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Biology Hope > Cell Division > Flashcards

Cell Division Flashcards

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1
Q

what is the cell cycle

A
  • highly ordered sequence of events that take place in a cell
  • formation of 2 genetically identical daughter cells
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2
Q

what is interphase

A
  • DNA is replicated
  • protein synthesis
  • mitochondria and chloroplast grow and divide
  • not a resting phase
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3
Q

what are the stages of interphase

A

G1- first growth phase
- proteins are synthesised - RNA, enzymes

S- Synthesis phase
- DNA is replicated in the nucleus

G2 - second growth phase
- cell continues to increase in size
- duplicated DNA is checked for errors

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4
Q

what is the G0 phase

A
  • resting phase
  • cell leaves the cycle temporarily or permanently
  • for differentiation - can no longer divide
  • error or damage in DNA
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5
Q

what are checkpoints

A
  • control mechanisms of the cell cycle
  • monitor and verify whether the processes at each phase of the cell cycle are correct before progessing
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6
Q

what is the G1 checkpoint

A
  • end of G1 phase and before S phase
  • if correct it triggers DNA replication or incorrect enters resting phase

Checks for
- cell size, nutrients, growth factors, DNA damage

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7
Q

what is the G2 checkpoint

A
  • end of G2 phase and before mitotic phase
  • if correct it can begin mitosis if not it enters the resting phase

Checks for
- cell size, DNA replication, DNA damage

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8
Q

what is the spindle assembly checkpoint

A
  • metaphase checkpoint
  • mitosis cannot proceed until the checkpoint has been passed

checks for
- chromosomes attached to spindle

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9
Q

what is mitosis

A
  • ensures that daughter cells produced are identical
  • growth, repair, replacement of tissues
  • asexual reproduction
  • prophase, metaphase, anaphase , telophase
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10
Q

what are chromosomes

A
  • each DNA molecule (chromosomes) is converted into two identical DNA molecules (chromatids)
  • two chromatids are joined at the centromere
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11
Q

what happens in prophase

A
  • chromosomes condense and are visible when stained
  • chromosomes consist of two sister chromatids identical joined at the centromere
  • protein microtubules form spindle fibres
  • centrosomes move towards opposite poles and spindle fibres attach
  • nuclear envelope is broken down
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12
Q

what happens in metaphase

A
  • spindle fibres continue to extend
  • chromosomes line up at the metaphase plate of the spindle
  • spindle fibres reach the chromosomes and attach to the centromeres
  • each sister chromatid is attached to a spindle fibre originating from opposite poles
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13
Q

what happens in anaphase

A
  • centromere holding together the sister chromatids separate and divide into two
  • spindle fibres shorten
  • chromosomes are pulled to opposite poles by spindle fibres
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14
Q

what happens in telophase

A
  • chromosomes arrive at apposite poles and condense
  • nuclear membranes begins to reform around each set of chromosomes
  • spindle fibres break down
  • chromosomes uncoil and nucleolus is formed
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15
Q

what is cytokinesis

A
  • division of the cell into separate cells
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16
Q

how does cytokinesis occur in animal cells

A
  • cleavage furrow forms around the middle of the cell
  • cell surface membrane is pulled inwards by the cytoskeleton until it is close enough to fuse around the middle forming two cells
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17
Q

how does cytokinesis occur in plant cells

A
  • vesicles in Golgi apparatus assemble on the metaphase plate
  • vesicles fuse with each other and the membrane divides into two
  • new sections of cell wall form along new sections of membrane
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18
Q

what is meiosis

A
  • production of haploid cells
  • sexual reproduction
  • two divisions
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19
Q

what happens in meiosis 1

A
  • pair of homologous chromosomes are separated into two cells
  • haploid cells
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20
Q

what happens in meiosis 2

A
  • pairs of chromatids in each daughter cell are separated forming 2 or more cells
  • produces 4 haploid daughter cells
21
Q

what happens in prophase 1

A
  • chromosomes condense, nuclear envelope breaks, spindle fibre formation
  • homologous chromosomes pair and form bivalents
  • crossing over
22
Q

what happens in metaphase 1

A
  • homologous pairs line up along the metaphase plate
  • independent assortment
23
Q

what happens in anaphase 1

A
  • homologous chromosomes pulled to opposite poles and the centromere doesn’t divide
  • chromatids break and re join
24
Q

what happens in telophase 1

A
  • chromosomes condense, spindle fibres break down, chromosomes uncoil
  • undergoes cytokinesis
25
Q

what happens in prophase 2

A
  • chromosomes condense and become visible, nuclear envelope breaks down, spindle fibre formation
26
Q

what happens in metaphase 2

A
  • individual chromosomes assemble along the metaphase plate
  • independent assortment
27
Q

what happens in anaphase 2

A
  • chromatids of individual chromosomes are pulled to opposite poles after division of the centromere
28
Q

what happens in telophase 2

A
  • chromatids assemble at the poles
29
Q

what happens in cytokinesis in meiosis

A
  • 4 genetically different haploid daughter cells
30
Q

what is crossing over

A
  • non sister chromatids exchange alleles
  • meiosis 1 homologous chromosomes pair up and are close in proximity
  • non-sister chromatids cross and entangle
  • crossing points called chiasmata
  • entanglement places stress on DNA molecules
  • section of chromatid from one chromosome may break and re join with another
31
Q

what is independent assortment

A
  • production of different combinations of alleles in daughter cells increasing genetic variation
32
Q

what are specialised cells

A
  • cells in multicellular organisms that are differentiated to carry out specific functions
33
Q

what is the structure of erythrocytes

A
  • flattened biconcave shape to increase surface area to volume ratio
  • no nuclei to maximise space for haemoglobin
  • flexible and can squeeze through narrow capillaries
34
Q

what is the structure of palisade cells

A
  • chloroplasts for photosynthesis
  • closely packed together to form a layer
  • thin walls to increase carbon dioxide diffusion rate
  • large vacuole to maintain pressure
35
Q

what are tissues and the types

A
  • collection of differentiated cells that have a specialised function
  • nervous tissue - adapted to support transmission of electrical impulses
  • epithelial tissue - cover internal and external body surfaces
  • muscle tissue - contract
  • connective tissue - holds tissues togetherorg
36
Q

what are organs and organ systems

A
  • collection of tissues adapted to form a particular function
  • digestive system
  • cardiovascular systemw
37
Q

what are stem cells

A
  • undifferentiated cells that undergo several cell divisions
  • found in the bone marrow
38
Q

what is potency and the types

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

totipotent - differentiate into any cell type
pluripotent - form all tissue types but not all organisms
multipotent - only form a range of cells within certain types of tissue

39
Q

how are erythrocytes replaced

A
  • multipotent cell divides to form proerythrocytes
  • cell undergoes changed and can form an erythrocyte
  • haemoglobin builds up in the cytoplasm
  • nucleus is ejected
  • cell forms a mature erythrocyte
40
Q

what are the sources of animal stem cells

A

embryonic and adult

41
Q

what are the sources of plant stem cells

A

meristems

42
Q

how are stem cells used in medicine

A

heart disease - muscle tissue is damaged
Alzheimer’s - brain cells are destroyed

burns - stem cells grown on biodegradable meshes to produce new skin

43
Q

what are the ethical obligations in stem cells

A
  • religious and moral objections - life begins at contraception = murder
  • lack of consensus as to when the embryo has rights
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Biology Hope (26 decks)

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