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Biology > 2.1.6 Cell Division , Cell Diversity And Cellular Organisation > Flashcards

2.1.6 Cell Division , Cell Diversity And Cellular Organisation Flashcards

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1
Q

What are the stages of the cell cycle in order?

A
  • interphase (G1, S, G2,)
  • mitotic phase (mitosis and cytokinesis)
  • (G0) leave cell cyle to enter G0
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2
Q

What happens at each stage (3) of interphase?

A

3 stages of interphase:
- G1: organelles replicate, cell grows, new proteins made
- Synthesis: cell replicates its DNA (in nucleus)
- G2: cell keeps growing, energy stores (ATP) increased, replicated DNA checked for errors

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3
Q

What happens during mitosis?

A
  • division of the nucleus
  • (prophase, metaphase, anaphase, telophase)
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4
Q

What happens during cytokinesis?

A

division of the cytoplasm producing 2 genetically identical daughter cells.

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5
Q

What happens during G0?

A
  • cell leaves cycle and cell division stopped
  • can undergo differentiation and specialisation
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6
Q

What are the 2 stages of the mitotic phase?

A
  • mitosis (PMAT)
  • cytokinesis - division of cytoplasm
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7
Q

What are the role of checkpoints to control the cell cycle?

A
  • checkpoints monitor and check if each phase of cell cycle has been accurately completed before moving onto the next
  • checkpoibnts insure each division is successful in producing 2 genetically identical daughter cells.
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8
Q

What are the 3 checkpoints in the cell cycle?

A
  • G1 checkpoint
  • G2 checkpoint
  • metaphase checkpoint
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9
Q

Where does each checkpoint occur?

A

G1: - end of G1
G2: - end of G2
metaphase/spindle assembly checkpoint: end of metaphase

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10
Q

What is checked at each checkpoint?

A
  • G1 checks: cell size, nutrients growth factors, DNA damage
  • G2 checks: cell size, DNA replication, DNA damage
  • spindle assembly checkpoint/ metaphase : chromosome attatchement to spindle
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11
Q

What is the link between cell-cycle regulation and cancer?
(s+c)

A
  • cancer caused by unregulated division of cells
  • occurs when proteins regulating cell cycle at checkpoints don’t function properly
  • division is uncontrolled and tumours form
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12
Q

Define mitosis

A
  • the nuclear division (division of nucleus) stage of the mitotic phase of the cell cycle
  • at the end of mitosis there are 2 genetically identical daughter cells (exact copy of parent cell DNA)
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13
Q

Define chromosome

A
  • structure of condensed and coiled DNA made up of two seperate chromatin strands which are joined by a centromere
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14
Q

Define chromatid

A

the two seperate strands which a chromosome divides into during cell division

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15
Q

Define sister chromatids

A

2 chromatid strands on the same chromosome

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16
Q

Define centromere

A

the region at which 2 chromatids are held together

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17
Q

Define centrioles

A
  • component of the cytoskeleton of most eukaryotic cells
  • tiny bundles of protein which move to opposite ends of the cell during prophase
  • help form spindle
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18
Q

Define spindle fibres

A
  • a network of filaments that form a miotic spindle
  • made up of protein microtubules
  • attatch to the centromeres and responsable in moving and separating chromosomes
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19
Q

Define homologous pairs

A
  • matching pair of chromosomes, one inherited from each parent
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20
Q

How is DNA packaged in a chromosome?

A
  • double stranded DNA loops around histones forming the nucleosome
  • DNA further packaged by forming coils of nucleosomes called chromatin fibres
  • these fibres are condensed into chromosomes during mitosis/cell division process
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21
Q

Draw, and annotate, a diagram for each stage of mitosis to show the events occurring at each stage

A
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22
Q

What are the roles of centrioles and spindle fibres in mitosis?

A
  • centrioles make/form the spindle fibres
  • spindle fibres attatch to the centromeres and seperate the chromatids, drawing them to each pole of the cell to form the 2 new nuclei
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23
Q

describe the process of centrioles making the spindle fibres

A

cetrioles move to opposite poles of the cell and start coordinating the formation of spindle fibres (they come out of the centrioles)
spindle fibres attatch to the centromeres

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24
Q

What is the process of cytokinesis in animal cells?

A

cytokinesis - division of the cell into 2 separate cells, begins during telophase
1- cleavage furrow forms around the middle of the cell
2- cytoskeleton pulls cell surface membrane inwards until close enough the fuse to form 2 seperate cells

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25
Q

What is the process of cytokinesis in plant cells?

A

-(have cell wall so not possible for cleavage furrow)
1- vesicles from golgi apparatus line up along centre of cell
2- vesicles fuse together and with cell surface membrane of the cell to form new cell surface membrane down the middle
3- new sections of cell wall then form along the new surface membrane

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26
Q

Compare the process of cytokinesis in animal cells and plant cells?

A
  • in animal cells a cleavage furrow forms but in plant cells this is not possible as the have a cell wall
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27
Q

Is mitosis necessary for sexual or assexual reproduction?

A

asexual reprodution

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28
Q

What happens during prophase in mitosis?

A

Prophase:
- chromosomes condense (become shorter and fatter and visible)
- the nucleolus disappears and nuclear envelope breaks down
- centrioles move to opposite poles of cell and form spidle fibres
- spindle fibres attatch to centromeres of each chromosome

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29
Q

What happens during metaphase (mitosis)?

A

Metaphase:
- chromosomes moved by spindle fibres
- and lined up at the equator of the cell
(metaphase checkpoint- cell checks that all chromosomes are attatched to the spindle)

30
Q

What happens during anaphase (mitosis)?

A

anaphase:
- centromeres (holding pair of chromatids) divide
- spindle fibres shorten/contract pulling chromatids to opposite poles of the cell
- (centromere pulled first)

31
Q

What happens during telophase (mitosis)?

A

telophase:
- chromatids have reached opposite poles
- chromatids uncoil and long/thin again - now chromosomes
- spindle fibres break down
- nucelar envelope forms around each now group of chromosomes
- 2 nuclei now
(cytokinesis starts and separates cell into 2)

32
Q

Explain the root tip squash practical to view different stages of the cell cycle.

A

1) treat the tips of growing roots in HCL
2) cut small thin section from the meristem
3) create a thin layer of cells by squashing tissue onto a microscope slide
4) stain the tissue (toluidine blue)
5) cover with a cover slip

33
Q

What is the purpose of mitosis?

A

to create more gentically identical cells

34
Q

What are 4 roles of mitotic cell division?

A
  • growth, repair, replace, asexual reproduction
35
Q

Define diploid

A

a cell with 2n chromosomes (2 copies of each chromosome, one from each parent)

36
Q

Define haploid

A

a cell with n chromosomes (one copy of each chromosome)

37
Q

Define gamete

A

haploid sex cell

38
Q

Define gamete

A

haploid sex cell

39
Q

Define zygote

A
  • fertilised egg cell
    -cell produced when haploid egg cell (gamete) is fertilised by haploid sperm cell (gamete)
40
Q

Define meiosis

A
  • nuclear division that results in production of haploid (gametes) nuclei from a diploid nucleus
    (cell division that halves the original genetic material in cells to make haploid cells for sexual reproduction)
41
Q

Define reduction division

A

any form of nuclear division where the chromosome number is reduced

42
Q

Explain the role of meiosis in life cycles

A
  • needed for sexual reproduction
  • it halves the number of chromosomes so the diploid number of chromosomes is restored at fertilisation
  • produces genetic variation in offspring
43
Q

What are 2 ways in which meiosis produces variation?

A
  • independant assortment
  • crossing over
44
Q

What is the importance of the creation of different allele combinations in populations?

A
  • different allele combinations = genetic variation
  • genetic variation is important in populations
  • less vulnerability to disease/change in conditions as some more suited to new environment
45
Q

Define homologous chromosomes

A
  • matching pair of chromosomes, one inherited from each parent (same size, same genes)
46
Q

Define bivalent

A

name for 2 homologous chromosomes that have paired up
(in prophase I of meiosis)

47
Q

Define crossing over

A

the exchange of a part of a chromosome between chromatids of homologous pairs (happens at chiasmata)

48
Q

Define chiasmata

A
  • point of breakage
  • sections of DNA that became entangled during crossing over, break and rejoin - point that they break is chiasmata
49
Q

Define recombinant chromatid

A
  • chromatids with a combination of DNA from both homologous chromosomes
  • formed by crossing over and chiasmata in meiosis
50
Q

Define random independent assortment

A
  • which daughter cell a chromosome ends up in after meiosis I
  • or a chromatid ends up in after meiosis II is random and independent of the fate of chromsomes from other homologous pairs
51
Q

Describe the 2 stages of meiosis
snaprevise for diagrams

A
  • Meiosis I - pairs of homologous chromosomes separated into 2 cells
  • each intermediate cell contails 1 full set of chromosomes instead of 2, so haploid
  • Meiosis II - same mechanism as mitosisi but fewer chromosomes
  • pairs of chromatids in 2 daughter cells separated forming 2 more cells
  • 4 haploid cell in total
52
Q

What are the stages of meiosis in order

A

interphase - PMAT I, cytokinesis I , PMAT II, cytokinesis II

53
Q

What happens during prophase I ?

A

Prophase I:
- chromosomes condense (shorter+fatter)
- nuclear envelope breaks down
- centrioles move to opposite poles forming spindle fibres
- homologous chromosomes pair up (1+1, 2+2 etc) forming bivalents
- crossing over occurs

54
Q

What happens during metaphse I ?

A

Metaphase I:
- homologous pairs line up at equator of cell
- attatch to spindle fibres by their centromeres
(independant assortment as maternal/paternal chromosomes randomly get pulled to each pole)

55
Q

What happens during Anaphase I ?

A

Anaphase I:
- spindles contract
- homologous pairs pulled apart (1 chromosome to each end of cell)

56
Q

What happens during Telophase I ?

A

Telophase I:
- nuclear envelope forms around each group of chromosomes
- spindle fibres broken down
- chromosomes uncoil
- cell undergoes cytokinesis

57
Q

How many cells are there at the end of meiosis I ?

A

2 haploid cells

58
Q

What happens during Prophase II ?

A

Prophase II:
- chromosomes condense (shorter+fatter+visible)
- nuclear envelope breaks down
- centrioles move to opposite poles forming spindle fibres

59
Q

What happens during Metaphase II ?

A

Metaphase II:
- homologous pairs of chromosomes assemble along the equator of the cell
- crossing over (chromatids not identical anymore) so independent assortment again bc

60
Q

What happens during Anaphase II ?

A

Anaphase II:
- centrioles divide and spindle fibres contract
- chromatids of individual chromsomes pulled to opposite poles

61
Q

What happens during Telophase II ?

A

Telophase II:
- chromatids have reached opposite poles in cell
- chromotids uncoil and long again - become chromosomes
- nuclear envelope reforms and nucleolus visible again
- cytokinesis happens = 4 haploid daughter cells (genetically different)

62
Q

How many cells are there at the end of meiosis II ?

A

4 haploid daughter cells
- haploid bc of reduction division
- genetically different from each other and from parent cell bc of crossing over and independant assortment

63
Q

Describe the process of crossing over

A
  • homologous pairs of chromosomes come together and pair up
  • chromatids become entangled/twist over at the chiasmata
  • sections of chromatids break off and are exchanged
  • now have a different combination of alleles
64
Q

During which stage of meiosis does crossing over occur?

A

Prophase I of meiosis I

65
Q

How does crossing over produce genetic variation?

A
  • after crossing over chromatids no longer contain just maternal or paternal DNA
  • so each of the 4 daughter cells are different (contain chromatids with different alleles) and there are infinite possibilities for different combinations of DNA
66
Q

Define allele

A

different versions of the same gene

67
Q

Describe the process of random independent assortment

A
  • when bivalents (2 paired up homologous chromosomes) line up in meiosis I/ when chromosomes line up in meiosis II
  • it is random which chromosome goes to which pole of the cell
  • so random which chromosome from each pair ends up in which daughter cell
68
Q

How does independent assortment produces genetic variation?

A
  • the pole that the maternal or paternal homologous chromsomes face is due to random assortment and can result in many different combinations of alleles on either side of equator
  • produces different daughter cells
69
Q

Explain (given the chromosome number of the species)
How to calculate the total number of possible genetically different gametes that could be produced through independent assortment only

A

the number of chromosomes squared

70
Q

When in meiosis does independent assortment occur?

A

metaphase I

71
Q

Compare meiosis I, meiosis II, mitosis
paper flashcard

A
72
Q

compare meiosis and mitosis
paper flashcard

A

Biology (32 decks)

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