1.6 Cell division Flashcards

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1
Q

What do all cells go through before undergoing mitosis?

A

The cell cycle

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2
Q

What are the phases in the cell cycle?

A

Interphase then Mitosis

Interphase: G1, S, G2

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3
Q

What percentage of the cell cycle does cell division make up?

A

5-10% of the cell cycle

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4
Q

What processes occurs in interphase? What is the mnemonic?

A

DOCTER

DNA replication - Dna is copied during the S phase of interphase

Organelles duplicate - Organelles must be duplicated for twin daughter cells

Cell grows - Cytoplasmic volume must increase prior to division

Transcription + Translation - Key proteins and enzymes must be synthesised

Obtained nutrients - vital cellular materials must be present before division

Respiration - ATP production is needed to drive the division process

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5
Q

What is interphase in simple words?

A

Phase of the cell cycle where the cell is not dividing but is undergoing G1, S, and G2 phase

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6
Q

What is mitosis and cytokinesis in simple words?

A

Mitosis: The nuclear division that produces genetically identical daughter cells

Cytokinesis: cytoplasmic division following mitosis

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7
Q

What happens in G0 Phase?
What type of cells remain in G0 phase or a very long time, or even indefinitely?
What type of cell does not undergo G0 phase?

A
  • differentiation
  • apoptosis (programmed cell death)
  • Senescence (no longer divide)

Specialised cells because once damaged, they are done for, and are not made more of.

Stem cells do not undergo G0 phase

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8
Q

What do checkpoints do in the cell cycle? What is the purpose?

A

Checkpoints control the mechanism of the cell cycle. They verified that the processes that should occur each stage has been completed correctly before the cell is allowed to move onto the next stage.

  • prevent uncontrolled division
  • detect any DNA damage
  • ensure DNA has replicated
  • ensure cell cycle is not reversed
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9
Q

What are the two main types of tumor? What is metastasis?

A

Benign - tumours that have not spread around the body
Malignant - tumours that can spread around the body

Metastasis - a primary tumor spreading around the body to form a secondary tumor

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10
Q

What is the Hayflick limit?

A

Hayflick limit is that cells should normally only undergo a certain number of cycles (~50 divisions). If cell division becomes uncontrolled, then a tumor can form which may be malignant (cancerous)

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11
Q

What is the Proto-oncogenes and oncogenes gene?
Which is good which is bad? How can proto-oncogenes gene turn into oncogenes gene? How is the p53 tumour suppressor gene involved?

A

Proto-oncogenes help regulate cell division by coding for proteins that help regulate cell growth and division.

If proto-oncogenes mutated, they may become oncogenes which can cause cells to fail to undergo apoptosis and instead keep dividing, leaving to a tumour.

The p53 gene is a very important tumour suppressor gene - it triggers the G1 checkpoint and the G2 checkpoint preventing uncontrolled division of cells. p53 will become inactivated with oncogene.

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12
Q

What is a mutation? What are carcinogens?

A

Mutation is a random change in the structure of DNA (sequence)

Carcinogens are chemicals and agent that can cause cancer.

When you have a longer lifespan you have more exposure to carcinogens and increases the chance of tumor

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13
Q

What are cyclins and CDKs (cyclin-dependent kinases)?

A

They are cell cycle regulatory proteins. CDK, cyclin-dependent kinases are enzymes that phosphorylate proteins.

CDKs are enzymes that control the cell cycle checkpoints. They are activated by cyclins which bind to the CDK forming a CDK complex.
CDK complexes phosphorylate and activate proteins at checkpoints, allowing to cell to progress through the cell cycle.

1) cycling binds and activate CDK
2) CDK activates target protein to regulate cell cycle
3) Cyclins destroyed when they’re not needed by enzymes breaking them down

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14
Q

What are the 4 main types of cyclin in human cells? What are each responsible for?

A

Cyclin D - triggers cells to move from G0 to G1 and from G1 to S phase

Cyclin E - prepares the cell for DNA replication in S phase

Cyclin A - activates DNA replication inside the nucleus in S phase

Cyclin B - promotes the assembly of the mitotic spindle (spindle fibres) and other tasks in the cytoplasm to prepare for mitosis.

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15
Q

Which type of reproduction is mitosis an example of? What does it produce?

A

Asexual reproduction (produces genetically identical cells)

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16
Q

What are the functions of mitosis?

A

Growth - all multicellular organisms grow by producing more cells that are genetically identical to each other and to the parent cell from which they arose by mitosis

Tissue repair - wounds heal when growth factors, secreted by platelets and macrophages (white blood cells) and damaged cells of the blood-vessel walls, stimulate the proliferation of endothelial and smooth muscle cells to repair damaged blood cells.

Replacement of cells - cells become worn out and need replacing, such as those lining the gut, which in humans are replaced each day.

17
Q

What is the complex of DNA and histone proteins called? Where can it be found in eukaryotes?

A

Chromatin and is present within the nucleus

18
Q

What happens to chromatin during interphase (G1, S, G2) of the cell cycle?

A

Chromatin is the condensed so that DNA can be accessed relatively easily by cellular machinery (such as proteins that read and copy DNA), which is important in allowing the cell to grow and function.

19
Q

What occurs in the S phase?

A

Two copies of a chromosome are called sister chromatids. The sister chromatids are identical to one another and are attached to each other by proteins called cohesins. Attachment between sister chromatids is tightest at the centromere.

20
Q

How many chromosome is two chromatids considered as?

A

One chromosome because they are connected to one centromere. But are considered as separate chromosomes after they are pulled apart.

21
Q

What is the difference between centromeres, centrosomes and centrioles?

A

Centrosome: area of the cell cytoplasm where the centrioles are

Centriole: the bundles of microtubules that form the spindle fibres for nuclear division

Centromere: The region where sister chromatids are attached within a chromosome.

22
Q

What are the 4 main stages of mitosis? What is the mnemonic?

A

PMAT

Prophase - chromosomes condense, nucleolus disappears, nuclear envelope/membrane breaks down, centrioles move to opposite poles of the cell to form spindle fibers.

Metaphase - chromosomes lineup along the equator of the cell, chromosomes become attached to the spindle fibers at their centromeres. Checkpoint checks this.

Anaphase - each sister chromatid is pulled to the opposite poles of the cell that by their centromere (v shaped), spindle fibers contract with the help of motor proteins, each chromatid is now referred to as a separate chromosome.

Telophase - chromosomes decondenses, spindle fibres disintegrate, nuclear envelope reforms around chromosomes, nucleolus reappears.

23
Q

What occurs in cytokinesis?

A

1) Rest of cell is split to create two new daughter cells with identical nuclei
2) In animal cells, the plasma membrane is pulled inwards around the equator of the cell by a ring of contractile protein (actin). When the actin reaches the centre, the cell is pinched apart into two daughter cells.
3) 2 new genetically identical daughter cells are formed.
4) They then independently enter G1 phase of interphase and either continue the cycle and divide again or enger G0 phase and differentiate.

24
Q

What protein pulls the plasma membrane inwards around the equator of the cell?

A

A ring of contractile protein (actin)

25
Q

What is cytokinesis like in plant cells?

A

The golgi apparatus and associated secretory vesicles assemble in the centre of the cell. The vesicles fuse with each other and the cell surface membrane, dividing the cell in two. New sections of cellulose cell wall then form along the new sections of membrane. Some vesicles remain intact and make connecting channels (plasmadesmata) through the new cell wall.

26
Q

What must you mention when you refer to daughter cells?

A

That they are genetically identical

27
Q

How to measure mitotic index? What does it tell us?

A

The mitotic index is the ratio between the number of cells in mitosis in a tissue and the total number of observed cells.

Mitotic index = number of cells in mitosis/total number of cells