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biology module 2 > cell division and stem cells > Flashcards

cell division and stem cells Flashcards

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1
Q

what is the difference between mitosis and meiosis

A

mitosis only involves 1 division and produces 2 genetically identical diploid daughter cells

meiosis involves 2 divisions and produces 4 genetically different haploid daughter cells

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2
Q

what are 3 functions of mitosis

A
  • growth + repair + replacement of tissues in multicellular organisms
  • asexual reproduction in plants or unicellular organisms
  • development of embryos
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3
Q

what are the 2 main phases in the cell cycle

A

interphase and mitotic phase

cell spends most of the time in interphase

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4
Q

what is interphase

A

the long periods of growth and normal functioning that takes place between divisions

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5
Q

what are the 3 stages within interphase

A

G1 S G2

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6
Q

what occurs during G1

A

first growth phase
- protein production
- organelle replication
- cell grows in size

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7
Q

what occurs during S phase

A

synthesis phase
- DNA replication occurs
DNA is unravelled and replicated with high priority sequences going first

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8
Q

what occurs during G2

A

second growth phase
- energy stores increase
- duplicated DNA is checked
- cell grows in size

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9
Q

what are the 4/5 stages in mitotic phase

A

prophase
metaphase
anaphase
telophase
(cytokinesis)

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10
Q

what occurs during prophase of mitosis

A
  • chromatin fibres coil and condense to form chromosomes
  • cell poles are linked by spindle fibres made of microtubules, which move chromosomes into the centre
  • nucleolus + nuclear envelope break down
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11
Q

what occurs during metaphase of mitosis

A
  • chromosomes move to metaphase plate in the centre of the cell, where they are held in place by spindle fibres
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12
Q

what occurs during anaphase of mitosis

A
  • centromeres holding together chromatid pairs divide as cohesion proteins are cleaved
  • spindle fibres shorted and pull pairs apart to opposite poles
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13
Q

what occurs during telophase of mitosis

A
  • chromatids reach poles and are now called chromosomes
  • chromosomes assemble at each pole and uncoil
  • nucleolus + nuclear envelope reform
  • remaining spindle fibres are broken down
  • 2 daughter nuclei have been formed
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14
Q

what occurs during cytokinesis

A

this is the actual cell division - forms 2 daughter cells
- microfilaments form a ring around the edge of cell surface membrane
- this pulls membrane inwards, pinching the cell in two
- membrane fuses in the middle therefore 2 separate cells made

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15
Q

what is G0 of the cell cycle

A

this is when cells leave the cell cycle, either temporarily or permanently - checkpoints

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16
Q

chromatid definition

A

each of the 2 strands a chromosome divides into

2 chromatids are held together at a centromere

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17
Q

chromatin definition

A

uncondensed DNA which is in complex histone proteins, that forms chromosomes

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18
Q

chromosomes definition

A

a form of condensed and coiled DNA molecules made up of chromatin associated with histones

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19
Q

centromere definition

A

the region at which 2 identical sister chromatids are held together

this is also where the spindle fibres attach to pull sister chromatids apart during cell division

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20
Q

spindle fibres definition

A

a structure made of microtubules and associated proteins that assemble from the centrosome to move chromosomes around

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21
Q

homologous pairs definition

A

a pair of chromosomes - 1 maternal and 1 paternal - that contain the same genes on the same loci, but do not necessarily have the same alleles

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22
Q

why does DNA form chromosomes during cell division

A

this structure helps to protect DNA from damage when it is being moved and relicated

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23
Q

why does DNA wrap around histones

A

it makes the DNA more compact

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24
Q

what is mitosis in bacteria called

A

binary fission

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25
Q

diploid definition

A

cells with a full set of chromosomes, 2 of each type, each inherited by 1 parent

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26
Q

haploid definition

A

a cell with only half the normal number of chromosomes, just one of each type

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27
Q

gametes definition

A

haploid sex cells made by meiosis in organisms that reproduce sexually

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28
Q

zygote definition

A

the initial diploid cell formed when nuclei of 2 gametes fuse during fertilisation

29
Q

what are the 4 ways meiosis allows for variation to occur

A
  • crossing over to form recombinant chromatids
  • random assortment
  • mutations
  • random fertilisation of 2 gametes
30
Q

what is crossing over

A

when sections of DNA become entangled, causing them to break and rejoin, causing DNA exchange, forming recombinant chromatids

31
Q

chiasmata definition

A

the point at which crossing over occurs

32
Q

what is random assortment

A

in metaphase, the orientation of each pair as it lines up is random so many combinations are possible

33
Q

mutation definition

A

random changes in DNA that create different alleles

34
Q

what is fertilisation

A

when 2 gamtes fuse together to form a diploid cell called a zygote, with a new unique combination of DNA

35
Q

recombinant chromatids definiton

A

chromatids with a combination of DNA from both homologus chromosomes formed by crossing over chiasmata

36
Q

where can crossing over occur in meiosis

A

prophase 1

37
Q

where does independent assortment occur in meiosis

A

metaphase 1 + 2

38
Q

why might cells enter G0

A
  • differentiation - specialised cells cannot divide, except for lymphocytes
  • damage to cell DNA makes cells unviable for cell division, therefore enters permanent cell arrest
39
Q

senescent definition

A

aged cells that must stop dividing

40
Q

why are senescent cells harmful

A

senescent cells tend to build up with age, this has been linked to a number of age related diseases e.g. cancer and arthrits

41
Q

cancer definition

A

a group of diseases caused by the uncontrolled division of cells that form abnormal cell masses called tumours

42
Q

benign vs malignant

A

benign = no growth, don’t travel
malignant travels constantly and constantly grows

43
Q

what could cause tumours to build up?

A

tumours can be caused by the damage or mutation of genes that encode for cell-cycle regulation proteins

overexpression of this mutated gene will disrupt cell cycle regulation, and can potentially result in the formation of tumours

44
Q

stem cells definition

A

undifferentiated cells with the potential to differentiate into a variety of specialised cell types in an organism

45
Q

what is 1 important characteristics of stem cells

A
  • can repeatedly undergo cell division
46
Q

what are 3 functions of stem cells used for in the body

A
  • growth
  • embryo development
  • tissue repair
47
Q

totipotent definition

A

stem cells with full potential to differentiate into any type of cell

  • found in embryos (zygotes) and meristems
  • enough to form a whole new organism
48
Q

pluripotent definition

A

potential to differentiate into any type of cell
- collected from early stages of an embryo (blastocyst) or cambium tissue in plants
- unable to form a whole new organism

49
Q

multipotent

A

stems cells with the potential to differentiate into only a certain number of cells

e.g. haematopoietic cells and blood cells on bone marrow

50
Q

objections to stem cell research

A
  • cell division is uncontrollable which can lead to cancers
  • ethical issues with takin embryonic stem cells of foetal stem cells
51
Q

examples of a specialised cell - erythrocytes

  • what is it
  • where are they made and found
  • function
  • adaptations
A

red blood cell

made in bone marrow and found in blood, carried around by blood plasma

carries O2 around body and takes CO2 to lungs for exhalation

adaptations:
- small and flexible to fit in capillaries
- biconcave shape for high SA:V
- thin membrane for more efficient diffusion
- haemoglobin which reversibly binds to O2
- no nucleus so more space in cell

52
Q

examples of a specialised cell - neutrophils

  • what is it
  • where are they made and found
  • function
    adaptations
A

a type of white blood cell that destroys pathogens via phagocytosis

produced in bone marrow and found in blood plasma

primary response to invasion of pathogens

adaptations:
- flexible so fits through capillaries
- lots of lysosomes to help digest pathogens
- lobed nucleus increases cell flexibility

53
Q

examples of a specialised cell - sperm cells

  • what is it
  • where are they made and found
  • function
  • adaptations
A

a gamete produced by males

found and made in testes of males who have reached sexual maturity

fuses with egg cells in reproduction to pass on fathers genes to offspring

adaptations:
- haploid nucleus so can fuse with egg cell to make a diploid cell and increases variation
- digestive enzymes helps it to break down outer layer of egg
- lots of mitochondria allows for tail movement
- rotating tail increases motility

54
Q

examples of a specialised cell - root hair cell

  • what is it
  • where are they made and found
  • function
  • adaptations
A

single celled extensions on plant roots that absorb water + minerals from soil

found on epidermal cells on roots

absorbs mineral ions and water from soil

adaptations:
- root hair increases SA:V
- thin walls for more efficient diffusion
- vacuole maintains water potential gradient
- lots of mitochondria allows for active transport of mineral ions
- no chloroplasts as no light underground

55
Q

examples of a specialised cell - ciliated epithelial cells

  • what is it
  • where are they made and found
  • function
  • adaptations
A

a type of cell covered in hair like projections called cilia

found lining respiratory tract and fallopian tubes

moves substances e.g. mucus across surface of a tissue

adaptations:
- cilia beat to shift material along surface of tissue
- goblet cells secrete mucus

56
Q

examples of a specialised cell - squamous epithelial cells

  • what is it
  • where are they made and found
  • function
  • adaptations
A

large polygonal cells with small round nucleus

found in epidermis of skin and lining lungs, mouth and cervix

provides an outer layer/surface

adaptations:
- single layer of cells for more efficient diffusion
- permeable for easy diffusion

57
Q

examples of a specialised cell - palisade cells

  • what is it
  • where are they made and found
  • function
    adaptations
A

plant leaf cells containing chlorophyll

located on upper side of leaf, below epidermis and waxy cuticle

carries out photosynthesis

adaptations:
- lots of chloroplasts to maximise light absorption
- tall and thin shape allows deeper penetration of light

58
Q

examples of a specialised cell - guard cells

  • what is it
  • where are they made and found
  • function
    adaptations
A

pairs of curved cells surrounding stomata that can become larger or smaller depending on pressure

located in epidermis of leaf, surrounding stomatal pores

controls opening of stomata through turgor pressure to regulate water loss

adaptations:
- thick inner cell wall than outer cell wall allows cell to bend when turgid to open stomata
- lots of chloroplasts and mitochondria as likely play a role in stomatal opening

59
Q

tissue definition

A

a collection of differentiated cells with a common function

60
Q

organ definition

A

a group of tissues working together to carry out a common function

61
Q

organ system definition

A

a group of organs that carry out a common fucntion

62
Q

specialised definition

A

having a particularly adapted structure to serve a particular function

63
Q

differentiation definition

A

the process by which less specialised cells develop distinct forms and function to become specialised

64
Q

what are 2 reasons that multicellular organisms need specialised cells

A
  • complex communication in multicellular organisms
  • specialised functions need specialised cells to maximise efficiency of processes e.g. nutrient absorption
65
Q

potency definition

A

the ability of a stem cell to differentiate into different cell types

66
Q

how do cells become specialised

A
  • all cells have the same DNA
  • genes are switched on and off by epigenetics
  • this controls what proteins are produced in the cell
  • therefore the cell can undergo a specialised function
67
Q

mitotic index definition

A

the proportion of cells in a specific stage of mitosis

68
Q

where are the checkpoints

A
  • G1 - chromosomes are checked for damage, if this is detected the cell doesn’t advance unto S phase
  • S - chromosomes are checked to ensure replication have occurred successfully, if not cell doesn’t continue in cycle
  • G2 - an additional check for DNA damage occurs after DNA has been replicated, cell cycle will be delayed until any necessary repairs are made
  • metaphase - final check determines whether chromosomes are correctly attached to spindle fibres

biology module 2 (10 decks)

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