Mitosis & Meiosis 5.2

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Inquiry Question 2: How important is it for genetic material to be replicated exactly?

Content Descriptor: Model the processes involved in cell replication, including, but not limited to:

Mitosis and Meiosis: (5.2.1)


Interphase – The normal function of the cell. In this phase, the single strand chromosomes divide into double stranded chromosomes. Membrane begins to disintegrate.

Prophase – Chromosomes condense, becoming visible in their double stranded form.

Metaphase – Middle phase, double stranded chromosomes line up in the centre of the cell, attached to miotic spindles.

Anaphase – Centromeres divide, pulling the chromatids apart into single strands. Telophase – Two nuclei form.

Cytokinesis – Fluid (cytoplasm) divides.


Meiosis and mitosis:


DNA replication using the Watson and Crick DNA model, including nucleotide composition, pairing and bonding: (5.2.2)

History of Watson and Crick:

In the 1940’s it was hypothesized that heredity was caused by and carried on proteins. This was contradicted however by Watson and Crick in 1953 through some unethically liberated help from Rosalind Franklin, who discovered that DNA formed a double helix structure, and the coding was performed by 4 nitrogenous bases.


Stages of DNA replication:

  1. Initiation – Helicase enzyme unwinds the double helix. Cell also creates a short sequence ofRNA primers
  2. Elongation – Polymerase enzyme controls elongation, occurring in a 5’è3’ direction adding complementary nucleic 
  3. Termination– Ligase enzyme snips off a section of telomere at the end of 


Assess the effect of cell replication processes on the continuity of species: (5.2.3)


Mitosis ensures the continuity of the species through allowing organism growth and repair. This allows an organism to grow and survive to sexual maturity to continue the genes of the species. It is important that this DNA is replicated exactly to ensure the daughter cells perform the same function as the parent.


Ensures continuity through providing genetic variation for the resultant daughter cells. This genetic variation provides the different combination of genetic information (alleles) upon which the mechanism of natural selection acts. Thus, meiosis ensures that organisms are genetically varied, ensuring that the species can adapt to changes in the environment.

Inquiry Question Review: How does reproduction ensure the continuity of a species? (5.2.4)

You should be able to:

  • Describethe Watson and Crick genetic model and DNA 
  • Describemeiosis and 
  • Assesswhy the processes above are important for the survival of a