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Biology 9700 > The Mitotic Cell Cycle > Flashcards

The Mitotic Cell Cycle Flashcards

1
Q

Why is DNA acidic?

A

Due to present phosphate groups

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2
Q

How is DNA neutralised in bacterial cells and in eukaryotic cells?

A

Spermidine and spermine as well as Ca and Mg ions
Eukaryotic cells have basic amino acid residues that can take up H ions (to form NH2) and form positive charges which neutralise the negative charges of the DNA.

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3
Q

When are chromosomes seen?

A

During nuclear division only as they are also intensely staining and very compact

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4
Q

What is the structure of a chromosome?

A

-DNA
-Histones
-Centromere
-Telomere
-Sister chromatids

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5
Q

What are histones?

A

Globular proteins whose role is to organise and condense the DNA molecule tightly so it fits into the nucleus

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6
Q

What other proteins are present in the nucleus?

A

Enzymes that are used in DNA replication and repair

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7
Q

What is a chromosome?

A

A long structure made up of coiled DNA associated with protein, by which genetic information is passed down from one generation to the next.

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8
Q

What forms when DNA is wrapped around a histone?

A

Nucleosome

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9
Q

Why is it essential to have identical sister chromatids?

A

So that during the nuclear division, each sister chromatid will go into a daughter cell to form genetically identical daughter cells.

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10
Q

During when are sister chromatids formed?

A

During the S phase in DNA replication

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11
Q

What is mitosis?

A

The nuclear division of a cell to form two genetically identical nuclei to go into two genetically identical daughter cells.

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12
Q

Mitosis is essential for:

A
  1. Growth
  2. Repair and replacement of worn out or dead cells/tissue
  3. Asexual reproduction
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13
Q

How is DNA packaged?

A
  1. The DNA molecule wraps around histones to form nucleosomes
  2. The ‘beaded’ DNA coils around itself in a solenoid structure to form chromatin
  3. Undergoes looping
  4. Undergoes further looping and coiling
  5. Chromatin becomes more compact and forms the characteristic chromosome that can be seen under an electron microscope
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14
Q

Why do the chromosomes exist as unwound structures in non-dividing cells?

A

So that the genes are accessible for transcription

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15
Q

What is the mitotic cell cycle?

A

A regulated sequence of events that occur between one cell division and the next with intermediate periods of growth.

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16
Q

What are the three phases of the mitotic cell cycle?

A
  1. Interphase
  2. Mitosis (nuclear division)
  3. Cytokinesis (cytoplasmic/cell division)
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17
Q

What triggers the movement from one phase to the next in the mitotic cell cycle?

A

Chemical signals known as cyclins

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18
Q

What phases exist in interphase?

A
  1. G1 phase
  2. G0 phase
  3. S phase
  4. G2 phase
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19
Q

What happens in G1 phase?
(The longest phase)

A

-cells increase in size
-produce RNA
-synthesize proteins required for replication
-organelles replicated
-some cells specialize and will not divide again

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20
Q

What happens in G0 phase?

A

-Cell be remain metabolically active/continue performing its usual functions but stop dividing
-This may be permanent (cell dies) or temporary (continues to divide later)

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21
Q

What happens at the G1 checkpoint?

A

Checks whether the cell is big enough and the environment stable enough to continue division.

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22
Q

What happens in the S phase?

A

-DNA replicates
-Goes from 2N to 4N
-The chromosomes now consist of two sister chromatids joined at a centromere

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23
Q

Which cells stop dividing at G0?

A

-Nerve cells
-Brain cells
-RBCs
-Heart cells

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24
Q

What happens at the G2 checkpoint?

A

Checks if the environment is suitable, the DNA replicated and if the cell is big enough. There is also error checking of replicated DNA and reparation.
There must also be sufficient energy reserves for mitosis. If absent, more energy reserves are produced and organelles replicated.

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25
Q

What happens during cytokinesis in animal cells?

A

The cell membrane invaginates at the centre under the action of microfilaments to form a cleavage furrow which will result in the complete separation of the two daughter cells.

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26
Q

What happens during cytokinesis in plant cells?

A

-Golgi apparatus releases carbohydrate containing vesicles (cellulose, hemicellulose, pectin) that line up at the cell plate
-Vesicles fuse together to form a cell plate
-Cell plate extends to the plasma membrane of the whole parent cell to form two daughter cells
-Carbohydrates in the vesicles form the middle lamella

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27
Q

What is the structure of telomeres?

A

-Made up of a repetition of base sequences that do not code for anything
-Found at the ends of DNA
-One sister chromatid has telomeres rich in cytosine while the other has telomeres rich in guanine

28
Q

How are the telomeres linked to ageing?

A

As time goes on, a cell continues to divide and with each new division the telomeres shorten until a point where the vital DNA is left unprotected and subsequently lost with every following cell division causing cell death.

29
Q

What helps to prevent the shortening of telomeres?

A

The enzyme telomerase which helps to rebuild lost bases at the ends of the telomeres after each division.

30
Q

What is the main function of telomeres?

A

-Lengthen DNA strands to ensure that the enzyme responsible for copying the genetic information can do so without the loss of vital genetic information as it is unable to copy to the very end of the DNA structure
-Prevent the loss of vital genetic information and subsequent cell death
-To allow continued replication of the cell and therefore cell division

31
Q

What are stem cells?

A

A group of unspecialised cells with the ability to divide an unlimited number of times and produce cells that have the ability to differentiate into other specialised cells. After one division of a stem cell, one daughter cell becomes specialised and the other remains a stem cell.

32
Q

Stem cells are characterised by what two features?

A
  1. Potency
  2. Self renewal
33
Q

What is potency?

A

The ability of the stem cell to differentiate into other specialized cells

34
Q

What is self renewal?

A

The ability of the stem cell to undergo numerous cycles of cell division while maintaining an unspecialised state

35
Q

What are the three types of potency in stem cells?

A
  1. Totipotency
  2. Pluripotency
  3. Multipotency
36
Q

What are totipotent stem cells?
Give an example of where they can be found.

A

Stem cells with the ability to differentiate into any type of cell including extra-embryonic cells (placental cells)
Found in a zygote

37
Q

What are pluripotent stem cells?
Give an example of where they can be found.

A

Stem cells with the ability to differentiate into any type of cell but have lost their totipotent ability to differentiate into extra-embryonic cells (placental cells)
Typically found as the inner mass of the blastocyst stage

38
Q

What is the other name for multipotent stem cells?

A

Adult stem cells/ Somatic stem cells

39
Q

What are multipotent/adult stem cells?

A

Stem cells that have lost their pluripotent characteristic and only have the ability to differentiate only into several types of cells in which they are found.

40
Q

What is the main purpose of adult stem cells?

A

They maintain and repair the tissues in which they are found.

41
Q

Name two potential uses of stem cells in making cells and tissues for medical therapies.

A
  1. Cell replacement therapy
  2. Tissue engineering
42
Q

What is the advantage of embryonic stem cells for tissue engineering?

A

They have the ability to differentiate into any type of cell

43
Q

What are the three main germ layers into which embryonic stem cells differentiate?

A
  1. Endoderm
  2. Mesoderm
  3. Ectoderm
44
Q

What are germ line cells and why are they set aside early into the development process?

A

These are the cells that produce the games and they are set aside early in the development process to ensure that any mutations that may occur with the adult stem cells may not be inherited.

45
Q

Name cells that never stop dividing for replacement.

A

-RBCs
-Skin cells
-Cells of the gut lining

46
Q

Name two cells that do not continue dividing throughout a person’s lifetime.

A

-Nerve cells
-Brain cells

47
Q

What is a clone?

A

The formation of a biologically identical individual from another organism

48
Q

What is development?

A

Process of progressive change through the lifetime of an organism

49
Q

What four processes are part of development?

A
  1. Cell division
  2. Growth
  3. Cell differentiation
  4. Morphogenesis
50
Q

Why does the cell required for cloning have to be taken at a very early stage of embryonic development?

A

At this stage, the telomeres would not have shortened significantly enough to result in a shorter lifespan

51
Q

What is the advantage of stem cell cloning?

A

It combats the issue of poor histocompatibility. As it combats the issue of histocompatibility that arises with transplants, there is no need for immune suppressants which could result in other disease. There is no chance of tissue rejection.

52
Q

What happens in embryonic stem cell cloning?

A

The nucleus of the ESC is transferred into an ovum whose nucleus has been removed. A mild electric shock induces the production of a new pre-embryo cell containing the patient’s DNA. After 30 days the inner mass of cells of the blastocyst in removed and cultured using appropriate growth factors to produce specific tissue

53
Q

What is the disadvantage of culturing such stem cell technologies?

A

-They require maintenance of disease-free environments
-Too long of a process
-A large amount of cells must be obtained in order for a large culture to form

54
Q

How are cancer cells different from all other cells?

A

They are immortal and do not respond to cell signals that instruct the halt of cell division. They divide uncontrollably and no longer perform the cell’s usual functions.

55
Q

What are carcinogens?

A

Any agent that may cause cancer

56
Q

Examples of carcinogens.

A

-Tar in tobacco smoke
-UV light
-X-rays
-Oncoviruses such as HPV

57
Q

What is a tumour?

A

An irregular mass of cells

58
Q

What are the two types of genes normally involved in controlling the cycle?

A
  1. Proto-oncogenes
  2. Tumour suppressor genes
59
Q

What is the function of proto-oncogenes?

A

They start the cell division process and are essential for normal cell development

60
Q

What is the function of tumour suppressor genes?

A

They switch off cell division, thereby preventing uncontrollable cell division when they have identified a fault or error in the DNA.

61
Q

What does the mutation of a proto-oncogene and tumour suppressor gene lead to?

A

Oncogenes that lead to uncontrollable cell division and the inability of the cell to stop it as the tumour suppressor genes are now off.

62
Q

What are mutagens?

A

An agent that causes genetic mutation

63
Q

What is apoptosis?

A

Programmed cell death

64
Q

What tumours spread throughout the body?

A

Malignant tumours

65
Q

How do tumours spread around the body?

A

Metastasis

Biology 9700 (4 decks)

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