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A-level biology > 2.1.6 - cell division, cell and organisation > Flashcards

2.1.6 - cell division, cell and organisation Flashcards

(63 cards)

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1
Q

what are the 4 stages of the cell cycle

A

G1, S, G2 and M (mitosis)

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2
Q

what happens in G1

A

the cell grows and inc size
transcription of DNA to mRNA
organelles duplicate
biosynthesis happens

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3
Q

what is biosynthesis

A

where the enzymes needed for the other stages are made

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4
Q

what gene controls G1

A

p53 (tumour suppressor gene) controls this phase and stops excess growth

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5
Q

what can happen if the p53 gene doesn’t control the cell growth

A

cell may grow too much and develop into a tumour which could be cancerous

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6
Q

what happens at the early G1 checkpoint

A

if the cell isn’t progressing properly, it enters G0

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7
Q

what happens at G0

A

the cell enters to be repaired or sometimes it may have to stay there permanently

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8
Q

what are the reasons that a cell may enter G0 permanently

A

if it has differentiated into a cell that doesn’t go through mitosis
if the DNA is beyond repair

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9
Q

what happens to a cell in G0 if it is beyond repair

A

apoptosis (controlled cell death)
senescence (cell ages until death)

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10
Q

what happens at the G1/S checkpoint

A

if the cell is damaged, it won’t enter the S phase

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11
Q

what happens in the S phase (replication phase)

A

the DNA duplicates

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12
Q

why is the S phase rapid

A

to reduce the chance of mutations

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13
Q

what is the order of the genes that are duplicated in the S phase

A
  1. housekeeping genes (genes switched on in all cell types)
  2. genes active in that cell type
  3. genes normally switched off in that cell type
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14
Q

what happens at the DNA synthesis checkpoint

A

checks that DNA is replicated properly before entering G2

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15
Q

what happens in G2

A

additional growth
energy stores replenished
cytoskeleton dismantled
organelles arranged in the cytoplasm

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16
Q

what happens at the G2/M checkpoint

A

final check before mitosis and special chemicals are produced to help from spindle fibres

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17
Q

what is the M phase

A

where mitosis happens

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18
Q

what happens at the M checkpoint

A

happens 1/2 way through mitosis
the cell won’t enter anaphase if chromosomes aren’t attracted to spindle fibres

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19
Q

what happens during cytokinesis

A

cell membranes and cytoplasm divide to produce 2 genetically identical daughter cells

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20
Q

what happens during prophase in mitosis

A
  • chromosomes condense
  • the nuclear envelope breaks down into vesicles
  • the spindle fibres are formed
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21
Q

what is each chromosome in prophase made of and how is it held together

A

each chromosomes is made of 2 sister chromatids which are held by a centromere

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22
Q

what makes spindle fibres

A

the centrioles make tubulin which makes up the spindle fibres

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23
Q

what happens during mitosis metaphase

A
  • chromosomes align along the equator (metaphase plate)
  • spindle fibres attach to centromeres
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24
Q

what happens in mitosis anaphase

A
  • sister chromatids pulled apart to opposite poles of the cell
  • centromere divides
  • chromatids are called chromosomes again
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25
how are the sister chromatids pulled apart
by the motor proteins 'walking' along the spindle fibres
26
what happens during mitosis telophase
nuclear membrane reforms from vesicles spindle fibres disappear and chromosomes uncoil
27
why is the nuclear membrane kept in vesicles
because it saves energy rather than rebuilding from scratch
28
what are the mitosis daughter cells identical to
the parent cell and eachother
29
the parent ell of meiosis is diploid. What does that mean
there are 2 copies of each chromosome one each from the mother and father
30
what happens in meiosis prophase 1
chromosomes condense nuclear membrane breaks down into vesicles centrioles make spindle fibres the chromosomes are made of sister chromatids held by a centromere recombination occurs
31
what is recombination
non sister chromatids wrap around each other and exchange sections of DNA
32
what is the bivalent
the 2 non sister chromatids crossing over
33
what is the chiasma
the specific part where the 2 non sister chromatids cross over during recombination
34
what happens in meiosis metaphase 1
homologous pairs (still crossed over) line up at the equator spindle fibres attach to centromere independent assortment of chromosomes and independent segregation of chromosomes
35
what is independent assortment of chromosomes
homologous pairs align randomly at the equator and could be on either side
36
what is independent segregation of chromosomes
how they line up on the equator which determines how they are pulled apart during anaphase
37
what happens during meiosis anaphase 1
homologous chromosome pairs pulled to opposite poles by motor proteins each chromosome made of 2 non sister chromatids centromeres still holding chromatids together crossed over section pulled apart
38
what happens during meiosis telophase 1
2 new nuclei form from the vesicles spindle fibres disappear chromosomes uncoil
39
what is the purpose of meiosis 1
halves the chromosome number
40
what happens in meiosis prophase 2
nuclear membrane breaks down into vesicles chromosomes condense centrioles make spindle fibres chromosomes still made of 2 chromatids
41
are the chromatids in the chromsomes during prophase 2 sister or non sister
non sister due to the crossing over in prophase 1
42
what happens in meiosis metaphase 2
chromosomes line up at the equator spindle fibres attach to centromere random assortment and random segregation occur
43
what is random assortment of chromatids
chromatids are arranged randomly and either side can be facing either pole
44
what is random segregation of chromatids
how they arrange themselves along the equator determines how they are pulled apart in anaphase 2
45
what happens in anaphase 2
chromatids pulled to opposite poles by motor proteins walking along spindle fibres centromere divides
46
what happens during telophase 2
spindle fibres disappear and nuclear membrane reforms
47
what is the end product of meiosis
4 genetically non identical daughter cells that are different to the parent and each other
48
what is the purpose of meiosis 2
separates chromatids and each nucleus has the correct number of chromosomes and genetic material
49
what is variation caused by
independent assortment and segregation, random assortment and segregation, random fertilisation
50
where do embryonic stem cells come from
2-5 day old embryos
51
what can embryonic stem cells differentiate into
any cell in the body
52
where are adult stem cells from
from certain locations in the body - eg bone marrow
53
pros of embryonic stem cells
can differentiate into any cell uses 'wasted' embryos from IVF
54
cons of embryonic stem cells
ethical issues destroying embryo expensive immunosuppressants needed
55
pros of adult stem cells
no rejection as own cells used no immunosuppressants needed no embryos involved
56
cons of adult stem cells
only found in certain locations can only differentiate into the type of cell where it is found can be painful to extract
57
what are stem cells
undifferentiated cells that can express all genes and can self renew
58
what is totipotent
can differentiate into any cell in the body and placental cells
59
what is pluripotent (embryonic)
any cell in the body but not placental
60
what is multipotent (adult)
can only be limited cell types
61
multipotent animal stem cell example
bone marrow - can only become blood cells and genes switch on/off to determine type of blood cell
62
multipotent plant example
meristem - inner meristem is xylem and outer meristem is phloem. the level of hormones determine if it is xylem or phloem
63
what are induced pluripotent stem cells
created by programming differentiated cells to switch on/off key genes which enables them to become undifferentiated made from the patients own cells so no rejections so no immunosuppressants needed

A-level biology (25 decks)

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