis and the production of gametes (sex cells).
  • DNA replication produces two daughter DNA molecules from a parent DNA molecule.
    Duplicated chromosomes consist of sister chromatids joined at the centromere.
    DNA replication takes place before mitosis and meiosis.
  • Mitosis involves one round of division, resulting in two diploid cells that are genetically identical to the parent cells.
    Meiosis involves crossing over and two rounds of division, resulting in four haploid cells that are genetically unique.

 
comparing mitosis and meiosis

 

(Header image: Sebastian Kaulitzki, Adobe Stock)

 

 cell division dna replication mitosis meiosis worksheet  year 10 biology pdf workbook

Click images to preview the worksheet for this lesson and the Year 10 Biology Workbook.