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biology > topic 2.3 - cell cycle & division > Flashcards

topic 2.3 - cell cycle & division Flashcards

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1
Q

what is the cell cycle & its 3 main stages

A
  • cell cycle is a process in which cells divide into two identical daughter cells
  • interphase
  • mitosis
  • cytokinesis
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2
Q

interphase

A
  • interphase - the period between active cell divisions when cells increase size and mass and replicate their DNA
  • new DNA is produced, chromosomes replicate, new proteins, cytoplasm, cell organelles are synthesised
  • ATP production increases at times to provide extra energy needed for cell to divide

~ 90% of the cell cycle

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3
Q

G1, S, G2

A
  • G1 - time between end of previous round of mitotic cell division and start of chromosome duplication.
    grows and develops
    very short
  • S - stage where chromosomes replicate and become double stranded chromatids.
    CHROMATIDS - one strand of the replicated chromosomes pair that’s joined to other chromatid at the centromere.
  • G2 - time that organelles + materials needed for cell division are synthesised - need 2 for everything before cell divides.
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4
Q

prophase

A
  • chromosomes coil and condense - can take up stain and become visible
  • each chromosome consists of 2 chromatids joined at centromere
  • nuclear envelope breaks down and centrioles move to opposite poles and pull apart to from spindle fibres between them
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5
Q

metaphase

A
  • chromosomes line up along the equator
  • each centromere pair attaches to the spindle fibres
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6
Q

anaphase

A
  • the centromere splits, separating the 2 chromatids into two separate ‘chromosomes’
  • the chromatids from each old pair are drawn to opposite poles of the cell
  • they cannot move - spindle moves them
  • contraction of overlapping spindles cause them to move to opposite ends
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7
Q

telophase

A
  • spindle fibres break down and nuclear envelopes form around the 2 sets of chromosomes
  • chromosomes uncoil & become less dense (long + thin) & harder to see
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8
Q

cytokinesis

A
  • happens after mitosis; division of cytoplasm
  • plasma membrane folds inwards
  • cell splits into 2 new identical diploid daughter cells
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9
Q

what are cyclins

A

small proteins that build up during interphase and are involved in the control of the cell cycle by their attachment to cyclin-depending kinases

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10
Q

what are cyclin-depending kinases - CDK’s

A
  • cyclin-dependent Kinases (CDKs) are enzymes involved in the control of the cell cycle
  • cyclin attach to CDKs and this cyclin/CDKs complex adds phosphate to other proteins, changing their shape and bringing about the next stage in the cycle
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11
Q

what are the roles of mitosis

A
  • growth
  • repair
  • reproduction
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12
Q

what are some measure of growth?

A
  • height
  • head circumference
  • mass (dry mass for fungi/plants not animals as they’ll die with no water)
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13
Q

continuous growth

A

rapid period of growth until maturity is reached - growth slows and may stop.
(land animals, marine animals grow for life)

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14
Q

discontinuous growth

A
  • grow, stop, repeat.
  • insects grow in series of steps/bursts.
  • they shed one exoskeleton whilst new one is soft they expand their body by taking in air and water = ‘grow’
  • then new skeleton hardens & water is released & there’s room for tissues to increase in mass/size
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15
Q

asexual reproduction

A
  • asexual reproduction involves only one parent
  • results in genetically identical clones to each other & parent
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16
Q

advantages vs disadvantages of asexual reproduction

A

ADV:
- don’t need to find mate so it’s easier
- gives rise to large numbers of offspring rapidly
- can replicate desired traits

DISADV:
- no variation
- if conditions change/disease comes = can cause total destruction to entire species

17
Q

asexual reproduction methods

A
  • binary fission
  • sporulation
  • regeneration
  • Budding
  • Vegetative propagation
18
Q

binary fission

A
  • mitosis followed by splitting of an individual
  • 2 new individuals formed.
  • most common in bacteria
19
Q

sporulation

A
  • production of spores through mitosis
  • spores land on suitable substrate
  • spores grow into new organism
  • spores are well suited to survive in adverse conditions
  • most common in fungi and plants such as mosses
20
Q

regenration

A
  • organisms replace lost body parts by producing new cells by mitosis
  • lizard’s tails
21
Q

fragmentation

A
  • can reproduce themselves asexually through fragments of their original body.
  • starfish
22
Q

budding

A
  • organisms produce a growth of ‘bud’ from their bodies through mitosis
  • the bud eventually breaks of & forms a new independent organism genetically identical to parent.
  • yeast / hydra animal
23
Q

vegetative propogation

A
  • when parts of a plant extend out under soil (propagate from stem/leaf/root/bud) and give rise to a new plant
  • e.g. farmers use it with plants/strawberries
24
Q

what are gametes and where are they produced?

A
  • Gametes are sex cells
  • haploid (23 chromosomes)
  • contain half the number of chromosomes as the rest of the cells which make up our body
  • when two gametes fuse during sexual reproduction, the fertilised egg ( zygote) contains the full number of chromosomes
  • it is diploid = 46
25
Q

difference between egg & sperm

A
  • sperm = many, mini, mobile (can move)
  • egg = few, fat/big, fixed/can’t move.
26
Q

meiosis 1

A
  • Prophase 1 - chromosomes condense with 2 chromatids joined at centromere; (crossing over occurs)
  • Metaphase 1 - spindle fibres form and pair of chromosomes line up at equator/middle plate.
    (independent assortment occurs)
  • Anaphase 1 - centromeres DO NOT divide. one chromosome from each homologous pair move to opposite ends of cell = chromosome number in each cell will be half the original due to this.
  • Telophase 1 - nuclear membrane re-forms and the cells begin to divide
27
Q

meiosis 2

A
  • Metaphase 2 - new spindles formed and chromosomes line up in metaphase plate/equator
  • Anaphase 2 - centromere NOW divides and chromatids split & go to opposite ends of cell.
  • Telophase 2 - nuclear envelope re-forms & cytokinesis occurs. results in 4 genetically different haploid daughter cells ( half number chromosomes as original diploid cell)
  • haploid gametes formed
28
Q

how does meiosis bring variation?
1. independent/random assortment

A
  • chromosomes from parents are distributed to gametes completely randomly
  • so new gamete can have nay amount of chromosomes from either parent
  • this guarantees great variety in gametes
29
Q

how does meiosis bring variation?
2. crossing over/recombination

A
  • a large enzyme ‘cuts & joins’ bits of maternal and paternal chromatids together
  • the chiasmata (points where chromatids break) are important in 2 ways:
    1. exchange of genetic material = genetic variation
    2. errors in the process leads to mutations - introduces new combinations into the genetic make-up of a species.
30
Q

what is a chromosome mutation?

A
  • changes to the number or structure of chromosomes during meiosis
31
Q

types of chromosome mutations

A
  1. translocation
  2. deletion
  3. inversion
  4. non disjunction
32
Q

mutation through translocation

A
  • where a part of one chromosome breaks off and reattaches to another completely different chromosome
  • can be balanced or unbalanced
  • balanced -a piece is swapped between 2 different chromosomes
  • unbalanced - one chromosome loses a part and doesn’t get another one in exchange whilst the other chromosome gains it.
33
Q

mutations through deletion

A

deletion - a section of chromosome is removed resulting in loss of a large number of genes

34
Q

mutations through insertion

A

inversion - a part of a chromosome flips its orientation with respect to the rest of the chromosome

35
Q

non disjunction

A
  • causes abnormal number chromosomes in all the cells
  • 3 chromosome 21 - results in Down’s syndrome
36
Q

why do we need meiosis

A
  • results in genetic variation
  • because crossing over occurs and there is independent assortment
  • it produces new combinations of alleles
  • genetic variation allows organism to adapt to environmental changes
37
Q

describe the process of crossing over

A
  • homologous chromosomes line up
  • chiasmata forms
  • chromosomes break
  • genetic information exchanged between chromatids
38
Q

what is an allele

A

different version of a gene

39
Q

how does meiosis result in genetic variation

A
  • results in recombination of alleles
  • chromosomes cross over
  • independent assortment occurs

biology (29 decks)

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