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BIO230 Final > Week 9 > Flashcards

Week 9 Flashcards

1
Q

What does multicellular development require?

A
  • different fates
  • cell proliferation
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2
Q

What is cellular differentiation?

A

the acquisition of specialized cell functions (cell fates) via differential genome expression

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3
Q

What do different cell fates require?

A

differential genome expression

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4
Q

How can cell fate be acquired?

A

two ways:
- asymmetric division: child cells are born with different fates
- symmetric division, then perception of a signal: child cells are born the same, but acquire different fates

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5
Q

How does asymmetric division contribute to cell differentiation?

A

specific proteins or cell fate markers are unevenly distributed before division, leading one daughter cell to inherit more of these determinants, thus acquiring a different fate

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6
Q

What are the requirements for successful asymmetric division?

A

requires correct spindle alignment during mitosis and proper cytokinesis to ensure that cell fate markers are unevenly placed between the daughter cells

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7
Q

What are the primary mechanisms by which cell fate can be acquired after symmetric division?

A
  1. Lateral inhibition
  2. Induction by diffusible signals
  3. other mechanisms (not in this course)
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8
Q

What is lateral inhibition in the context of cell fate determination?

A

cells that start off the same can develop different fates due to small initial differences that are amplified by molecular mechanisms

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9
Q

How does lateral inhibition create a pattern of differentiated cells?

A

creates a pattern of isolated differentiated cells in a field of relatively undifferentiated cells by having one cell “win” the inhibition competition

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10
Q

What role does Notch signaling play in lateral inhibition?

A

a key example of lateral inhibition, where the activation of Notch in one cell inhibits the expression of Delta in neighboring cells

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11
Q

What is the significance of Delta in Notch signaling?

A
  • a ligand that activates Notch signaling in adjacent cells
  • when one cell expresses Delta and activates Notch in its neighbors, it inhibits their differentiation
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12
Q

How does the interaction between Delta and Notch affect cell differentiation?

A

creates a feedback loop where Delta activates Notch, which in turn inhibits further Delta expression in neighboring cells

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13
Q

What are diffusible signals in the context of cell differentiation?

A

morphogens
- signaling molecules that can affect cell differentiation by diffusing through tissues and acting on nearby cells

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14
Q

How do morphogens influence cell fate?

A
  • by creating concentration gradients
  • cells respond to varying concentrations of morphogens, leading to different cell fates based on the level of exposure
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15
Q

What is the typical outcome of morphogen signaling in a developing tissue?

A

creates a pattern of bands or rings of differentiated cells

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16
Q

What factors influence the diffusion range of a morphogen?

A
  • the amount produced
  • the duration of production
  • the diffusion rate of the signal
  • the stability of the morphogen
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17
Q

Can cells respond differently to the same morphogen?

A

Yes, based on the concentration they receive

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18
Q

What experimental evidence supports the role of morphogens in tissue patterning?

A
  • Transplant experiments, they can induce structures that the host would not normally produce.
  • If they weren’t organizer tissues nothing would’ve happened (morphogens are secreted to create the structure)
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19
Q

What is the role of organizer tissues in the context of morphogen signaling?

A

secrete morphogens

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20
Q

What happens when two copies of organizer tissue were transplanted on the embryo?

A

Two dorsal sides are created along with a shared ventral side

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21
Q

What happens when a cell recieves more signals?

A

it becomes increasingly differentiated

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22
Q

What are totipotent cells?

A

can become any cell type (usually only cells very early after fertilization)
ex: fertilized egg

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23
Q

What are pluripotent cells?

A

can become any adult cell
ex: blastomeres

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24
Q

What are multipotent cells?

A

can become multiple cell types
ex: all gasturlation cells

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25
Q

How can multiple signals overlap during cell fate determination?

A

to create complex patterns of differentiation

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26
Q

What is the concept of combinatorial signaling?

A

the idea that cells exposed to different combinations of signals can adopt distinct fates

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27
Q

What is sequential induction in the context of developmental biology?

A

cells are exposed to different signals over time, leading to a series of decisions that determine their fate

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28
Q

How does sequential induction contribute to the generation of regulatory hierarchies?

A

allows for the establishment of a hierarchy where earlier signals can influence the response to later signals

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29
Q

Decribe a sequential induction example.

A
  • cell type A and B side by side
  • cell type B secrets a morphogen to create cell type C between A and B (ACB)
  • Cell type B and C secret morphogens to create D between A and C and E between C and B
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30
Q

What is the relationship between transcription factors and sequential induction?

A

play a crucial role in sequential induction by determining how cells respond to signals over time

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31
Q

Why is the timing of signals important in sequential induction?

A

it influences the order in which genes are activated or repressed

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32
Q

What is segmentation in the context of animal development?

A

the body of an animal is divided into repeated units or segments

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33
Q

What is the regulatory hierarchy of segmentation in animal bodies?

A
  1. anterior-posterior
  2. Define head, thorax, and abdomen
  3. segments within head, thorax, and abdomen
  4. polarity within each segment
  5. body parts develop from segments
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34
Q

What are Hox genes?

A
  • a group of related genes that determine which body parts will develop from a segment
  • They encode transcription factors that regulate the expression of other genes involved in development
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35
Q

How are Hox genes organized on chromosomes?

A
  • organized into a Hox complex on chromosomes
  • their order corresponds to the order of expression along the anterior-posterior axis of the organism
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36
Q

How many copies of the Hox gene do humans have?

A

4

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37
Q

What is the consequence of Hox gene mutations?

A

Loss or gain of function Hox gene mutants cause body parts to develop in a segment where they shouldn’t normall be

38
Q

What is the primary function of healthy tissues?

A

require maintenance, which includes molecular turnover and cellular turnover

39
Q

What are the two types of cellular turnover?

A
  1. Molecular turnover: Involves the replacement of old molecules with new ones (e.g., proteins, lipids).
  2. Cellular turnover: Involves cell division and cell death
40
Q

How do new cells arise?

A
  • stem cell divison (often)
  • differentiated cell division (sometimes)
41
Q

What are some examples of differentiated cell division?

A
  • liver hepatocytes
  • pancreatic beta cells
42
Q

What types of cells typically exhibit rapid cellular turnover?

A
  • exposed to harsh environments or activities
  • skin cells, cells lining the gut lumen, and blood cells,
43
Q

Which types of cells generally do not undergo cellular turnover?

A

Highly specialized cells, such as photoreceptor cells in the eyes and auditory hair cells in the inner ear

44
Q

What does the level of cellular turnover depend on?

A

the tissue

45
Q

What kinds of cells have molecular turnover?

A

ALL CELLS

46
Q

What kinds of cells cannot be renewed?

A

often sensory cells with specilized architecture (once lost, cannot be replaced)
- photoreceptor cells
- auditory hair cells

47
Q

How does molecular turnover occur in non-renewable cells?

A

can still undergo molecular turnover by synthesizing new proteins and discarding old ones

48
Q

Describe the process of molecular turnover in photoreceptor cells.

A
  1. a “pulse” of radiolabeled leucine is added to photorecptor cells
  2. the labeled leucine is incorporated into new proteins in a new photoreceptive disc
  3. more new proteins are made and new discs move into the outer segment
  4. the labeled proteins are pushed up the outer segment
  5. at the end of their life, the labeled proteins are removied from the cell
49
Q

How can cell turnover occur in healthy cells?

A

it can be stem cell dependent or independent
- stem cells must be highly regulated by specific mechanisms

50
Q

What are some characteristics of stem cells?

A
  1. can divide indefinitely
  2. are not terminally differentiated
  3. can self-renew: child cell can remain a stem cell
  4. can differentitate: child cell can become a differentiated cell
51
Q

What happens the more a stem cell divides in a particular tissue?

A

the greater the risk of cancer in that tissue

52
Q

Why does stem cell divison and fate have to be carefully regulated?

A

to prevent cancer

53
Q

How do stem cells undergo division?

A

either asymmetric or symetric division

54
Q

How do internal factors influence stem cell fate?

A

specific cell fate determinants, are unevenly distributed during cell division, leading to different fates

55
Q

What are stem cell fate determinants?

A

specific proteins or molecules that influence the differentiation pathway of a stem cell, determining whether it remains a stem cell or differentiates into a specialized cell type

56
Q

What is symmetric division in the context of stem cells?

A

Both child cells inherit some stem cell fate determinant and both remain stem cells
- both can differentiate depending on external signals or internal factors

57
Q

What is asymmetric division in the context of stem cells?

A

onechild cell inherits all of the stem cell fate determinant and remains a stem cell
- other child differentitates

58
Q

How do environmental factors determine stem cell fate?

A

they are flexible: both child cells can take on the same fate if they experience the same environement

59
Q

What is a stem cell niche?

A

a specialized microenvironment that provides signals to stem cells

60
Q

How can stem cell niche interact with the stem cell?

A
  • secreted signal molecules
  • direct cell-cell contact
61
Q

What happens when the stem cell leaves the niche?

A

it becomes differentiated

62
Q

What is the significance of cell-cell contact in stem cell fate determination?

A
  • can influence whether a stem cell remains undifferentiated or differentiates
  • cells in contact with a stem cell niche receive signals that promote self-renewal, while those that lose contact tend to differentiate.
63
Q

Why is slow division important for stem cells?

A

can protect stem cells from:
- random mutations from DNA replication
- telomere depletion

64
Q

What are transit-amplifying cells, and how do they relate to stem cell division?

A
  • derived from stem cells
  • divide rapidly to increase cell numbers before final differentiation
65
Q

What are progenitor cells and how do they relate to stem cells?

A

descendants of stem cells that undergo stepwise differentiation, moving towards becoming terminally differentiated cells

66
Q

What are unipotent cells?

A

can produce only one cell type

67
Q

What are terminally differentiated cells?

A

fully differentiated and will not usually divid again

68
Q

Where are epidermal stem cells located?

A

in the basal layer of the epidermis (right above the basal lamina)

69
Q

Where is the stem-cell niche located for the epidermal stem cells?

A

basal lamina

70
Q

How and where do epidermal stem cells divide?

A

in the basal layer via symmetric divison

71
Q

What is the function of transit-amplifying cells in the epidermis?

A

they undergo many divisons from the stem cells and migrate into the prickle cell layer

72
Q

What happens once the arrive to the prickle-cell layer?

A

they differentiate further in the later layers and dead cells flake off from the surface

73
Q

What defines the differentiation pathway of blood stem cells?

A

A branched pathway that leads to increasingly specific cell fates as blood stem cells differentiate into committed progenitors and then terminally differentiated cells

74
Q

What is the role of transit-amplifying cells in blood cell differentiation?

A
  • multipotent hematopoietic progenitors
  • increase cell numbers before final differentiation and are crucial for the rapid production of blood cells
75
Q

How does the environment influence blood stem cell differentiation?

A

Signals in the environment can establish asymmetry that promotes specific branches of differentiation

76
Q

What is the relationship between stem cell self-renewal and differentiation?

A

Stem cells divide slowly to protect themselves, and their self-renewal is balanced with differentiation

77
Q

What is the purpose of transplantation experiments in identifying hematopoietic stem cells?

A

help determine whether certain cells can restore blood cell production in irradiated mice
- identifying multipotent hematopoietic stem cells

78
Q

What happens to mice that undergo x-irradiation?

A

halts blood cell production, leading to the mice’s inability to renew blood cells

79
Q

How many multipotent hematopoietic stem cells are estimated to be present in a sample of bone marrow?

A

only 1 in 100,000 cells

80
Q

What is the significance of transplanting a single multipotent stem cell into an irradiated mouse?

A

Transplanting just one multipotent stem cell can restore all types of blood cells, including the regeneration of stem cells (but we need 4-5 to save the mouse)

81
Q

What are the potential outcomes of injecting committed progenitor cells into an irradiated mouse?

A

may lead to the mouse living a short time but ultimately dying due to a decrease in blood cells

82
Q

What are embryonic stem (ES) cells?

A

pluripotent cells derived from the inner cell mass of a blastocyst, capable of differentiating into any adult cell type

83
Q

What type of cells have full developmental potential?

A

Embryonic stem (ES) cells

84
Q

What are some potential drawbacks of using embryonic stem cells?

A
  • ethical concerns
  • immune rejection
  • potential for cancer
85
Q

How can cultured embryonic stem cells be created without using a fertilized embryo?

A

can be generated through techniques like somatic cell nuclear transfer

86
Q

What is Somatic Cell Nuclear Transfer (SCNT)?

A

technique used to create a cloned embryo by transferring the nucleus of a somatic cell into an enucleated oocyte

87
Q

What are the key steps involved in SCNT?

A
  1. Enucleation: The nucleus is removed from an egg cell.
  2. Nuclear Transfer: The nucleus from a somatic cell is inserted into the enucleated egg.
  3. Activation: The egg is stimulated to begin dividing and developing into an embryo.
88
Q

What are induced pluripotent stem cells (iPS cells)?

A

a type of pluripotent stem cell that can be generated directly from adult cells by reprogramming them to an embryonic stem cell-like state

89
Q

How are iPS cells created from adult cells?

A

by introducing specific transcription factors (known as OSKM factors or Yamanaka factors) into adult cells

90
Q

What are the OSKM factors?

A
  • Klf4
  • Myc
  • Sox2
  • Oct4
91
Q

What kind of stem cells do almost all plant cells have?

A

totipotent

BIO230 Final (5 decks)

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