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ocr a level biology > chapter 6 - cell division > Flashcards

chapter 6 - cell division Flashcards

(49 cards)

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1
Q

interphase - G1

A

period of cell growth before the DNA is duplicated

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2
Q

interphase - S

A

period when the DNA is duplicated

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3
Q

interphase - G2

A

period after DNA is duplicated, cell prepares for division

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4
Q

prophase

A

chromosomes become visable as they shorten and thicken

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5
Q

metaphase

A

chromosomes line up at the equator

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6
Q

anaphase

A

chromatids pull apart to opposite ends of the cell

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7
Q

telophase

A

a nuclear envelope reforms around chromosomes

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8
Q

cytokinesis

A

the cytoplasm divides into two and each cell contains a full set of chromosomes identical to parent cell

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9
Q

cytokinesis in animal cells

A

cell division involves furrowing and cleavage of cytoplasm; cytokinesis starts at the edge of the cell

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10
Q

cytokinesis in plant cells

A

cell division involves the formation of a cell plate; cytokinesis starts from the middle of the cell

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11
Q

importance of mitosis

A
  • asexual reproduction
  • growth in multicellular organisms
  • repair of tissues
  • replacement of cells
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12
Q

purpose of checkpoints

A
  • prevent uncontrolled division, leading to tumours
  • detect and repair damage to DNA
  • ensure cycle is not reversed
  • DNA is only copied once during each cell cycle
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13
Q

G0 (resting phase)

A

cells leave cell cycle due to
- cell differentiation; once specialised some cells won’t undergo mitosis again
- if DNA is damaged

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14
Q

G1 checkpoint

A

checks for cell size, nutrients, growth factors, DNA damage

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15
Q

G2 checkpoint

A

checks for DNA replication, cell size

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16
Q

spindle assembly checkpoint

A

checks that chromosomes are attached to spindle

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17
Q

mitosis in yeast cells

A
  • the nucleus divides by mitosis
  • cell swells on the side (bud develops)
  • one nucleus moves into the swelling bud
  • unequal distribution of cytoplasm
  • cell wall forms
  • 2 new cells formed
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18
Q

binary fission in prokaryotic cells

A
  • cell grows to its limit
  • DNA replication
  • two new loops of DNA pulled to opposite ends of the cell
  • cell divides into 2
  • a new cell wall forms
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19
Q

stem cells

A

undifferentiated cells that can undergo cell division and have the potential to differentiate

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20
Q

totipotent

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A

can differentiate into any type of cell

21
Q

pluripotent

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A

can form all tissue types but not whole organisms

22
Q

multipotent

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A

can form a range of cells within a certain type of tissue

23
Q

unipotent

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A

can give rise to only one cell type

24
Q

red blood cell

25
white blood cell (phagocyte)
neutrophil
26
diploid
normal chromosome number; two chromosomes of each type - one inherited from each parent
27
haploid
half the normal chromosome number; one chromosome of each type
28
interphase
DNA replicates so each chromosome consists of two sister chromatids
29
early prophase I
the chromosomes condense, super coil and become visible
30
late prophase I
homologous chromosomes pair up forming a bivalent
31
metaphase I
the bivalents randomly line up at the equator and the spindle fibres attach to them at their centromeres
32
anaphase I
the homologous chromosomes of each bivalent are pulled apart by the spindle fibres towards the poles (each chromosome consists of two chromatids)
33
telophase I
in animal cells the nuclear envelope will reform. cytokinesis may occur and the cell will split. most plant cells progress straight to metaphase II
34
prophase II
everything from now on happens in two nuclei: the chromosomes recondense; each consists of two chromatids
35
metaphase II
the chromosomes randomly line up at the equator
36
anaphase II
the chromosomes are pulled apart by the spindle fibres
37
telophase II
the chromatids (now called chromosomes) reach the poles and decondense, the nuclear envelope reforms, forming four separate nuclei
38
causes of variation: crossing over
- occurs during prophase I - in bivalents, chromatids can break and re-join at the chiasmata (points where homologous chromosomes are attracted to each other) - this produces a different combination of alleles on each chromatid
39
causes of variation: independant assortment
- occurs during metaphase I - bivalents orientate themselves randomly at the equator - this means that any combination of maternal and paternal chromosomes could end up in each gamete produced - the number of combinations for n chromosomes is 2n
40
causes of variation: independant assortment of chromatids
- occurs during metaphase II - chromatids orientate themselves randomly at the equator so the chromatids could be facing either pole - this is important because due to crossing over, the sister chromosomes are no longer identical
41
causes of variation: random fertilisation
any one of about 300 million genetically different sperm can fertilise the egg
42
adaptations of erythrocytes
- lose nucleus - contain haemoglobin - biconcave shape
43
adaptations of neutrophils
- contain lots of lysosomes - multilobed nucleus
44
adaptations of squamous eqithelial cells
- flat and thin - basement membrane made of collagen and glycoproteins
45
adaptations of ciliated epithelial cells
- column shaped cells - have cilia - many mitochondria
46
adaptations of sperm cells
- long, thin shape - has undulipodium (flagellum) - nucleus contains one set of chromosomes - many mitochondria - has acrosomes (special lysosomes)
47
adaptations of palisade cells
- thin cellulose cell walls - contain lots of chloroplasts - chloroplasts moved by cytoskeleton
48
adaptations of root hair cells
- hair-like projections with thin cell walls - relatively large numbers of mitochondria
49
adaptations of guard cells
- thicker inner wall

ocr a level biology (9 decks)

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