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IB biology > topic 1.6- cell division > Flashcards

topic 1.6- cell division Flashcards

1
Q

define mitosis

A

the division of the nucleus into two genetically identical daughter nuclei

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2
Q

what must happen before mitosis can occur?

A

all of the DNA in the nucleus must be replicated

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3
Q

when is the DNA in the nucleus replicated

A

during interphase

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4
Q

what is interphase

A

the period before mitosis

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5
Q

what happens during interphase?

A

each chromosome is converted from a single DNA molecule into two identical DNA molecules (chromatids)

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6
Q

what are the functions of mitosis?

A
  • embryonic development
  • growth
  • tissue repair
  • asexual reproduction
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7
Q

state the 4 phases of mitosis

A
  1. prophase
  2. metaphase
  3. anaphase
  4. telophase
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8
Q

mitosis is a ——– process

A

continuous

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9
Q

interphase is a…

A

very active phase in the life of the cell when many metabolic reactions occur

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10
Q

what only occurs during interphase?

A

DNA replication in the nucleus and protein synthesis in the cytoplasm

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11
Q

why does the no of mitochondria/chloroplasts in the cytoplasm increase during interphase?

A

due to the growth and division of these organelles

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12
Q

what do plants also do during interphase?

A

they synthesise cellulose and use vesicles to add it to their cell walls

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13
Q

what 3 phases does interphase consist of?

A
  • G1 phase
  • S phase
  • G2 phase
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14
Q

G1 phase

A

cell grows physically larger and copies organelles/cellular components except the chromosomes

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15
Q

S phase

A

cell replicates all genetic material in its nucleus

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16
Q

G2 phase

A

cell grows more, makes proteins and organelles, and begins to reorganize its contents in preparation for mitosis

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17
Q

what happens to cells that are never going to divide?

A

they enter a phase called G0

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18
Q

how do chromosomes condense

A

by supercoiling during mitosis

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19
Q

what makes up each chromosome during mitosis?

A

a chromatid

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20
Q

how does condensation occur for chromosomes?

A

by repeatedly coiling the DNA molecule to make the chromosome shorter and wider

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21
Q

what is involved in supercoiling?

A

histones (proteins) associated with DNA and enzymes

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22
Q

prophase

A
  • chromosomes become shorter and fatter by supercoiling
  • nucleolus breaks down
  • microtubules grow from MTOCs to form spindle-shaped array that links poles of the cell
  • end; nuclear membrane breaks down
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23
Q

function of the nucleolus

A

area inside the nucleus of a cell that is made up of RNA and proteins and is where ribosomes are made.

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24
Q

metaphase

A
  • microtubules continue to grow and attach to the centromeres on each chromosome
  • microtubules put under tension to test whether attachment is correct (by shortening of the microtubules at the centromere)
  • attachment=correct, microtubules remain on equator of cell
25
Q

what allows the chromatids of a chromosome to attach to microtubules?

A

the two attachment points on opposite sides of each centromere

26
Q

anaphase

A
  • each centromere divides, allowing the pairs of sister chromatids to separate
  • spindle microtubules pull them rapidly towards the poles of the cell
27
Q

telophase

A
  • at each pole the chromosomes are pulled into a tight group by the MTOC and a nuclear membrane reforms around them
  • chromosomes uncoil and nucleolus is formed
28
Q

telomere

A

structures found at the ends of chromosomes. They cap and protect the end of a chromosome

29
Q

centromere

A

links a pair of sister chromatids together during cell division.

30
Q

equation for mitotic index

A

no of cells in mitosis/total no of cells

31
Q

MTOC

A

microtubule-organizing center; a structure found in eukaryotic cells from which microtubules emerge.

32
Q

when does cytokinesis occur

A

after mitosis

33
Q

what is cytokinesis

A

process of cell division

34
Q

describe cytokinesis in plants

A
  • vesicles are moved to the equator, where they fuse to form tubular structures
  • these merge into two layers of membrane across the whole of the equator
35
Q

how are cell walls formed after mitosis?

A
  • pectins and other substances brought by vesicles and deposited by exocytosis between the two new membranes, forming the middle lamella that links new cell walls.
  • both dcs then bring cellulose to the equator and deposit it adjacent to the middle lamella via exocytosis. this forms a cell wall adjacent to the equator
36
Q

describe cytokinesis in animal cells

A
  1. cleavage furrow formed (plasma membrane pulled inwards around equator).
    - this is accomplished by using a ring of contractile protein (actin and myosin)
  2. when cleavage furrow reaches centre, the cell is pinched apart into 2 cells
37
Q

what are cyclins involved in?

A

the control of the cell cycle

38
Q

description/functions of cyclins

A

proteins:
- control the cell cycle and ensure that cells divide only when new cells are needed

39
Q

how do cyclins work

A
  • bind to enzymes called cyclin-dependent kinases, causing them to become active and attach phosphate groups to other proteins in the cell
  • this triggers the other proteins to become active and carry out tasks specific to one of the cell cycle phases
40
Q

cyclin D

A

triggers cells to move from G0 to G1 and from G1 to S

41
Q

cyclin E

A

prepares cell for DNA replication in the S phase

42
Q

cyclin A

A

actives DNA replication inside the nucleus in the S phase

43
Q

cyclin B

A

promotes the assembly of the mitotic spindle and other tasks in the cytoplasm to prepare for mitosis

44
Q

when will cyclin levels peak

A

when their target protein is required for function

45
Q

state three things involved in the formation of primary and secondary tumours

A
  • mutagens
  • oncogenes
  • metastasis
46
Q

what are tumours

A

abnormal groups of cells that develop at any stage of life in any part of the body

47
Q

when are tumours benign

A

when the cells adhere to each other and do not invade nearby tissues or move to other parts of the body

48
Q

when are tumours malignant

A

when the cells become detached and move elsewhere in the body and develop secondary tutors

49
Q

what are cancers?

A

diseases due to malignant tumours

50
Q

what are carcinomas

A

malignant tumours

51
Q

define a mutagen

A

an agent that changes the genetic material of an organism (either acts on the DNA or the replicative machinery)

52
Q

describe the 3 types of mutagens

A
  • Physical – Sources of radiation including X-rays (ionising), ultraviolet (UV) light and radioactive decay
  • Chemical – DNA interacting substances including reactive oxygen species (ROS) and metals (e.g. arsenic)
  • Biological – Viruses, certain bacteria and mobile genetic elements (transposons)
53
Q

what are carcinogens

A

Mutagens that lead to the formation of cancer

54
Q

define a mutation

A

random changes to the base sequences of genes

55
Q

most genes ——- if they mutate

A

do not cause cancer

56
Q

what are oncogenes

A

genes that become cancer-causing after mutating

57
Q

why are oncogenes cancer-causing

A

in a normal cell, oncogenes are involved in the control of the cell cycle and cell division, so mutations in them will result in uncontrolled cell division = tumour formation

58
Q

metastasis

A

the movement of cells from a primary tumour to set up secondary tumours in other parts of the body

59
Q

smoking and cancer

A

there is a positive correlation between smoking and incidence of cancer;
- cancer of mouth, pharynx, larynx and lungs
- esophagus, stomach, kidney, bladder, pancreas cervix
- Cigarette smoke contains over 4,000 chemical compounds, over 60 of which are known to be carcinogenic

IB biology (60 decks)

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