Cell division 1.6

The control of cell division is just as essential for the survival of multicellular organisms as it is for the reproduction of single celled organisms.  This topic covers the movement of chromosomes in the division of eukaryotic cells by mitosis. There is a section about the control of the cell cycle and how some cells can begin dividing out of control and cause cancer. The differences between primary and secondary tumours are also included.


Key words

Learn and test your biological vocabulary for 1.6 Cell division using these flashards 


Clean sweep - quick revision through the whole topic

These slides summarise the essential understanding and skills in this topic. 
They contain short explanations in text and images - good revision for all students.

Read the slides and look up any words or details you find difficult to understand.

Video tutorial

A short video tutorial is planned here.

Revision summary list for 1.6 Cell division

  • Mitosis is division of the nucleus into two genetically identical daughter nuclei.
  • Chromosomes condense by supercoiling during mitosis.
  • Cytokinesis occurs after mitosis and is different in plant and animal cells.
  • Interphase is a very active phase of the cell cycle with many processes occurring in the nucleus and cytoplasm.(including G1, S, G2)
  • Cyclins are involved in the control of the cell cycle.
  • Mutagens, oncogenes and metastasis are involved in the development of primary and secondary tumours.

Skills

  • Skill: Identification of phases of mitosis in cells viewed with a microscope or in a micrograph.(prophase, metaphase, anaphase and telophase).
  • Skill: Determination of a mitotic index from a micrograph.
  • Application: The correlation between smoking and cases of cancer.

Revision mindmap

These diagram summaries cover the main sections of topic 1.6 Cell division.
Study them and draw your own list or concept map from memory.

Review questions

This self-marking quiz containins questions covering the understandings for this topic.

1

How cells are produced when a diploid cell does one division of mitosis?

Mitosis is division of the nucleus into two genetically identical daughter nuclei in eukaryote cells.
A diploid cell will produce two diploid daughter cells in one division of mitosis.

2

The DNA of eukaryote cells is organised into chromosomes

What happens to the DNA at the beginning of mitosis?

Chromosomes condense by supercoiling during mitosis. This makes the chromosomes visible.

The DNA replicates during interphase, not prophase.

3

The image below was taken in 1825 and shows part of the cell cycle.

What type of cells is this and at which stage of the cell cycle?

Cytokinesis occurs after mitosis in plant and animal cells. The chromosomes are uncoiled.

Plant cells build a new cell wall which divides the cytoplasm.
Animal cells form a cleavage furrow (likes a wasps waist) as they don't have cell walls.

4

During interphase of the cell cycle what happens to the DNA in the nucleus?

Under the microscope there is little change during interphase.
However interphase is a very active phase of the cell cycle with many processes occurring in the nucleus and cytoplasm. (It is subdivided into G1, S, G2)
DNA replication occurs during the S-phase.

5

The diagram below shows the expression of cyclins in the cell cycle.

What is the function of these cyclin proteins in the cell cycle?

Cyclins are involved in the control of the cell cycle. The details of the control points and the names of different cyclin molecules are not required for IB, just an understanding that there are several different cycling, their concentrations change and that this controls the cell cycle.

6

Which two of the factors below are involved in the development of tumors in cancer? (Tick two answers)

Mutagens, oncogenes are involved in the development of primary tumours and
metastasis in the development of secondary tumours.

7

The image below shows two cells undergoing mitosis.

Which of the following correctly identifies the stage of mitosis for each of the cells?

Identification of the phase of mitosis is an important skill.
The position of the chromosomes gives the best clue.

In Prophase, they are spread around the cell, and double stranded.

In Metaphase, the chromosomes are lined up on the spindle equator.

In Anaphase, the cromosomes are moving to opposite poles of the cell.

In Telophase, the two groups of chromosomes are separate, sometimes with a nuclear membrane.

8

Which one of the statements below best describes the mitotic index?

The mitotic shows the speed of cell division, which can be used as a tool to identify cancer.

It is calculated by dividing the number of cells doing mitosis by the total number of cells.

9

The microscope image shows cells in a tissue sample taken from a growth suspected of being cancerous.

What is the best estimate of the mitotic index of this tissue?
Assume that there are exactly 60 cells (for simplicity).

Skill: Determination of a mitotic index from a micrograph
There are 3 cells in stages of mitosis.
So the mitotic index = 3 divided by 60 cells total.
Keeping it simple = 1 / 20 or 0.05

10

Identify the stage of mitosis for the two cells X and Y.

Skill: Identification of phases of mitosis in cells viewed with a microscope or in a micrograph
(prophase, metaphase, anaphase and telophase).

Total Score:

Revision fun

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