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biology > D2.1 - cell and nuclear division > Flashcards

D2.1 - cell and nuclear division Flashcards

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1
Q

anucleate

A

without a nucleus

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2
Q

cancer

A

a disease caused when cells divide uncontrollably and spread into surrounding tissues

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3
Q

meristem

A

an area of plant tissue containing undifferentiated cells that can divide rapidly

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4
Q

mutation

A

a change in the base sequence of DNA

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5
Q

mutation

A

a change in the base sequence of DNA

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6
Q

non-sister chromatids

A

chromatids of homologous chromosomes

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7
Q

sister chromatids

A

sisters of the same chromosome, formed by DNA replication

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8
Q

homologous chromosome

A

two chromosomes that contain the same genes at the same loci (ie, they have an identical sequence of genes), but which may contain different alleles

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9
Q

meristem

A

an area of plant tissue that contain undifferentiated cells that divide rapidly

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10
Q

sister chromatid

A

chromatids of the same chromosome, formed by DNA replication

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11
Q

somatic

A

of the body

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12
Q

bivalent

A

homologous chromosomes that are paired up together

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13
Q

proliferation

A

rapid growth or division

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14
Q

proliferation

A

rapid growth or division

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15
Q

cancer

A

a disease caused when cells divide uncontrollably and spread into surrounding tissues

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16
Q

somatic

A

of the body

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17
Q
A
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18
Q

how are the number of chromosomes determined?

A

number of centromeres

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19
Q

gametogenesis

A

processes that form gametes

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20
Q

homologous chromosomes

A

chromosomes that contain the same genes at the same loci but different alleles

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21
Q

how are new cells in living organisms generated?

A

a parent cell (mother cell) divides to produce 2 daughter cells

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22
Q

mitosis

A

nuclear division where a mother cell splits into 2 daughter cells
- involved in asexual reproduction
- maintains the chromosome number and genome of cells, so daughter cells are genetically identical to parent cells

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23
Q

what is mitosis important for?

A
  • growth
  • repair
  • reproduction
  • avoids the production of anucleate cells
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24
Q

cytokinesis

A

splitting of the cytoplasm in a parent cell between daughter cells

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25
Q

how does cytokinesis occur in animal cells?

A

ring of contractile actin and myosin proteins pinches a cell membrane together to form a cleavage furrow which splits the cytoplasm

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26
Q

how does cytokinesis occur in plant cells?

A

vesicles fuse together to assemble sections of the membrane and cell wall to achieve splitting

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27
Q

equal cytokinesis

A

each daughter cell receives half of the components of the parent cell

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28
Q

what is needed for unequal cytokinesis to occur?

A

each daughter cell must receive at least one mitochondrion and one of any other organelle that can only be made by dividing a pre-existing structure

29
Q

what are examples of unequal cytokinesis?

A
  • budding in yeast
  • oogenesis in humans, following meiosis
30
Q

meiosis

A

type of nuclear division where the daughter cells have half the number of chromosomes and creates genetic diversity
- avoids the production of anucleate cells
- involved in sexual reproduction
- part of gametogenesis (generation of new wells that are gametes)

31
Q

what does meiosis reproduce?

A

one diploid nucleus forms four haploid nuclei
4 chromosomes –> 2 chromosomes –> 2 chromosomes
8 chromatids –> 4 chromatids –> 2 chromatids

32
Q

what does haploid and diploid mean?

A

haploid - 2 pairs of homologous chromosomes
diploid - doesn’t have a pair of homologous chromosome

33
Q

why is meiosis needed in sexual life cycles?

A

chromosomes are halved during meiosis so that when gametes undergo fertilisation, the chromosome number doesn’t double in the offspring and the original number of chromosomes is restored

34
Q

why is DNA replication a prerequisite for both mitosis and meiosis?

A
  • after replication, each chromosome consists of two elongated DNA molecules held together at the centromere
  • when these sister chromatids are separated at the anaphase, the chromosome number briefly doubles
  • once telophase and cytokinesis have occured, the original number of chromosomes are restored
35
Q

histones

A

proteins that wrap DNA around themselves to supercoil DNA and condense the chromosomes

36
Q

spindle fibres

A

long strands of microtubules that are produced by the centrosome
- lengthened or shortened by changing the number of microtubules subunits

37
Q

astral microtubules

A

contribute to separating the poles of the cell

38
Q

overlap microtubules

A

connected in pairs by microtubule motor proteins which are pushed towards the poles

39
Q

kinetochore microtubules

A

bind to the centromere of chromosomes with each chromatid attached to the microtubules from each pole, causing the chromatids to move to each pole

40
Q

what is the process of mitosis?

A
  1. prophase - chromosomes condense
  2. metaphase - chromosomes align in the equator
  3. anaphase - homologous chromosomes separate
  4. telaphase - nucleus forms around chromosomes at each pole
41
Q

what is the process of meiosis?

A
42
Q

what happens during prophase in mitosis?

A
  • chromosomes supercoil
  • centrosomes move away to the poles and form spindle fibres
  • nuclear membrane breaks down
43
Q

what happens during metaphase in mitosis?

A
  • spindle fibres grow and attach to centromeres
  • chromosomes move along the equator
44
Q

what happens during anaphase in mitosis?

A
  • spindle fibres contract and separate the cetromeres and sister chromatids, moving to opposite poles
45
Q

what happens during telophase in mitosis?

A
  • nuclear membrane reforms around chromosomes at each pole and form two new nuclei
46
Q

what is the order of the cell cycle?

A
  1. interphase - growth and number of sub-cellular structures double
  2. mitosis - cell division
  3. cytokinesis - cytoplasm splits and moves apart
47
Q

what occurs in meiosis I?

A

homologous chromosomes are separated

48
Q

what occurs in meiosis II?

A

sister chromatids are separated

49
Q

what is the process of meiosis?

A
  • Prophase I
  • Metaphase I
  • Anaphase I
  • Telophase I
  • Prophase II
  • Metaphase II
  • Anaphase II
  • Telophase II
50
Q

what occurs in prophase I?

A
  • homologous chromosomes pair up to form bivalents - there is crossing over between non-sister chromatids, causing an exchange of alleles.
  • chromosomes condense by supercoiling
51
Q

what occurs in metaphase I?

A

pairs of homologous chromosomes move to the equator of the cell, attached to spindle fibres
- orientation of chromosomes before separation is random

52
Q

what occurs in anaphase I?

A
  • homologous chromosomes are pulled apart by spindle fibres
  • centromeres do not divide so the whole centromere and 2 sister chromatids go to opposite poles, halving the chromosome number
53
Q

what occurs in telophase I?

A
  • centromere with 2 sister chromatids arrive at each pole and 2 haploid nuclei are produced
54
Q

what occurs in prophase II?

A

chromosomes re-condense

55
Q

what occurs in metaphase II?

A

single chromosomes move to the equator of the cell, attached to spindle fibres

56
Q

what occurs in anaphase II?

A

sister chromatids separate

57
Q

what occurs in telophase II?

A

4 haploid nuclei are produced, each genetically different

58
Q

what is non-disjunction?

A

an error in meiosis where chromosomes fail to separate correctly

59
Q

when can non-disjunction occur?

A

1) during meiosis 1 - homologous pair of chromosomes do not separate at anaphase I, so an entire bivalent moves to a pole.
- this means that both chromosomes end up in the same nucleus during telophase I and 2 gametes have an extra chromosome while 2 gametes have missing chromosomes
2) during meiosis II - sister chromatids do not separate and both move to 1 pole, so they end up in the same nucleus during telophase II, so out of the 4 gametes produced, 2 will have the normal amount of chromosomes, 1 will have an extra chromosome and 1 will have a missing chromosome

60
Q

what will be caused by the fertilisation of a cell that has an extra chromosome?

A

trisomy - three chromosomes of 1 type

61
Q

what are 2 ways genetic variation occurs within meiosis?

A
  1. Random orientation
  2. Crossing-over
62
Q

what is random orientation?

A

the process by which 2 genes located on different chromosomes are inherited independently of one another

63
Q

what is the impact of random orientation?

A
  • the 2 traits caused by those genes are also inherited independently; there is independent assortment of genes and traits
  • due to the frequency of crossing over, this pattern of inheritance is also seen for genes located far apart on the same chromosome
64
Q

how does random orientation lead to genetic variation?

A
  • random orientation occurs due to homologous chromosomes aligning independently and randomly on the equator during metaphase I, and then the homologues are pulled to seperate poles during anaphase I
  • this means that a random combination of chromosomes (1 from each pair) will end up at each pole.
65
Q

what is crossing over?

A

exchange of alleles between non-sister chromatids, causing a new combination of alleles to occur in chromosomes, gametes and therefore offspring

66
Q

when does crossing over occur?

A

during prophase I, when synapsis brings homolgous chromosomes together to form bivalents

67
Q

how does crossing-over lead to genetic variation?

A
  • chiasmata form, which are points of attachment between non-sister chromatids (chromatids of homologous chromosomes)
    which increases the stability of bivalents
  • the exchange of DNA and alleles between the non-sister chromatids leads to 4 genetically distinct chromatids within the bivalent.
  • at anaphase 1, the homologues are separated to each pole
68
Q

what is the impact of crossing-over?

A

1) at the end of meiosis I, the chromosomes have 2 different chromatids; one has the parental combination of alleles and the other has the recombinant mix of alleles.
2) in meiosis II, these genetically distinct sister chromatids are separated, leading to 4 genetically different chromosomes and 4 genetically different gametes, which have a unique combination of alleles.

biology (28 decks)

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