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IB Biology > 1.6 Cell Cycle > Flashcards

1.6 Cell Cycle Flashcards

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1
Q

What is the cell cycle?

A

an ordered set of events which culminates in the division of a cell into two daughter cells

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2
Q

What are the 2 phases of the cell cycle?

A

Interphase

M Phase

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3
Q

What are the 3 sub-stages of interphase?

A

G1
S
G2

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4
Q

What is interphase?

A

The stage in the development of a cell between two successive divisions

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5
Q

What occurs at G1?

A

First intermediate gap stage in which the cell grows and prepares for DNA replication

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6
Q

What occurs at S?

A

Synthesis stage in which DNA is replicated

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7
Q

What occurs in G2?

A

Second intermediate gap stage in which the cell finishes growing and prepares for cell division

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8
Q

What is M phase?

A

The period of the cell cycle in which the cell and contents divide to create two genetically identical daughter cells

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9
Q

What two substages does M phase have?

A

mitosis

cytokinsesis

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10
Q

What is cytokinesis?

A

Cytoplasmic division, whereby cellular contents are segregated and the cell splits into two identical daughter cells

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11
Q

What type of reactions occur during interphase?

A

Interphase is an active period in the cell cycle when many METABOLIC reactions occur

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12
Q

What events have to occur during interphase for successful cell division?

A 
D NA replication
O rganelle duplication
C ell growth
T ranscription/translation
O btain nutrients
Respiration (cellular)
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13
Q

Why does interphase need DNA replication?

A

DNA is copied during the S phase of interphase

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14
Q

Why does interphase need organelle duplication?

A

Organelles must be duplicated for twin daughter cells

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15
Q

Why does interphase need cell growth?

A

Cytoplasmic volume must increase prior to division

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16
Q

Why does interphase need transcription/translation?

A

Key proteins and enzymes must be synthesised

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17
Q

Why does interphase need the cell to obtain nutrients?

A

Vital cellular materials must be present before division

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18
Q

Why does interphase need respiration?

A

ATP production is needed to drive the division process

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19
Q

How is DNA found in the nucleus?

A

DNA is usually loosely packed within the nucleus as unravelled chromatin

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20
Q

Why is DNA found in the form of unravelled chromatin in the nucleus?

A

In this unravelled form, the DNA is accessible to transcriptional machinery and so genetic information can be translated

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21
Q

In what cells is DNA organised as chromatin?

A

DNA is organised as chromatin in all non-dividing cells and throughout the process of interphase

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22
Q

What form is DNA found in prior to division? What process is used?

A

DNA is temporarily packaged into a tightly wound and condensed chromosome prior to division (via supercoiling)

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23
Q

Why is DNA put into its condensed form (chromosome) before division?

A

In this condensed form, the DNA is able to be easily segregated

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24
Q

Why is DNA being in the form of a chromosome not ideal?

A

DNA is inaccessible to transcriptional machinery

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25
Q

When is DNA organised as chromosomes?

A

DNA is organised as chromosomes during the process of mitosis

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26
Q

In what phase does DNA:

a) condense
b) decondense

A

a) prophase

b) telophase

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27
Q

What will chromosomes contain during the S phase of interphase?

A

As the DNA is replicated during the S phase of interphase, the chromosome will initially contain two identical DNA strands

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28
Q

What are genetically identical strands of DNA called?

A

These genetically identical strands are called sister chromatids

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29
Q

What holds sister chromatids together?

A

held together by a central region called the centromere

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30
Q

What happens to the chromatids after mitosis?

A

When these chromatids separate during mitosis, they become independent chromosomes, each made of a single DNA strand

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31
Q

What is mitosis?

A

Mitosis is the process of nuclear division, whereby duplicated DNA molecules are arranged into two separate nuclei

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32
Q

What is mitosis preceded by?

A

Mitosis is preceded by interphase

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33
Q

What four stages is mitosis divided into?

A

divided into four distinct stages: prophase, metaphase, anaphase, telophase

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34
Q

When does cytokinesis occur?

A

The division of the cell in two (cytokinesis) occurs concurrently with the final stage of mitosis (telophase)

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35
Q
  1. In what form is DNA present in, in interphase?
A

DNA is present as uncondensed chromatin (not visible under microscope)

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36
Q
  1. Where is DNA found during interphase?
A

DNA is contained within a clearly defined nucleus

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37
Q
  1. What happens to organelles during interphase/ in preparation for interphase?
A

Centrosomes and other organelles have been duplicated

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38
Q
  1. How does the cell look like in interphase?
A

Cell is enlarged in preparation for division

39
Q
  1. What does DNA look like during prophase?
A

DNA supercoils and chromosomes condense (becoming visible under microscope)

40
Q
  1. What are chromosomes composed of?
A

Chromosomes are comprised of genetically identical sister chromatids (joined at a centromere)

41
Q
  1. What role do centrosomes play in prophase?
A

Paired centrosomes move to the opposite poles of the cell and form microtubule spindle fibres

42
Q
  1. What happens to the nuclear membrane during prophase?
A

The nuclear membrane breaks down and the nucleus dissolves

43
Q
  1. What role do microtubule spindle fibres play in metaphase?
A

Microtubule spindle fibres from both centrosomes connect to the centromere of each chromosome

44
Q
  1. What does microtubule depolymerisation help happen in metaphase?
A

Microtubule depolymerisation causes spindle fibres to shorten in length and contract

This causes chromosomes to align along the centre of the cell (equatorial plane or metaphase plate)

45
Q
  1. What happens to chromatids in anaphase?
A

Continued contraction of the spindle fibres causes genetically identical sister chromatids to separate

46
Q
  1. What are chromatids considered to be once separated in anaphase?
A

Once the chromatids separate, they are each considered an individual chromosome in their own right

47
Q
  1. What do the chromatids do in anaphase?
A

The genetically identical chromosomes move to the opposite poles of the cell

48
Q
  1. What happens to the spindle fibres in telophase?
A

Once the two chromosome sets arrive at the poles, spindle fibres dissolve

49
Q
  1. What happens to chromosomes during telophase?
A

Chromosomes decondense (no longer visible under light microscope)

50
Q
  1. What happens to the nuclear membrane during telophase?
A

Nuclear membranes reform around each chromosome set

51
Q
  1. What is the final step to splitting the cell?
A

Cytokinesis occurs concurrently, splitting the cell into two

52
Q

Is cytokinesis the same in plant and animal cells?

A

NO

53
Q
  1. What is the first event during cytokinesis for animal cells that occurs after anaphase?

cytokinesis in animal cells

A

After anaphase, microtubule filaments form a concentric ring around the centre of the cell

54
Q
  1. What is the role of microfilaments in cytokinesis? What do they form?

cytokinesis in animal cells

A

The microfilaments constrict to form a cleavage furrow, which deepens from the periphery towards the centre

55
Q

3.What is the role of the cleavage furrow?

cytokinesis in animal cells

A

When the furrow meets in the centre, the cell becomes completely pinched off and two cells are formed

56
Q
  1. What is the separation of the two cells described as?

cytokinesis in animal cells

A

Because this separation occurs from the outside and moves towards the centre, it is described as centripetal

57
Q
  1. What is the first event of cytokinesis in plant cells?

cytokinesis in plant cells

A

After anaphase, carbohydrate-rich vesicles form in a row at the centre of the cell (equatorial plane)

58
Q
  1. What do the vesicles do? What is formed?

cytokinesis in plant cells

A

The vesicles fuse together and an early cell plate begins to form within the middle of the cell

59
Q
  1. What happens to the cell plate? What does it help do?

cytokinesis in plant cells

A

The cell plate extends outwards and fuses with the cell wall, dividing the cell into two distinct daughter cells

60
Q
  1. What is the separation described as?

cytokinesis in plant cells

A

Because this separation originates in the centre and moves laterally, it is described as centrifugal

61
Q

What is the mitotic index?

A

The mitotic index is a measure of the proliferation status of a cell population (i.e. the proportion of dividing cells)

62
Q

When might the mitotic index be higher?

A

The mitotic index may be elevated during processes that promote division, such as normal growth or cellular repair

63
Q

Why might the mitosis index be important?

A

It also functions as an important prognostic tool for predicting the response of cancer cells to chemotherapy

64
Q

What do cells that are undergoing mitosis look like?

A

Cells undergoing mitosis will lack a clearly defined nucleus and possess visibly condensed chromosomes

65
Q

How do you calculate the mitotic index?

A

number of cells in mitosis / total number of cells

66
Q

What are cyclins?

A

Cyclins are a family of regulatory proteins

67
Q

What is the role of cyclins?

A

control the progression of the cell cycle

68
Q

What do cyclins activate?

A

Cyclins activate cyclin dependent kinases (CDKs)

69
Q

What is the role of CDKs?

A

control cell cycle processes through phosphorylation

70
Q
  1. What happens between a cyclin and CDK?
A

When a cyclin and CDK form a complex, the complex will bind to a target protein and modify it via phosphorylation

71
Q
  1. What happens to the target protein?
A

The phosphorylated target protein will trigger some specific event within the cell cycle (e.g. centrosome duplication, etc.)

72
Q
  1. What happens after the cyclin has completed its role?
A

After the event has occurred, the cyclin is degraded and the CDK is rendered inactive again

73
Q

Why do cyclin concentrations need to be tightly regulated?

A

Cyclin concentrations need to be tightly regulated in order to ensure the cell cycle progresses in a proper sequence

74
Q

Are cyclins specific?

A

YES

Different cyclins specifically bind to, and activate, different classes of cyclin-dependent kinases

75
Q

When will cyclin levels peak?

A

Cyclin levels will peak when their target protein is required for function and remain at lower levels at all other times

76
Q

What are tumours?

A

Tumours are abnormal cell growths resulting from uncontrolled cell division and can occur in any tissue or organ

77
Q

What are cancers?

A

Diseases caused by the growth of tumours are collectively known as cancers

78
Q

What is a mutagen?

A

A mutagen is an agent that changes the genetic material of an organism (either acts on the DNA or the replicative machinery)

79
Q

What 3 types of mutagens can there be?

A

physical, chemical and biological

80
Q

What are examples of physical mutagens?

A

Sources of radiation including X-rays (ionising), ultraviolet (UV) light and radioactive decay

81
Q

What are examples of chemical mutagens?

A

DNA interacting substances including reactive oxygen species (ROS) and metals (e.g. arsenic)

82
Q

What are examples of biological mutagens?

A

Viruses, certain bacteria and mobile genetic elements (transposons)

83
Q

What are mutagens called when they lead to the formation of cancer?

A

Mutagens that lead to the formation of cancer are further classified as carcinogens

84
Q

What is an oncogene?

A

An oncogene is a gene that has the potential to cause cancer

85
Q

What are most cancers caused by? give name of 2 factors

A

Most cancers are caused by mutations to two basic classes of genes – proto-oncogenes and tumour suppressor genes

86
Q

What do proto-oncogenes code for?

A

code for proteins that stimulate the cell cycle and promote cell growth and proliferation

87
Q

What do tumour suppressor genes code for?

A

code for proteins that repress cell cycle progression and promote apoptosis

88
Q

What has to happen to a proto-oncogene in order for it to cause cancer, what is it then called?

A

When a proto-oncogene is mutated or subjected to increased expression it becomes a cancer-causing oncogene

89
Q

What can tumour suppressor genes also be called and why?

A

Tumour suppressor genes are sometimes referred to as anti-oncogenes, as their normal function prevents cancer

90
Q

What is metastasis?

A

Metastasis is the spread of cancer from one location (primary tumour) to another, forming a secondary tumour

91
Q

What does it mean if tumour cells are benign?

A

when tumour cells remain in their original location

92
Q

What does it mean if tumour cells are malignant?

A

when tumour cells spread and invade neighbouring tissue (malignant)

93
Q

What type of cells are secondary tumours made out of?

A

Secondary tumours are made up of the same type of cell as the primary tumour – this affects the type of treatment required

E.g. If breast cancer spread to the liver, the patient has secondary breast cancer of the liver (treat with breast cancer drugs)

94
Q

What happens to the chromatids after mitosis?

A

When these chromatids separate during mitosis, they become independent chromosomes, each made of a single DNA strand

IB Biology (38 decks)

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