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Biology > 12.6 Cell Cycle & Cell Division > Flashcards

12.6 Cell Cycle & Cell Division Flashcards

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1
Q

what is the first stage of the cell cycle called

A

interphase

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2
Q

what 3 stages is interphase divided into

A

G1 phase (gap 1)
S phase (synthesis)
G2 phase (gap 2)

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3
Q

what happens in G1 phase

A

cell increases in size / volume and new biomass is made (proteins)

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4
Q

what happens in S phase

A

DNA replicates by semi-conservative DNA replication

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5
Q

what happens in G2 phase

A

cell prepares for division, synthesis and stores of ATP and new organelles synthesised

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6
Q

nuclear division (mitosis or meiosis) definition

A

period when the nucleus divides into 2 (mitosis) or 4 (meiosis)

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7
Q

cell division (cytokinesis) definition

A

division of the cytoplasm which follows nuclear division and is the process by which the cytoplasm divides to produce 2 new cells (mitosis) and 4 new cells (meiosis)

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8
Q

why does the mass of a cell in the cell cycle overall increase

A
  • G1 -> cell gets bigger -> more mass
  • S -> DNA replication
  • Mitosis -> organelle replicate
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9
Q

why does the mass of DNA in the cell cycle increase and then decrease

A

increases in S phase -> DNA replication
decreases in mitosis -> DNA contents halves as cell divides into 2 during cytokinesis

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10
Q

gene definition

A

a section of DNA that codes for 1 specific polypeptide (protein)

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11
Q

the base sequence of DNA on the DNA codes for…

A

the sequence of amino acids in a protein

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12
Q

chromosome definition

A

an independent DNA molecule which has been supercoiled into a condensed form

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13
Q

unduplicated chromosome is called

A

chromatid

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14
Q

duplicated chromosome is called

A

identical sister chromatids

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15
Q

central point in chromosome is called

A

centromere

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16
Q

how is identical sister chromatids formed

A

DNA starts to coil around histones
DNA supercoils and condenses
Forms identical sister chromatids

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17
Q

why do complex organisms have a number of chromosomes

A

they have a large number / many different genes

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18
Q

what is a chromosome number

A

the number of different chromosomes possessed by an organism

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19
Q

the chromosome number is represented by the letter…

A

n

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20
Q

diploid (chromosome number)

A

2n

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21
Q

haploid (chromosome number)

A

n

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22
Q

draw a single unduplicated chromosome

A
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23
Q

draw a single duplicated chromosome

A
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24
Q

a single unduplicated chromosome. before or after S phase

A

before S phase

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25
Q

a single duplicated chromosome. before or after S phase

A

after S phase

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26
Q

(3 things) mitosis is used for…

A
  • increasing cell numbers and growth of an organism
  • repair of damaged tissues (not cells)
  • replacement of worn out / dead cells
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27
Q

what happens before mitosis

A

semi conservative replication of DNA

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28
Q

does variation occur in mitosis

A

no

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29
Q

what can the 2 daughter cells be called in relation to their parent cell

A

genetically identical clones (same alleles of same genes in the same gene loci)

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30
Q

can mitosis be used for asexual reproduction

A

yes

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31
Q

when will mitosis occur in some organisms for asexual reproduction (what environment)

A

tends to occur in favourable, stable environments (no environmental change)

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32
Q

order of stages in mitosis

A
  • prophase
  • metaphase
  • anaphase
  • telophase
  • cytokinesis
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33
Q

key points of prophase

A
  • the nuclear membrane starts to break down
  • the centrioles start to move to the poles of the cell and make spindle fibres
  • the chromosomes supercoil and condense / shorten / thicken and become visible
  • each chromosome appears as 2 identical sister chromatids joined at the centromere
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34
Q

prophase microscope hint

A

you first see the chromosomes properly / visible

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35
Q

key points of metaphase

A
  • the centrioles complete the production of spindle fibres (contractile protein fibres)
  • the chromosomes are attached to the spindle fibres by their centromere
  • the chromosomes align down the equator of the cell
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36
Q

metaphase microscope hint

A

the chromosomes look like they line up in the middle / equator

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37
Q

key points of anaphase

A
  • the spindle fibres contract / shorten
  • the centromere splits
  • the identical sister chromatids are pulled to opposite poles
  • making a ‘V’ shape
38
Q

anaphase microscope hint

A

chromosomes are pulled apart, they look v shaped

39
Q

key points of telophase

A
  • a nuclear membrane starts to reform around each set of chromosomes
  • the chromatids / chromosomes unwind / uncoil / become longer / thinner and become invisible
40
Q

telophase microscope hint

A

the chromosomes have split and clustered into 2 nuclei

41
Q

what happens in cytokinesis

A

separation of the cytoplasm

42
Q

allele definition

A

different version of the same gene

43
Q

gene definition

A

section of DNA on a chromosome coding for 1 or more polypeptide

44
Q

chromosome definition

A

independent DNA molecule in a condensed form which contains many genes (using histones)

45
Q

sister chromatid definition

A

1 of the 2 strands of a replicated chromosome that are joined together by a single centromere prior to cell division

46
Q

haploid definition

A

cell that contain only a single copy of each chromosome

47
Q

diploid definition

A

cell in which the nucleus contains 2 sets of homologous chromosomes

48
Q

somatic cell definition

A

a normal body cell

49
Q

homologous chromosomes definition

A

same genes are in the same location

50
Q

cancer definition

A

cells that undergo rapid uncontrolled mitosis

51
Q

which control genes are used to switch cell division on and off

A
  • tumour suppressor genes
  • proto-onco genes
52
Q

what do tumour suppressor genes code for

A

code for proteins that slow down the cell cycle

53
Q

what do proto-onco genes do

A

code for proteins that speed up the cell cycle

54
Q

formation of cancer

A
  • if a mutation occurs in 1 if these control genes, then cell division continues, uncontrolled
  • it’s often rapid and the cells produced are abnormal
  • a tumour develops
  • if these cells start to spread into the surrounding tissues / body, the tumour is regarded as a cancer
55
Q

what is a tumour

A

a mass of abnormal cells

56
Q

1 method used to treat cancer

A

give drugs that inhibit cell division (mitosis)

57
Q

what do these drugs stop

A

DNA replication, spindle formation, cytokinesis

58
Q

where does binary fission occur

A

in prokaryotic cells

59
Q

what type of reproduction is binary fission

A

asexual reproduction

60
Q

process of binary fission

A
  • replication of the circular DNA (not associated with histones) and of plasmids
  • cell elongates from the middle separating the 2 DNA molecules attached to different parts of the cell membrane
  • a new murein cell wall is formed down the middle of the elongated cell which eventually meets, dividing the cell in 2
  • division of the cytoplasm to produce 2 daughter cells, each with a single copy of the circular DNA and a variable number of copies of plasmids
61
Q

which organelles are NOT used in binary fission

A

no nucleus, no chromatids, no centrioles, no spindle fibres

62
Q

how long does the process of binary fission take

A
  • its very fast
  • bacteria doubles every 20 mins
63
Q

what is the endosymbiont theory

A
  • mitochondria and chloroplasts can also replicate by binary fission
  • gives evidence that these organelles perhaps were once prokaryotes
64
Q

are viruses cellular (living) or acellular (non-living)

A

acellular (non-living)

65
Q

how do viruses replicate

A

can only replicate inside host cells

66
Q

process of viral replication

A
  • attachment proteins on the virus attach to the receptors on the cell
  • the virus nucleic acid enters the cells cytoplasm
  • reverse transcriptase makes DNA from viral RNA
  • the viruses DNA is inserted into the host cells own nuclear DNA / genome
  • the viral DNA is transcribed (viral mRNA) and translated into viral proteins (capsids / enzymes / attachment proteins)
  • the cell replicates the viral DNA
  • the genetic material and proteins coats are assembled into virions
  • eventually these virions burst out of the cell, often destroying the host cell
67
Q

summary of virus replication

A

use the host cell enzymes to replicate and transcribe viral DNA into viral mRNA and translate viral proteins, making more virus particles which then burst out of the cell

68
Q

why is the plant sample soaked in 50C HCl (mitosis -> practical skills)

A

to break down the cellulose cell walls (breaks H bonds that hold microfibrils together), ensuring the stain can enter and the tissue and the root tissue can be squashed into a single layer, 1 cell thick, so that light passes through the thin sample of tissues / cells

69
Q

why is the plant sample soaked in ethano-orcein stain / potassium iodide (mitosis -> practical skills)

A

to stain the chromosomes (adds contrast) so they can be viewed under the microscope

70
Q

equation of mitotic index =

A

(number of cells in PMAT) / (total number of visible cells)

71
Q

the greater the MI value =

A

faster rate of cell division

72
Q

dilution series equation

A

M1 x V1 = M2 x V2

72
Q

equation for the length of time each stage of mitosis takes by using a variation of mitotic index

A

(total number of cells in mitosis - visible chromosomes) / (total number of visible cells) x time of 1 cell cycle (minutes)

72
Q

(dilution series equation) where V1 equals…

A

desired volume (cm3)

73
Q

(dilution series equation) where M1 equals…

A

desired diluted concentration (mol dm-3)

74
Q

(dilution series equation) where M2 equals…

A

original concentration (mol dm-3)

75
Q

(dilution series equation) where V2 equals…

A

unknown volume of stock solution (cm3)

76
Q

draw and label the stages of meiosis with 2 homologous pairs of chromosomes

A
77
Q

draw and label the stages of meiosis with 3 homologous pairs of chromosomes

A
78
Q

stages of meiosis (P1 & M1 -> meiosis 1 -> nuclear division 1)

A
  • chromosomes supercoil, condense (around histones) and become visible
  • homologous pairs of chromosomes pair up (form a bivalent) and align along the equator
  • spindle fibres attach to the centromere
  • crossing over and independent segregation occurs here
79
Q

stages of meiosis (A1 -> meiosis 1 -> nuclear division 1)

A

spindle fibres contract and separate homologous chromosome pairs, pulling 1 of each pair to opposite poles of the cell

80
Q

stages of meiosis (T1 -> meiosis 1 -> nuclear division 1)

A

nuclear membrane reforms around the separated homologous chromosomes

81
Q

stages of meiosis (conclusion -> meiosis 1 -> nuclear division 1)

A

each daughter cell is now HAPLOID (n)

82
Q

stages of meiosis (P2 -> meiosis 2 -> nuclear division 2)

A

each daughter cell only contains 1 chromosome from each homologous pair (haploid)

83
Q

stages of meiosis (M2 -> meiosis 2 -> nuclear division 2)

A

each chromosome aligns along the equator

84
Q

stages of meiosis (A2 -> meiosis 2 -> nuclear division 2)

A

non-sister chromatids are split by their centromere and pulled to opposite polls of the cell

85
Q

stages of meiosis (T2 -> meiosis 2 -> nuclear division 2)

A

nuclear membrane reforms

86
Q

stages of meiosis (conclusion -> meiosis 2 -> nuclear division 2)

A

4 genetically different haploid daughter cells are produced

87
Q

key points of crossing over

A
  • chromosomes being moved during P1 and M1 of meiosis 1
  • the homologous chromosomes associate / bivalent is formed
  • chiasmata form (chromosomes entangle / twist)
  • equal lengths of non-sister chromatids / alleles are exchanged
  • producing new combinations of alleles
88
Q

key points of independent segregation

A
  • during M1 of meiosis 1
  • homologous chromosomes attach to the spindle fibres
  • they pair up side by side
  • can be reshuffled in any combination
  • on equator of the cell
88
Q

equation for calculating the possible number of different combinations of chromosomes following meiosis, without crossing over

A

2^n where n = the number of different pairs of homologous chromosomes

88
Q

5 differences between meiosis and mitosis

A

MEI -> genetically different (daughter cells)
MIT -> genetically identical (daughter cells)

MEI -> homologous chromosomes associate in pairs
MIT -> chromosomes do not pair

MEI -> reduced the chromosome number
MIT -> maintains the chromosome number as in the parent nucleus

MEI -> crossing-over / chiasmata formation
MIT -> no crossing-over

MEI -> 2 divisions OR -> 4 offspring (daughter) cells
MIT -> 1 division OR -> 2 offspring (daughter) cells

Biology (10 decks)

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