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Biology > 1.6 cell division > Flashcards

1.6 cell division Flashcards

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1
Q

what does diploid mean

A

2 sets of chromosomes

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2
Q

haploid

A

1 set of chromosones

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3
Q

gametes

A

sex cells

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4
Q

what are chromosomes

A

long sections of DNA

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5
Q

what are chromosomes made up of

A

2 parts that are called chromatids

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6
Q

what are chromatids joined by

A

centromere

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7
Q

at what point do chromosomes become visible

A

at the onset of cell division

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8
Q

how many chromosomes do humans have

A

46
23 pairs of homologous chromosomes

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9
Q

what does mitosis produce

A

two daughter cells that are genetically identical to the parent cell

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10
Q

what is in the life cycle of somatic cells

A

-interphase
-mitosis
- cytokinesis

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11
Q

describe interphase

A

DNA of each chromosome is replicated (copies are called sister chromatids held together at the centromere)
organelles and centrioles replicated
proteins made and the cell carries out its function

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12
Q

4 phases of mitosis

A

prophase
metaphase
anaphase
telophase

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13
Q

explain prophase

A

-replicated chromosomes supercoil/ condense (get shorter/ thicker)
-they are then visible under the microscope
-the nuclear envelope breaks down and disappears
- centrioles divide and move to opposite poles

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14
Q

explain metaphase

A

chromosomes move to the middle of the cell and attaches to the spindle thread (made by the centrioles) by it’s centromere

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15
Q

explain anaphase

A

the spindle fibres shorten/contract pulling the sister chromatids towards the poles (by their centromeres)
-replicated sister chromatids are separated when the centromere holding them together split

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16
Q

explain telophase

A
  • a new nuclear envelope forms around each set
  • spindle fibres break down and disappear
  • chromosomes uncoil (no longer visible)
  • in this phase the cell has 2 nuclei
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17
Q

where does cytokinesis happen in yeast

A

called budding

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17
Q

what is interphase split into

A

Growth phase 1
Growth phase 2
synthesis

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17
Q

where does cytokinesis happen in animals

A

the centre of the cell, the cytoplasm splits to form a cleavage furrow

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18
Q

what happens during cytokinesis

A

cell splits to form 2 new cells
each cell has a full set of chromosomes identical to parent cell
spliting is called cytokinesis

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18
Q

where does cytokinesis happen in plant cells

A

a cell plate made of cellulose is formed at the centre of the cell

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19
Q

what happens during growth phase 1

A

cytokinesis and organelle replication

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20
Q

growth phase 2?

A

DNA replication

21
Q

synthesis

A

where organelles are made and cells carries out their functiosn

22
Q

where does mitosis happen

A

in animal cells it happens in all body cells
in plant cells mitosis only happens in the tips of the roots and the shoots, these are called meristem cells

23
Q

what can unrestricted cell division lead to

A

lead to a cancerous growth

24
Q

what is the length of a cell cycle controlled by

A

enzymes

25
Q

what is the enzyme production controlled by

A

genes, so if the genes are damaged, the cells fail to divide, or divide at the wrong time, divide too much

26
Q

what are tumour supressor genes

A

they’re genes that make the enzymes to prevent it

27
Q

how can some genes cause cancer

A

if they have mutated or if the cell is infected by a virus (HPV) these are called oncongenes

28
Q

how is the mitotic index calculated

A

number of actively dividing cells/
total number of cells x100

29
Q

significance of mitosis

A

growth of an organism
repair of tissues (produce genetically identical daughter cells)
asexual reproduction ( bacteria, fungi, strawberries)

30
Q

explain how the amount of DNA varies during the cell cycle

A

during interphase the amount of DNA is 1x then during DNA replication it doubles to 2x
during PMAT DNA stays at 2x
and then during cytokinesis it goes back to 1x

31
Q

describe meiosis

A

2 cell divisions
one diploid parent cells divide to form four haploid daughter cells that are genetically different to the parent cells

32
Q

what happens in (prophase) meiosis one that’s the same as mitosis

A

condensed chromosomes
nuclear envelope breaks down centrioles divide and move to opposite poles

33
Q

what happens in prophase in meiosis 1 that is different to what happens in mitosis

A

once chromosome from the mum and one from the dad come together in homologous pairs, each are called bivalents
crossing over happens

34
Q

explain crossing over

A

chromosomes pair up, shorten and twist around eachother causing tension. sections of a chromatic may break off and exchange with sections of another chromatid

35
Q

what is the section called where they break off during crossing over

A

chiasmata

36
Q

what happens in metaphase in meiosis 1 that is the same as in mitosis

A

chromosomes move to the middle of the cell (equator) and becomes attached to a spindle thread (made by the centrioles) by its centromere

37
Q

what is the extra thing that happens in metaphase in meiosis 1

A

bivalents arrange themselves at the equator. they lie randomly

38
Q

what is it called when bivalents lie randomly

A

independent assortment

39
Q

what happens in anaphase in meiosis 1

A

the chromosomes of the bivalents separate as the spindle fibres shorten
each like receives a random arrangement of chromosomes
same as mitosis but NO SPLITTING OF CENTROMERE

40
Q

what happened in telephone 1 in meiosis 1

A

the nuclear membrane might reform and the chromosomes uncoil (can no longer see them under a microscope)
Cytokinesis happens

41
Q

what is the purpose of meiosis 1

A

variation

42
Q

purpose of meiosis 11

A

dividing

43
Q

sources of variation
(4)

A

-crossing over and recombination
-independent segregation of chromosomes
- random fertilisation of gameted
- random mating between organisms of the species

44
Q

when does crossing over and recombination happen

A

meiosis 1
prophase 1

45
Q

explain crossing over and recombination

A
  • chromosomes pair up, shorten and twist around eachother causing tension
  • sections of chromatid may break off and exchange with sections of another chromatid
46
Q

explain independent segregation of chromosomes and when does it happen

A

metaphase 1 - pairs of homologous chromosomes at the equator
they arrange themselves in random order

47
Q

explain random fertilisation of gametes

A

during fertilisation, any male gamete can join with any female gamete
thousands of new genetic combinations are possible

48
Q

significance of meiosis

A

sexual reproduction
genetic variation

49
Q

difference in mitosis between plant an animal cells

A

animal- it happens in all body cells
plant- happens only in the tips of the roots and the shoots which are called the meristem cells

50
Q

difference in meiosis in animal and plant cells

A

animal- happens in the gametes (sperm and egg)
plant- meiosis happens in pollen and the egg

51
Q

difference in cytokinesis in plant and animal cells

A

animal- splitting happens in the centre of the cell to form a cleavage furrow
plant- a cell plate ( of cellulose) is formed at the centre of the cell

52
Q

another difference in cell division between plant and animal cells

A

plant cells don’t have centrioles, still make spindle fibres
however animals cells do have them

53
Q

differences between meiosis and mitosis

A

mitosis- growth and repai
meiosis- sexual reproduction
mitosis- one cell division
meiosos- 2 cell divisions
mitosis- cell replication
meiosis- genetic variation
mitosis- diploid cells
meiosis- haploid cells
mitosis- produces genetically identical daughter cells
meiosis- produces genetically different daughter cells
mitosis- in body cells to make body cells
meiosis- reproductive organs to make gametes
mitosis - 2 daughter cells
meiosis - 4 daughter cells

Biology (12 decks)

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