Cell Division Flashcards

1
Q

What happens in G1 phase of interphase?

A

Growth phase:

  • Protein synthesis
  • Cell increases in size
  • Organelles replicate
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2
Q

What happens in S phase in interphase?

A

Synthesis phase:

- DNA is replicated in the nucleus

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3
Q

What happens in G2 phase of interphase?

A

Second growth phase:

  • Cell continues to increase in size
  • Duplicated DNA is checked for errors
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4
Q

What happens in G0 phase?

A

The cell leaves the cycle either temporarily or permanently

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5
Q

What happens in the mitotic phase?

A
  • Mitosis (nucleus divides)

- Cytokinesis (cytoplasm divides)

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6
Q

Why might a cell leave the cycle?

A
  • Differentiation: A cell that becomes specialised is no longer able to divide
  • The DNA of a cell may be damaged
  • As you age, the number of these cells in your body increases: linked to age related diseases such as cancer and arthritis

A few types of cells that enter G0 can be stimulated to go back into the cycle, e.g. lymphocytes in an immune response

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7
Q

What happens at the G1 checkpoint?

A

End of G1 phase:

  • Cell size
  • Nutrients
  • Growth factors
  • DNA damage
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8
Q

What happens at the G2 checkpoint?

A

End of G2 phase:

  • Cell size
  • DNA replication
  • DNA damage
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9
Q

What happens at the spindle assembly checkpoint?

A

Point in mitosis:

- Chromosomes attached to spindle

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10
Q

What is mitosis necessary for?

A
  • Growth
  • Replacement
  • Repair of tissues in multicellular organisms
  • Asexual reproduction
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11
Q

What happens in prophase?

A
  • Chromatin fibres coil & condense = chromosomes
  • Nucleolus disappears
  • Nuclear envelope disappears
  • Spindle formation begins
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12
Q

What happens in metaphase?

A

Chromosomes line up on the equator

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13
Q

What happens in anaphase?

A
  • Centromeres divide

- Chromatids are separated and pulled to opposite poles

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14
Q

What happens in telophase?

A
  • Chromatids have reached poles = chromosomes
  • The 2 new sets of chromosomes assemble at each pole
  • Nuclear envelope reforms
  • Chromosomes uncoil
  • Nucleolus is formed
  • Cytokinesis begins
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15
Q

Describe cytokinesis in animals

A
  • A cleavage furrow forms around the middle of the cell
  • The cell-surface membrane is pulled inwards by the cytoskeleton until close enough to fuse around middle, forming 2 cells
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16
Q

Describe cytokinesis in plants

A
  • Vesicles from Golgi assemble on equator
  • Vesicles fuse with each other and membrane, dividing cell into 2
  • New cell wall forms along the new sections of membrane
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17
Q

What are alleles?

A

Different versions of the same gene

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18
Q

What happens in P1 in meiosis?

A
  • Chromosomes condense
  • Nucleolus disappears
  • Nuclear envelope disappears
  • Spindle formation begins
  • Homologous chromosomes pair up, forming bivalents
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19
Q

What can occur in P1 that causes genetic variation?

A
  • Crossing over, when bivalents get chromatids entangled and genetic material is transferred between them
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20
Q

What is chiasmata?

A

The points at which crossing over occurs (chromatids break and rejoin?)

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21
Q

What happens in M1 in meiosis?

A
  • Homologous pairs of chromosomes line up on the equator
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22
Q

What happens in A1 of meiosis?

A
  • Homologous chromosomes are pulled to opposite poles and chromatids stay joined together
  • Any potential chiasmata on recombinant chromatids are also pulled apart
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23
Q

What can occur in M1 that causes genetic variation?

A
  • Independent assortment, when the orientation of each homologous pair is random. It can result in many different combinations of alleles facing the poles
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24
Q

What happens in T1 of meiosis?

A
  • Chromosomes assemble at each pole
  • Nuclear membrane reforms
  • Chromosomes uncoil
  • Undergoes cytokinesis
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25
Q

What happens in P2 of meiosis?

A
  • Chromosomes condenses and become visible
  • Nuclear envelope breaks down
  • Spindle formation begins
26
Q

What happens in M2 of meiosis?

A
  • Individual chromosomes assemble on equator (like mitosis)

- Independent assortment occurs

27
Q

What happens in A2 of meiosis?

A
  • Chromatids of individual chromosomes are pulled to opposite poles after division of centromeres (like mitosis)
28
Q

What happens in T2 of meiosis?

A
  • Chromatids assemble at poles (like mitosis)
  • Chromosomes uncoil = chromatin
  • Nuclear envelope reforms
  • Nucleolus becomes visible
  • Cytokinesis = 4 haploid daughter cells, genetically different from each other
29
Q

Give 3 specialised animal cells

A
  • Erythrocytes
  • Neutrophils
  • Sperm cells
30
Q

How are erythrocytes specialised to carry out their function?

A
  • Flattened biconcave shape - increases SA:V ratio
  • No nuclei & not many other organelles - increases space available for haemoglobin
  • Flexible - squeeze through narrow capillaries
31
Q

How are neutrophils specialised to carry out their function?

A
  • Multi-lobed nucleus - squeeze through small gaps to get to site of infections
  • Granular cytoplasm contains many lysosomes
32
Q

How are sperm cells specialised to carry out their function?

A
  • Flagellum - movement
  • Mitochondria - supply energy needed to swim
  • Acrosome on head - contains digestive enzymes that digest protective layers around ovum
33
Q

Give 3 examples of specialised plant cells

A

1- Palisade cells
2- Root hair cells
3- Guard cells

34
Q

How are palisade cells specialised to carry out their function?

A
  • Chloroplasts - absorb large amounts of light for PHS
  • Chloroplasts can move within cytoplasm - absorb more light
  • Rectangular shape - closely pack together to form a continuous layer
  • Thin cell walls - increases rate of diffusion of CO2
  • Large vacuole - maintain turgor pressure
35
Q

How are root hair cells specialised to carry out their function?

A
  • Long extensions (root hairs) - increase SA to maximise uptake of water and minerals from soil
36
Q

How are guard cells specialised to carry out their function?

A
  • Can open and close depending on whether they lose or gain water
  • Cell wall thicker on one side - cell doesn’t change shape symmetrically as its volume changes
37
Q

Give 4 examples of specialised animal tissues

A
  • Squamous epithelium
  • Ciliated epithelium
  • Cartilage
  • Muscle
38
Q

How is squamous epithelium specialised to carry out its function?

A
  • Thin - 1 cell thick to allow rapid diffusion
39
Q

How is ciliated epithelium specialised to carry out its function?

A
  • Cilia - move together to move substances

- Goblet cells - release mucus to trap any unwanted particles present in the air

40
Q

How is cartilage specialised to carry out its function?

A
  • Contains elastin and collagen

- Prevents ends of bones rubbing together

41
Q

What is muscle?

A

A tissue that needs to be able to contract in order to move bones

42
Q

Give 3 examples of specialised plant tissue

A
  • Epidermis
  • Xylem tissue
  • Phloem tissue
43
Q

How is the epidermis specialised to carry out its function?

A
  • Covered by a waxy, waterproof cuticle - reduce water loss

- Stomata present- allow CO2, water vapour and O2 in/out

44
Q

How is xylem tissue specialised to carry out its function?

A
  • Lignin - structural support
45
Q

How is phloem tissue specialised to carry out its function?

A
  • Sieve tube cells -perforated end so cytoplasm connects from one cell to the next
46
Q

What is an organ?

A

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

47
Q

What is an organ system?

A

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

48
Q

What is differentiation?

A

The process of a cell becoming specialised

49
Q

What are stem cells?

A

Undifferentiated cells that have the potential to becomes a type of specialised cell

50
Q

What is potency?

A

A stem cell’s ability to differentiate into different cell types

51
Q

What is totipotent?

A
  • Can differentiate into any type of cell (embryo)
52
Q

What is pluripotent?

A
  • Can form all tissue types but not whole organisms

- They are present in early embryos

53
Q

What is multipotent?

A
  • Can only form a range of cells within a certain type of tissue (adult)
54
Q

Where are blood cells derived from?

A

Stem cells in the bone marrow

55
Q

What are the 2 types of stem cells?

A
  • Embryonic

- Tissue/adult

56
Q

What are embryonic stem cells?

A
  • Present at a very early stage of embryo development
  • Totipotent
  • After 7 days, a mass of cells form (blastocyst) and then they are in a pluripotent state
57
Q

What are adult stem cells?

A
  • Present throughout life from birth
  • Found in places like bone marrow
  • Multipotent
58
Q

Where are stem cells found in plants?

A

Meristematic tissue (meristems)

59
Q

Where is meristematic tissue found?

A

Wherever growth is occuring in plants

60
Q

Give 3 examples of potential stem cell uses

A

1- Heart disease
2- Type 1 diabetes
3- Spinal injuries

61
Q

Give 3 ethics points on using stem cells

A
  • Destruction of embryos
  • Religious objections
  • Moral objections