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Biology > Cell division > Flashcards

Cell division Flashcards

1
Q

What are the phases of cell cycle and outline processes

A

interphase- period of normal functioning, growth and DNA replication in prep for mitotic phase

Mitotic phase- (nucleus and cytoplasm divide), mitosis and cytokinesis=period of cell division

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2
Q

List 3 stages of interphase and outline what happens at each

A

G1= protein synthesis, organelles replicate, cell increases in size

S= synthesis, DNA is replicated in nucleus

G2=cell increases in size, energy stores increase, duplicated DNA checked for errors

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3
Q

List 2 stages of mitotic phase and outline what happens in both

A

Mitosis= nucleus divides
Cytokinesis= cytoplasm divides and 2 cells are produced

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4
Q

Describe significance of G0

A

phase when cell leaves cell cycle temporarily or permanently
- differentiation: cells no longer divide, they carry out their function indefinitely and don’t enter cycle again
- damaged DNA: damaged cells can no longer divide, preventing cancer
- regulates number of cells in tissue

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5
Q

Outline checkpoints role to control cell cycle

A

ensures a cell only divides once reached correct size
DNA replication is error-free
chromosomes are in correct positions during mitosis

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6
Q

3 examples of checkpoints

A

G1
G2
M (spindle assembly checkpoint)

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7
Q

when does G1 checkpoint occur

A

at end of G1 phase before entry to S phase

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8
Q

where does G2 checkpoint occur

A

end of G2 phase before entry to M phase

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9
Q

where does M checkpoint occur

A

during metaphase of mitosis

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10
Q

what does G1 checkpoint check

A

cell size, nutrients, growth factors, DNA damage

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11
Q

what does G2 checkpoint check

A

cell size, DNA replication, DNA damage

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12
Q

what does M checkpoint check

A

if all chromatids are correctly attached to spindle fibres

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13
Q

what happens if G1 checkpoint criteria are satisfied

A

Cell enters S phase and DNA replication begins

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14
Q

what happens if G2 checkpoint criteria are satisfied

A

molecular processes that signal beginning of mitosis are initiated

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15
Q

what happens if M checkpoint criteria are satisfied

A

cell continues with mitosis

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16
Q

what happens if G1 checkpoint criteria are not satisfied

A

cell enters G0

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17
Q

what happens if G2 checkpoint criteria are not satisfied

A

cell pauses G2 to try and repair, if irreparable then cell undergoes apoptosis

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18
Q

what happens if M checkpoint criteria are not satisfied

A

mitosis paused, repair attempted

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19
Q

define mitosis

A

nuclear division stage in mitotic phase of the cell cycle

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20
Q

define chromatids

A

one of two halves of a replicated chromosome

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21
Q

define sister chromatids

A

identical copies formed by DNA replication of a chromosome with both copies joined together by a common centromere

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22
Q

define sister chromatids

A

identical copies formed by DNA replication of a chromosome with both copies joined together by a common centromere

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23
Q

define centromere

A

region which holds 2 chromatids together

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24
Q

define spindle fibres

A

structures made of microtubules that organise chromosomes and pull them part to opposite poles during mitosis

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25
Q

define homologous pairs

A

matching pair of chromosomes, one inherited from each parent

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26
Q

describe how DNA is packaged in a chromosome

A

tightly packed DNA
found only during cell division
DNA not being used for macromolecule synthesis

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27
Q

describe how DNA is packaged in a chromatid

A

unwound DNA
found throughout interphase
DNA is being used for macromolecule synthesis

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28
Q

describe formation of chromosomes

A
  • DNA is wrapped around histone proteins (compact)= chromatin
  • during interphase, chromatin is decondensed
    -during mitosis, chromatin is condensed=chromosomes
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29
Q

list stages of mitosis in order

A

propase
metaphase
anaphase
telophase

30
Q

what happens during prophase

A

-chromatin fibers coil and condense to form chromosomes
-nucleolus disappears
-nuclear membrane breaks down’
-protein microtubules form spindle fibers
-centrioles migrate to opposite poles
-spindle fibers attach to specific areas on centromeres, start moving chromosomes to centre

31
Q

what happens during metaphase

A

chromosomes moved by SF and line up along equator of cell

32
Q

what happens during anaphase

A

-sister chromatids pulled apart to opposite poles by spindle fibres (contract)
-centromeres divide

33
Q

what happens during telophase

A
  • nuclear envelope reforms around each chromatid
    -chromosomes start to uncoil
  • nucleolus is formed
    -cytokinesis begins
34
Q

role of centrioles

A

organise spindle fibers which are attached to them

35
Q

role of spindle fibers

A

pull chromatids to opposite poles and ensure even chromosome distribution between daughter cells

36
Q

describe process of cytokinesis in animal cells

A

-cleavage furrow forms around middle of cell
-plasma membrane pulled inwards by cytoskeleton until close enough to fuse around middle
-two cells are formed as a result

37
Q

describe process of cytokinesis in plant cells

A
  • vesicles from golgi begin to assemble in same place along equator where chromosomes aligned (metaphase plate)
    -vesicles fuse with eachother and cell surface membrane dividing cell in two.
  • new sections of cell wall form along new sections of membrane

cleavage furrow cannot form as plants have cell walls

38
Q

compare animal and plant cytokinesis

A

-animal cells form cleavage furrow but plants don’t (bc they have a cell wall and internal P)
-plant cells use vesicles, animals don’t

39
Q

purpose of mitotic cell division

A
  • ensures that both daughter cells produced when a parent cell divides are genetically identical.
    -necessary when all DC have to be identical
40
Q

list 4 roles of mitosis

A

-growth of organisms
-repair/replacement of tissues
-embryo development
-asexual reproduction

41
Q

what is mitotic index

A

ratio between number of cells in mitosis and total number of cells

41
Q

what is mitotic index

A

ratio between number of cells in mitosis and total number of cells

42
Q

define diploid

A

containing homologous chromosome pairs- two complete sets of chromosomes, one from each parent

43
Q

define haploid

A

containing one chromosome from each homologous pair

44
Q

define gamete

A

haploid sex cells produced by meiosis in organisms that reproduce sexually

45
Q

define zygote

A

initial diploid cell formed when 2 gametes are joined by sexual reproduction
-earliest stage of embryonic development

46
Q

define meiosis

A

nuclear division for the purpose of gamete production
-nucleus divides twice resulting in forming four haploid cells from one diploid cell

47
Q

define reduction division

A

where the chromosome number is halved from diploid to haploid (first meiotic division)

48
Q

role of meiosis in life cycles

A

-production of gametes which allow sexual reproduction
-ensures all organisms produces via sexual reproduction contain the correct number of chromosomes would double with every round of reproduction
-produces genetic variation

49
Q

how does meiosis produce variation

A

-crossing over during prophase 1
- independent assortment of chromosomes in metaphase 1
-independent assortment of chromatids in metaphase 2

50
Q

importance of different allele combinations

A

-this means that different phenotypes will be produced
-this reduces the chances of a population going extinct as it is more likely that some individuals possess advantageous characteristics to help them survive and adapt

51
Q

define homologous chromosomes

A

matching pair of chomosomes, one inherited from each parent

52
Q

define bivalent

A

a pair of homologous chromosomes during crossing over

53
Q

define crossing over

A

exchange of genes between homologous chromosomes, resulting in a mixture of parental characteristics in offspring

54
Q

define chiasmata

A

points at which chromatids break and rejoin

55
Q

define recombinant chromatid

A

chromatid with a combination of DNA from both homologous chromosomes
-formed from crossing over and chiasmata in meiosis

56
Q

state stages of meiosis in order

A

prophase 1
metaphase 1
anaphase 1
telophase 1
prophase 2
metaphase 2
anaphase 2
telophase 2

57
Q

what happens at P1

A

-chromosomes condense
-nuclear envelope disintegrate
-nucleolus disappears
-spindle formation begins
-homologous chromosomes pair up, forming bivalents & crossing over occurs

58
Q

what happens at M1

A

-homologous pairs assemble along metaphase plate
-independent assortment occurs

59
Q

what happens at A1

A

-homologous chromosomes pulled to opposite poles and chromatids stay joined to each other
-entangles sections of DNA on non-sister chromatids that became entangled during crossing over break off and rejoin at chiasmata, resulting in recombinant chromatids

60
Q

what happens at T1

A

-chromosomes assemble at each pole, nuclear membrane reforms
-chromosomes uncoil
-cytokinesis occurs, cell divides into 2
-reduction of chromosome number from diploid to haploid is complete

61
Q

what happens at P2

A

-chromosomes condense and become visible.
-nuclear envelope breaks down, spindle formation begins

62
Q

what happens at M2

A

-individual chromosomes assemble on metaphase plate
-due to crossing over, chromatids are not identical= independent assortment occurs

63
Q

what happens at A2

A

chromatids of individual chromosomes are pulled to opposite poles after division of centromeres.

64
Q

what happens at T2

A

-chromatids assemble at poles, uncoil and form chromatin.
-nuclear envelope reforms, nucleolus is visible again.

65
Q

describe process of crossing over

A

-HC pair up=bivalent
-non-sister chromatids become entangled at points called chiasmata
-they break off and reform, sometimes resulting in the exchange of DNA=recombinant chromatids with diff combinations of alleles and therefore gen variation

66
Q

describe process of random independent assortment

A

-orientation of each HP on metaphase plate is random and independent of any other HP
-maternal/paternal chromosomes can end up with any combination of maternal and paternal chromosomes hence why it produces genetic variation

67
Q

similarities between meiosis and mitosis

A

-begin with 1 diploid parent cell
-end with cytokinesis
-both stages duplicate DNA
-both stages condense DNA
-both require chromosomes to be pulled apart by a centrosome
-both pulled apart by spindle fibres formed from centrosome
-require nuclear membrane to go away

68
Q

differences between meiosis and mitosis

A

-mitosis is used in asexual reproduction and meiosis in sexual
-crossing over occurs in meiosis not mitosis
-cells produced in mitosis are genetically identical, meiosis is gen diff
-mitosis used for growth and repair, meiosis used for genetic diversity through sexual reproduction
-cells divide once in mitosis but twice in meiosis
-2 diploid cells produced in mitosis and 4 haploid in meiosis
-n. chromosomes stays same in mitosis but in meiosis is halved
-mitosis used to create any cell (except gamete), meiosis used only to create sex cells

69
Q

define specialised

A

having particular structure to serve a specific function

70
Q

define differentiated

A

specialised to carry out a very specific funtion

Biology (13 decks)

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