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Biology > 1.6 cell division > Flashcards

1.6 cell division Flashcards

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
where does mitosis happen
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
what can unrestricted cell division lead to
lead to a cancerous growth
24
what is the length of a cell cycle controlled by
enzymes
25
what is the enzyme production controlled by
genes, so if the genes are damaged, the cells fail to divide, or divide at the wrong time, divide too much
26
what are tumour supressor genes
they're genes that make the enzymes to prevent it
27
how can some genes cause cancer
if they have mutated or if the cell is infected by a virus (HPV) these are called oncongenes
28
how is the mitotic index calculated
number of actively dividing cells/ total number of cells x100
29
significance of mitosis
growth of an organism repair of tissues (produce genetically identical daughter cells) asexual reproduction ( bacteria, fungi, strawberries)
30
explain how the amount of DNA varies during the cell cycle
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
describe meiosis
2 cell divisions one diploid parent cells divide to form four haploid daughter cells that are genetically different to the parent cells
32
what happens in (prophase) meiosis one that's the same as mitosis
condensed chromosomes nuclear envelope breaks down centrioles divide and move to opposite poles
33
what happens in prophase in meiosis 1 that is different to what happens in mitosis
once chromosome from the mum and one from the dad come together in homologous pairs, each are called bivalents crossing over happens
34
explain crossing over
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
what is the section called where they break off during crossing over
chiasmata
36
what happens in metaphase in meiosis 1 that is the same as in mitosis
chromosomes move to the middle of the cell (equator) and becomes attached to a spindle thread (made by the centrioles) by its centromere
37
what is the extra thing that happens in metaphase in meiosis 1
bivalents arrange themselves at the equator. they lie randomly
38
what is it called when bivalents lie randomly
independent assortment
39
what happens in anaphase in meiosis 1
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
what happened in telephone 1 in meiosis 1
the nuclear membrane might reform and the chromosomes uncoil (can no longer see them under a microscope) Cytokinesis happens
41
what is the purpose of meiosis 1
variation
42
purpose of meiosis 11
dividing
43
sources of variation (4)
-crossing over and recombination -independent segregation of chromosomes - random fertilisation of gameted - random mating between organisms of the species
44
when does crossing over and recombination happen
meiosis 1 prophase 1
45
explain crossing over and recombination
- chromosomes pair up, shorten and twist around eachother causing tension - sections of chromatid may break off and exchange with sections of another chromatid
46
explain independent segregation of chromosomes and when does it happen
metaphase 1 - pairs of homologous chromosomes at the equator they arrange themselves in random order
47
explain random fertilisation of gametes
during fertilisation, any male gamete can join with any female gamete thousands of new genetic combinations are possible
48
significance of meiosis
sexual reproduction genetic variation
49
difference in mitosis between plant an animal cells
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
difference in meiosis in animal and plant cells
animal- happens in the gametes (sperm and egg) plant- meiosis happens in pollen and the egg
51
difference in cytokinesis in plant and animal cells
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
another difference in cell division between plant and animal cells
plant cells don't have centrioles, still make spindle fibres however animals cells do have them
53
differences between meiosis and mitosis
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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