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Biology Year 12 > 6 - Cell division > Flashcards

6 - Cell division Flashcards

1
Q

what is the cell cycle?

A
  • the process that all body cells in multicellular organisms use to grow and divide.
  • series of stages for a cell to divide into 2 genetically identical daughter cells.
  • starts with one cell already produced by cell division and ends with 2 genetically identical daughter cells being produced.
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2
Q

what are the functions of the cell cycle?

A
  • growth of tissue/organism.
  • replacement of worn out/damaged cells.
  • to repair damaged tissues.
  • asexual reproduction in plants, animals, fungi
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3
Q

end products of cell cycle is?

A

2 genetically identical daughter cells.

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4
Q

stages of cell cycle:

A 
- interphase:
G1 phase
(G1 checkpoint)
S phase
G2 phase
(G2 checkpoint)
- mitotic phase:
mitosis
cytokinesis
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5
Q

G1 phase?

A
  • first growth phase
  • synthesis of proteins
  • organelles replicate
  • cell increases in size
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6
Q

S phase?

A
  • synthesis phase

- each chromosome is replicated in the nucleus

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7
Q

G2 phase?

A
  • second growth phase
  • cell continues to grow in size.
  • energy stores increase
  • duplicated DNA checked for errors
  • proteins needed for cell division are needed.
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8
Q

mitosis?

A

the nucleus divides

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9
Q

cytokinesis?

A

the cytoplasm divides and two cells are produced.

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10
Q

How is the cell regulated?

A
  • by checkpoints.
    they monitor and verify whether the processes at each phase of the cell cycle have been accurately completed before moving onto the next.
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11
Q

G1 checkpoint

A

checks for:

  • cell size
  • nutrients
  • growth factors
  • DNA damage
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12
Q

G2 checkpoint

A

checks for

  • cell size
  • DNA replication
  • DNA damage
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13
Q

spindle assembly checkpoint

A

checks for:

- chromosome attachment to spindle.

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14
Q

G0

A
  • phase when cell leaves the cycle temporarily or permanently
  • differentiation
  • DNA damage
  • as you age, no. of cells that enter G0 increase.
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15
Q

what are the stages of mitosis?

A
  • prophase
  • metaphase
  • anaphase
  • telophase

PMAT

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16
Q

Prophase

A
  • chromosomes condense and thicken (become visible)
  • each chromosome consists of 2 sister chromatids joined at centromere.
  • two centrioles move to opposite poles of cell.
  • spindle fibres attach to specific areas on centromeres and start to move chromosomes to equator of the cell.
  • nuclear envelope disappears.
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17
Q

Metaphase

A
  • individual chromosomes are moved by spindle fibres to align at equator of cell.
  • chromosomes are attached to the spindle fibres by the centromere.
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18
Q

Anaphase

A
  • centromeres holding the pairs of chromatids in each chromosome divide.
  • spindle fibres contract
  • each chromatid is pulled by their centromere to opposite sides of the cell.
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19
Q

Telophase

A
  • chromatids reach opposite sides of the cell
  • chromatids uncoil and become long and thin again.
  • they are now called chromosomes (each chromosome now consists of one chromatid).
  • spindle fibres disappear
  • nuclear envelope reforms and enclose around the chromosomes at each pole.
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20
Q

Cytokinesis

A
  • cytoplasm divides.
  • in animal cells, a cleavage furrow forms to divide the cell surface membrane.
  • forms 2 genetically identical daughter cells.
  • begins in anaphase, ends in telophase.
  • separate process to mitosis.
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21
Q

no of chromatids in the stages of cell division?

A
  • one chromatid per chromosome before replication.
  • two chromatids per chromosome after replication
  • one chromatid per chromosome after mitotic division.
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22
Q

cytokinesis in plant cells?

A
  • cell plate forms, 2 genetically identical daughter cells are formed.
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23
Q

what are homologous chromosomes?

A

homologous pair of chromosomes contain one maternal and one paternal chromatid.

same genes but different alleles.

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24
Q

What is meiosis?

A

the process by which sex cells (gametes) are made in the reproductive organs.

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25
Q

Importance of meiosis?

A
  • gametes are produced
  • promotes genetic variation in offspring.
  • promotes genetic variation and allows for natural selection to take place.
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26
Q

How does genetic variation occur in meiosis?

A
  • crossing over in prophase 1

- independent assortment in metaphase 1

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27
Q

why are gametes haploid?

A
  • they only have one copy of each chromosome
  • 23 chromosomes
  • haploid
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28
Q

why are body cells diploid?

A
  • they have two of each chromosome
  • 46 chromosomes (23 pairs)
  • diploid.
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29
Q

Which cells are diploid and haploid?

A

gametes: haploid

somatic (body) cells: diploid.

30
Q

what are the stages of meiosis?

A
  • interphase
- meiosis 1
prophase 1
metaphase 1
anaphase 1
telophase 1
- meiosis 2
prophase 2
metaphase 2
anaphase 2
telophase 2
31
Q

interphase (meiosis)

A
  • DNA unravels and replicates to produce sister chromatids.
32
Q

prophase 1

A
  • chromosomes condense
  • nuclear envelope dissolves
  • homologous chromosomes form bivalents.
  • centrioles move to opposite poles of cell.
  • crossing over occurs
  • chiasmata form between non-sister chromatids of homologous chromosomes.
  • chromatids have same genes, different combination of alleles.
33
Q

metaphase 1

A
  • spindle fibres from opposing centrioles connect to bivalents (at centromeres) and align along equator of cell.
  • independent assortment occurs
  • orientation of each homologous pair is random and independent to any other homologous pair.
34
Q

anaphase 1

A
  • spindle fibres contract
  • bivalent splits
  • homologous chromosomes move to opposite poles of the cell
35
Q

telophase 1

A
  • chromosomes decondense
  • nuclear envelope may reform
  • cytokinesis occurs to form 2 haploid daughter cells.
36
Q

prophase 2

A
  • chromosomes condense
  • nuclear envelope dissolves
  • centrioles move to opposite poles of cell.
  • spindle fibres reform.
37
Q

metaphase 2

A
  • spindle fibres from opposing centrioles attach to chromosomes at centromere and align them along equator of cell.
38
Q

anaphase 2

A
  • spindle fibres contract
  • sister chromatids separate
  • chromatids (now called chromosomes) move to opposite poles of cell.
39
Q

telophase 2

A
  • chromosomes decondense
  • spindle fibres breaks down
  • nuclear envelope reforms.
  • cell undergoes cytokinesis
  • cytoplasm and cell surface membrane divide, forming ↓
  • 4 independent haploid daughter cells.
40
Q

What is the product of meiosis?

A
  • 4 haploid daughter cells.

- gametes.

41
Q

What are specialised cells?

A
  • cells which are differentiated, meaning that they are specialised to carry out very specific functions.
42
Q

erythrocytes

A
  • transports oxygen around the body.
  • biconcave shape (increases surface area to vol ratio).
  • no nucleus/other organelles. Increases space for available for haemoglobin.
  • flexible: able to squeeze through narrow capillaries.
43
Q

neutrophils

A
  • essential role in immune system.
  • multi-lobed nucleus gives them flexibility
  • granular cytoplasm contains lots of lysosomes that contain hydrolytic enzymes that attack pathogens.
44
Q

squamous cells

A
  • very thin cells

- provides a short diffusion distance for efficient diffusion of gases.

45
Q

ciliated epithelial cells

A
  • cilia

- wafts particles.

46
Q

sperm cells

A
  • function to deliver genetic information to egg cell.
  • flagellum so they can swim to the egg cell.
  • lots of mitochondria to provide energy to swim.
  • acrosome contains digestive enzymes, so they can penetrate the surface of the egg.
47
Q

palisade cells

A
  • present in mesophyll
  • majority of photosynthesis occurs here.
  • Lots of chloroplasts, photosynthesis levels are high here.
  • rectangular shape to form a continuous layer.
  • thin cell walls, increases rate of diffusion of CO2.
  • chloroplasts can move within the cytoplasm to absorb more light.
  • large vacuole maintains turgor pressure.
48
Q

Root hair cells

A
  • absorbs water and mineral ions from soil.
  • large surface area maximises uptake of water and mineral ions.
  • thin cell wall, increases rate of absorption.
  • lots of mitochondria provides energy for active transport.
49
Q

guard cells

A
  • found in pairs with a gap called stoma.
  • when guard cells are turgid, stomata opens.
  • when guard cells are flaccid, stomata closes.
  • thick inner wall, thin outer wall causes them to bend outwards when turgid.
50
Q

What is a tissue?

A

A tissue is a group of differentiated cells that work together to perform a particular function.

51
Q

squamous epithelium

A
  • single layer of flat cells lining a surface.
  • present when rapid diffusion across a surface is essential.
  • found in alveoli in lungs.
  • ## provides a short diffusion distance, allowing a high rate of diffusion of gases in the alveoli.
52
Q

ciliated epithelium

A
  • has hair-like structures called cilia.
  • in trachea, goblet cells are also present which secrete mucus. Cilia waft the mucus away from the lungs to the back of the throat.
  • prevents microorganisms from reaching alveoli in lungs.
53
Q

cartilage

A
  • connective tissue found in joints, outer ear, nose.
  • firm flexible connetive tissue composed of chondrocyte cells in an extracellular matrix.
  • prevents end of bones from rubbing together.
54
Q

Muscle

A
  • tissue that contracts to move bones, which moves different parts of the body.
  • made up of bundles of muscle fibres.
  • muscle fibres separated by connective tissue.
  • smooth
  • cardiac
  • skeletal
55
Q

xylem

A
  • plant tissue
  • transports water and minerals throughout plants.
  • provides structural support
  • travel direction is upwards only.
  • xylem vessel elements which are elongated dead cells.
  • living parenchyma cells.
  • lignin in xylem tissue provides structural support for plants.
56
Q

phloem

A
  • plant tissue
  • transports organic solutes such as sucrose from leaves to rest of plant.
  • travel direction is bidirectional.
  • composed of sieve tube elements, separated by sieve plates (lets phloem content flow through).
57
Q

What is an organ?

A
  • a group of different tissues that work together to perform a specific function.
58
Q

examples of organs?

A
  • lungs
  • contains squamous epithelial tissue, ciliated epithelial tissue.
  • elastic connective tissue and vascular tissue in blood vessels.
  • leaves
  • palisade tissue (photosynthesis)
  • epidermal tissue (prevent water loss)
  • xylem and phloem tissue.
59
Q

What are organ systems?

A

They are systems in which organs work together to perform a specific function.

60
Q

examples of organ systems?

A
  • digestive system
  • cardiovascular system
  • gaseous exchange system.
61
Q

What is a stem cell?

A

a renewing source of undifferentiated cells. They have a potential to become specialised.

62
Q

Where are embryonic stem cells found?

A

blastocyst

63
Q

order of potency of stem cells? from least potent?

A
  • unipotent
  • multipotent
  • pluripotent
  • totipotent
64
Q

potency of embryonic stem cells?

A

totipotent for 7 days after start of embryo development and pluripotent after the blastocyst forms.

  • they can differentiate into almost every cell type under the correct lab conditions.
65
Q

Replacement of red and white blood cells using stem cells?

A
  • adult stem cells in the bone marrow.

- they differentiate to replace worn out erythrocytes and neutrophils.

66
Q

Where are stem cells present in plants?

A

meristems

67
Q

What do stem cells in plants differentiate into?

A

stem cells in the meristems in the vascular cambium of plants differentiate into xylem vessels and phloem sieve tubes.

68
Q

stem cells for treating burns?

A
  • stem cells can be used to create skin grafts to treat burns.
69
Q

stem cells for treating Alzheimer’s?

A
  • nerve cells die in increasing numbers.

- hope to use stem cells to regrow healthy nerve cells

70
Q

stem cells for treating Parkinson’s’?

A
  • caused by death of dopamine-producing cells in the brain.

- stem cells may help to regenerate the dopamine-producing cells.

71
Q

research into developmental biology?

A
  • stem cells can be used to research about how organisms grow and develop.
  • can help us to understand more about developmental disorders and cancer.

Biology Year 12 (11 decks)

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