IMAT 2021 Q24 [Structure Formed by Mitosis]

Which one of the diagrams (not drawn to scale) represents a structure that is formed by mitosis ?

The correct answer is A : the immune cell.

What is mitosis ?

It is a type of cell division that begins with the duplication of the DNA.

Furthermore, the daughter cells are genetically similar to the mother cell : a gene A with the allele y is transmitted to the daughter cells.

Its purpose is to ensure cell multiplication for tissue repair or growth.

In other words, from a single diploid mother cell (2n), 2 diploid daughter cells (2n) are obtained.

A diploid cell has 2 complete sets of chromosomes, usually written as being a 2n cell, as opposed to a haploid cell, that only has 1 set of each chromosome, and written as a n cell.

In which cells does mitosis occur ?

It only occurs in eukaryotic cells : as opposed to prokaryotic cells, their genome is stored inside a nucleus. There are also only 3 types of eukaryotic cells that undergo mitosis :

  1. somatic cells which are what we call any cells that aren’t sperm or egg cells
  2. adult stem cells
  3. cells in the embryo

Therefore, it is important to be able to recognize the different structures :

  1. A looks like it is an immune cell (a neutrophil) : it si a somatic cell and therefore undergoes mitosis

  2. B looks like a bacteria : it is neither for these types of cells. Bacteria reproduced by binary fission and not mitosis.

  3. C looks like a mitochondrion : it is an organelle and not a cell. They divide by mitochondrial fission and not mitosis.

  4. D looks like a chloroplast : it is an organelle and not a cell. Similarly to the mitochondrion, they divide by fission and not mitosis.

  5. E looks like a virus : they do not undergo mitosis. Instead, they replicate through a 6 step process :

    • attachment to the host cell
    • penetration of the host cell by endocytosis
    • uncoating of the external proteins to release the genomic nucleic acid
    • gene expression and replication
    • assembly of the new virions
    • release
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