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C6 - Cell division Flashcards

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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
Creating two genetically identical daughter cells

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18
Q

What is mitosis important for?

A

Asexual reproduction
Growth
Tissue repair

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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 to chromosomes through mitosis

A
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22
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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23
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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24
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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25
What happens during telophase?
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
26
Light micrograph of mitosis of root tip cells
27
How does cytokinesis occur in animal cells?
Cleavage furrow forms in middle of cell Cell surface membrane pulled inwards by cytoskeleton until its close enough to fuse
28
How does cytokinesis occur in plants?
No cell wall Vesicles from Golgi apparatus begin to assemble Vesicles fuse with each other and cell surface membrane, dividing cell membrane into two
29
What is meiosis?
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
30
What are gametes?
Haploid sec cells produced in meiosis in organisms that reproduce asexually
31
What is a zygote?
Initial diploid cell formed when two gametes are joined by sexual reproduction (earliest stage of embryonic development)
32
What is reduction division?
Cell division resulting in the production of haploid cells from a diploid cell
33
What is a haploid?
Half the normal chromosome number, one chromosome of each type
34
What are homologous chromosomes?
Matching pair of chromosomes, one inherited from each parent
35
What are alleles?
Version of a gene
36
What is a diploid?
Normal chromosome number, two chromosomes of each type
37
What does mitosis produce?
Two genetically identical diploid daughter cells
38
What does meiosis produce?
Four genetically different haploid daughter cells
39
How are gametes produced?
Through meiosis
40
What are the two stages of meiosis called
Meiosis I Meiosis II
41
What happens during meiosis I?
Reduction division Pairs of homologous chromosomes separated into two cells Each cell contains only one full set of genes, haploid
42
What happens during meiosis II?
Pairs of chromatids separated forming two more cells Produces 4 haploid daughter cells
43
What happens in prophase 1
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
44
What is metaphase 1?
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
45
What is anaphase 1?
Homologous chromosomes are pulled to opposite poles Genetic variation arises from this new combination of alleles and sister chromatids not identical
46
What is telophase 1?
Chromosomes assemble at each pole Nuclear membrane reforms Chromosomes uncoil
47
What is prophase 2?
Chromosomes, consisting of two chromatids, condense Nuclear envelope breaks down Spindle formation begins
48
What is metaphase 2?
Individual chromosomes assemble on metaphase plate Chromosomes no longer identical so there is independent assortment causing more genetic variation
49
What is anaphase 2?
Chromatids of chromosomes pulled to opposite poles, after division of centromeres
50
What is telophase 2?
Chromatids assemble at poles Chromosomes uncoil and form chromatin Nuclear envelope reforms Nucleolus reappears
51
Why is meiosis significant
Production of haploid cells Genetic variation by independent assortment and crossing over
52
What are specialised cells?
Having a particular structure to serve a specific function
53
What is differentiation?
Process of a cell becoming differentiated, involving selective expression of genes in a cell's genome
54
How are erythrocytes specialised?
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
55
How are neutrophils specialised?
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
56
How are sperm cells specialised?
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
57
How are palisade cells specialised?
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
58
How are root hair cells specialised?
ROLE: present near growing tips -Long extension called root hairs: increase SA of cell maximising uptake of waters and minerals from soil
59
How are guard cells specialised?
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
60
What is a tissue?
Collection of differentiated cells that have specialised functions in an organism
61
What are the four main categories of tissues and how are they adapted for their function?
-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
62
How is squamous epithelium adapted?
ROLE: made up of specialised squamous epithelial cells -Very thin as its one cell thick: fast diffusion rates
63
How is ciliated epithelium adapted?
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)
64
How is cartilage adapted?
ROLE: connective tissue -Contains fibres of proteins: elastin and cartilage -Cartilage is a firm flexible connective tissue: prevents bones rubbing together
65
How is muscle adapted?
ROLE: contacting to move bones -Contains skeletal muscle fibres which contains myofibrils containing contractile proteins
66
How is the epidermis adapted?
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
67
How is xylem tissue adapted?
ROLE: vascular tissue responsible for transport of water and mineral ions -Walls strengthened with waterproof lignin: provides support
68
How is phloem tissue adapted?
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
69
What is an organ?
Collection of tissues that are adapted to perform a particular function in an organism
70
What are organ systems?
Group of organs working together to carry out a major function in the body
71
Name 3 examples of organ systems
Digestive system Cardiovascular system Gaseous exchange system
72
What are levels of organisation in multicellular organisms?
Specialised cells Tissues Organs Organ systems Whole organism
73
What is a stem cell
Undifferentiated cells with the potential to differentiate into a variety of specialised cell types of the organism
74
What are undifferentiated cells?
Unspecialised cell originating from mitosis or meiosis
75
What happens when stem cells become specialised?
Enter G0 phase of cell cycle Unable to divide
76
What is potency?
Stem cell's ability to differentiate into different cell types
77
What is totipotent?
Stem cell that can differentiate into any type of cell and form a whole organism
78
What is pluripotent?
Stem cell that can differentiate into any type of cell, but not form a whole organism
79
What is multipotent?
Stem cell that can only differentiate into a range of cell types within a certain tissue
80
Where are all stem cells that form blood cells derived from?
Bone marrow
81
What are the two types of animal stem cells
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
82
Where are plant stem cells found?
Meristematic tissue - found wherever growth is occurring pluripotent
83
What are some potential uses of stem cells?
-Heart disease -Type 1 diabetes -Parkinson's disease -Alzheimer's disease -Macular degeneration -Spinal injury
84
What are some current uses of stem cells?
-Treatment of burns -Drug trials -Developmental biology -Repair of damaged tissues -Treatment of neurological conditions
85
What are the ethical concerns surrounding stem cells?
-Religious objections -Belief that life begins at conception
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