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biology > C6 - Cell division > Flashcards

C6 - Cell division Flashcards

1
Q

What are the phases of the cell cycle?

A

Interphase
Mitotic phase

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2
Q

What is interphase

A

Growth period of the cell consisting of stages G1, S and G2, between cell division

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3
Q

What happens during interphase?

A

-DNA replicated and checked for errors in the nucleus
-Protein synthesis occurs in the cytoplasm
-Mitochondria (and chloroplasts) grow and divide
-Normal metabolic processes of cells also occur

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4
Q

What is the G1 stage?

A

First growth stage - proteins which synthesise organelles are produced and organelles replicate, the cell increases in size

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5
Q

What is the S phase?

A

Synthesis phase - DNA is replicated in the nucleus

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6
Q

What is the G2 phase

A

Second growth phase - cell continues to increase in size, energy stores are increased and duplicated DNA is checked for errors

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7
Q

What is the mitotic phase

A

Period of cell division consisting of mitosis and cytokinesis

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8
Q

What happens during mitosis

A

Nucleus divides

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9
Q

What happens during cytokinesis

A

Cytoplasm divides and two new cells are produced

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10
Q

What is G0

A

Phase when cell leaves the cycle permanently or temporarily?

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11
Q

What are the reasons for a cell entering G0

A

-Differentiation: cell that becomes specialised to carry out a specific function is no longer able to divide
-DNA of cell may be damaged: no longer viable
-Aging: growing number of senescent cells

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12
Q

What are checkpoints?

A

Control mechanisms of the cell cycle

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13
Q

Where do checkpoints occur?

A

G1 checkpoint- end of G1 phase, before entry into S phase
G2 checkpoint- end of G2 phase, before mitotic phase
Spindle assembly (metaphase) checkpoint- when all chromosomes attached to spindles and aligned

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14
Q

What does G1 checkpoint check?

A

Cell size
Nutrients
Growth factors
DNA damage

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15
Q

What does G2 checkpoint check

A

Cell size
DNA replication
DNA damage
-If passed, signals beginning of mitosis

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16
Q

What does spindle assembly checkpoint check?

A

Chromosome attachment to spindle
-Mitosis cannot proceed if checkpoint isn’t passed

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17
Q

What is mitosis?

A

Nuclear division stage in cell cycle

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18
Q

What is mitosis important for?

A

Creating two genetically identical daughter cells
Asexual reproduction

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19
Q

What has to happen before mitosis can occur? (chromosomes)

A

Interphase - DNA in nucleus replicated
Each chromosome is converted into two identical DNA molecules called chromatids
Chromatids joined together at region called centromere

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20
Q

What are the four stages of mitosis

A

Prophases
Metaphase
Anaphase
Telophase

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21
Q

What happens during prophase?

A

1) Chromatin fibres coil and condense to form chromosomes
2) Nucleolus disappears
3) Nuclear membrane begins to break down
4) Protein microtubules form spindle-shaped structures linking poles of cell
-Animal and some plants: centrioles migrate to poles and form spindles
5) Spindle fibres attach to specific areas on centromeres and move chromosome to centre of cell
5) By end, nuclear envelope disappeared

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22
Q

What happens during metaphase?

A

1) Chromosomes moved by spindle fibres to form a plane in the centre of the cell (metaphase plate)
2) Held in position

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23
Q

What happens during anaphase?

A

1) Centromeres holding together pairs of chromatids in each chromosome divide
2) Chromatids separated and pulled to opposite poles by shortening spindle fibres

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24
Q

What happens during telophase?

A

1) Chromatids have reached poles and are called chromosomes
2) Two new sets of chromosomes assemble at each pole
3) Nuclear envelope reforms around them

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25
Q

What is cytokinesis

A

Cell division stage in the mitotic phase of the cell cycle that results in the production of two identical daughter cells

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26
Q

How does cytokinesis occur in animal cells?

A

Cleavage furrow forms in middle of cell
Cell surface membrane pulled inwards by cytoskeleton until its close enough to fuse

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27
Q

What is meiosis?

A
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28
Q

How does cytokinesis occur in plants?

A

No cell wall
Vesicles from Golgi apparatus begin to assemble
Vesicles fuse with each other and cell surface membrane, dividing cell membrane into two

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29
Q

What is meiosis?

A

Form of cell division where the nucleus divides twice resulting in halving of the chromosome number and producing four haploid cells from one diploid cell

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30
Q

What are gametes?

A

Haploid sec cells produced in meiosis in organisms that reproduce asexually

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31
Q

What is a zygote?

A

Initial diploid cell formed when two gametes are joined by sexual reproduction (earliest stage of embryonic development)

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32
Q

What is reduction division?

A

Cell division resulting in the production of haploid cells from a diploid cell

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33
Q

What is a haploid?

A

Half the normal chromosome number, one chromosome of each type

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34
Q

What are homologous chromosomes?

A

Matching pair of chromosomes, one inherited from each parent

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35
Q

What are alleles?

A

Version of a gene

36
Q

What is a diploid?

A

Normal chromosome number, two chromosomes of each type

37
Q

What does mitosis produce?

A

Two genetically identical diploid daughter cells

38
Q

What does meiosis produce?

A

Four genetically different haploid daughter cells

39
Q

How are gametes produced?

A

Through meiosis

39
Q

What are the two stages of meiosis called

A

Meiosis I
Meiosis II

40
Q

What happens during meiosis I?

A

Reduction division
Pairs of homologous chromosomes separated into two cells
Each cell contains only one full set of genes, haploid

41
Q

What happens during meiosis II?

A

Pairs of chromatids separated forming two more cells
Produces 4 haploid daughter cells

42
Q

What happens in prophase 1

A

Chromosomes condense
Nuclear envelope disintegrates
Nucleolus disappears
Spindle formation begins
-Homologous chromosomes pair up forming bivalents
-Moving chromosomes through cytoplasm causes chromotids entangling, crossing over

43
Q

What is metaphase 1?

A

Homologous pairs of chromosomes moved by spindle fibres to form a plane in the centre of the cell (metaphase plate)
Orientation of homologous pairs is random and independent
Independent assortment results in genetic variation

44
Q

What is anaphase 1?

A

Homologous chromosomes are pulled to opposite poles
Sections of DNA on sister chromatids became entangled during crossing over
They break off and rejoin, sometime resulting in exchange of DNA (chiasmata -points where they break off)
When exchange occurs, recombinant chromatids formed with genes exchanged
Genetic variation arises from this new combination of alleles and sister chromatids not identical

45
Q

What is telophase 1?

A

Chromosomes assemble at each pole
Nuclear membrane reforms
Chromosomes uncoil

46
Q

What is prophase 2?

A

Chromosomes, consisting of two chromatids, condense
Nuclear envelope breaks down
Spindle formation begins

47
Q

What is metaphase 2?

A

Individual chromosomes assemble on metaphase plate
Chromosomes no longer identical so there is independent assortment causing more genetic variation

48
Q

What is anaphase 2?

A

Chromatids of chromosomes pulled to opposite poles, after division of centromeres

49
Q

What is telophase 2?

A

Chromatids assemble at poles
Chromosomes uncoil and form chromatin
Nuclear envelope reforms
Nucleolus reappears

50
Q

What are specialised cells?

A

Having a particular structure to serve a specific function

51
Q

What is differentiation?

A

Process of a cell becoming differentiated, involving selective expression of genes in a cell’s genome

52
Q

How are erythrocytes specialised?

A

ROLE: transporting oxygen around body (rbc)
-Flattened biconcave shape: increases SA:V ratio, increasing rate of diffusion
-No nuclei and lacking some organelles: increasing space available for haemoglobin (carries O2)
-Flexible: enables them to squeeze through narrow capillaries

53
Q

How are neutrophils specialised?

A

ROLE: immune system (wbc)
-Multi-lobed nucleus: easier to squeeze through small gaps to reach site of infection
-Granular cytoplasm contains lysosomes: contain enzymes to attack pathogens

54
Q

How are sperm cells specialised?

A

ROLE: deliver genetic material to female gamete (male gametes)
-Tail/flagellum: capable of movement
-Contain many mitochondria: supply energy needed to swim
-Acrosome on head contains digestive enzymes: released to digest protective layer surrounding ovum, enabling sperm to penetrate and fertilise

55
Q

How are palisade cells specialised?

A

ROLE: present in mesophyll
-Contain chloroplasts: absorb large amounts of light for photosynthesis
-Rectangular box shaped cells: can be closely packed together
-Thin cell walls: increasing rate of diffusion of CO2
-Large vacuole: maintains turgor pressure
-Chloroplasts move within cytoplasm: to absorb more light

56
Q

How are root hair cells specialised?

A

ROLE: present near growing tips
-Long extension called root hairs: increase SA of cell maximising uptake of waters and minerals from soil

57
Q

How are guard cells specialised?

A

ROLE: on surface of leaves
-Form stomata: necessary for CO2 to enter plant
-When guard cells lose water and become less swollen, they change shape, closing to prevent water loss
-Cell wall thicker on one side: cell does not change shape symmetrically as its volume changes

58
Q

What is a tissue?

A

Collection of differentiated cells that have specialised functions in an organism

59
Q

What are the four main categories of tissues and how are they adapted for their function?

A

-Nervous tissue: adapted to support transmission of electrical impulses
-Epithelial tissue: adapted to cover internal and external body surfaces
-Muscle tissue: adapted to contract
-Connective tissue: adapted to hold tissues together/ as a transport medium

60
Q

How is squamous epithelium adapted?

A

ROLE: made up of specialised squamous epithelial cells
-Very thin as its one cell thick: fast diffusion rates

61
Q

How is ciliated epithelium adapted?

A

ROLE: made up of ciliated epithelial cells
-Hair-like structure that move in a rhythmic manner
(+goblet cells secreting mucus to sweep away particles in trachea)

62
Q

How is cartilage adapted?

A

ROLE: connective tissue
-Contains fibres of proteins: elastin and cartilage
-Cartilage is a firm flexible connective tissue: prevents bones rubbing together

63
Q

How is muscle adapted?

A

ROLE: contacting to move bones
-Contains skeletal muscle fibres which contains myofibrils containing contractile proteins

64
Q

Name two tissues in plants and how they are adapted?

A

Epidermis tissue: adapted for cover plant surfaces
Vascular tissue: adapted for transport of water and nutrients

65
Q

How is the epidermis adapted?

A

ROLE: single layer of closely packed cells covering surface of plants
-Covered by waxy, waterproof cuticle: reduce water loss
-Stomata are present: allow gas exchange

66
Q

How is xylem tissue adapted?

A

ROLE: vascular tissue responsible for transport of water and mineral ions
-Walls strengthened with waterproof lignin: provides support

67
Q

How is phloem tissue adapted?

A

ROLE: vascular tissue responsible for transport of organic nutrients from leaves and stems to place they are required
-Composed of sieve tubes separated by sieve plates

68
Q

What is an organ?

A

Collection of tissues that are adapted to perform a particular function in an organism

68
Q

What are organ systems?

A

Group of organs working together to carry out a major function in the body

69
Q

Name 3 examples of organ systems

A

Digestive system
Cardiovascular system
Gaseous exchange system

70
Q

What are levels of organisation in multicellular organisms?

A

Specialised cells
Tissues
Organs
Organ systems
Whole organism

71
Q

What is a stem cell

A

Undifferentiated cells with the potential to differentiate into a variety of specialised cell types of the organism

72
Q

What are undifferentiated cells?

A

Unspecialised cell originating from mitosis or meiosis

73
Q

What happens when stem cells become specialised?

A

Enter G0 phase of cell cycle
Unable to divide

73
Q

What is potency?

A

Stem cell’s ability to differentiate into different cell types

74
Q

What is totipotent?

A

Stem cell that can differentiate into any type of cell and form a whole organism

75
Q

What is pluripotent?

A

Stem cell that can differentiate into any type of cell, but not form a whole organism

76
Q

What is multipotent?

A

Stem cell that can only differentiate into a range of cell types within a certain tissue

77
Q

Where are all stem cells that form blood cells derived from?

A

Bone marrow

78
Q

What are the two types of animal stem cells

A

Embryonic stem cells: present at very early stage of embryo development - totipotent, from blastocyst (7days) to birth - pluripotent
Adult stem cells: present from birth - multipotent

79
Q

Where are plant stem cells found?

A

Meristematic tissue - found wherever growth is occurring
pluripotent

80
Q

What are some potential uses of stem cells?

A

-Heart disease
-Type 1 diabetes
-Parkinson’s disease
-Alzheimer’s disease
-Macular degeneration
-Spinal injury

81
Q

What are some current uses of stem cells?

A

-Treatment of burns
-Drug trials
-Developmental biology

82
Q

What are the ethical concerns surrounding stem cells?

A

-Religious objections
-Belief that life begins at conception

biology (13 decks)

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