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Cells to Organisms > Differentiation > Flashcards

Differentiation Flashcards

1
Q

What is meant by “terminal differentiation”?

A

the final cell form
cell can no longer differentiate into a more specialised form

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2
Q

What is meant by “developmental potency”?

A

how many different options a cell has to differentiate into

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3
Q

What are the three main areas of the germ layer?

A

ectoderm
mesoderm
endoderm

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4
Q

What cells can the ectoderm become?

A

the central nervous system: retina, photoreceptors, neurons
skin, hair and sweat glands

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5
Q

What cells can the mesoderm become?

A

bone
muscle: skeletal, cardiac (heart), smooth
kidney
connective tissue

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6
Q

What cells can the endoderm become?

A

liver
gut
lungs
pancreas: exocrine cells, endocrine cells

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7
Q

When are the germ layers formed?

A

during gastrulation, usually 14-21 days after fertilisation

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8
Q

What is meant by gene constancy?

A

the fact that all cells have all genes, just some are in an inactive state

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9
Q

What is a TATA box?

A

a DNA signal that binds the TATA-binding protein TFIID, a transcription factor

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10
Q

What is a helper protein?

A

a protein that directs RNA polymerase to gene transcription start sites
control where transcription starts not when gene is transcribed
used by all gene sequences transcribed by DNA polymerase II

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11
Q

What are the signal sequences next to genes to which transcription factors bind to?

A

enhancers

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12
Q

What ways can transcription factors recruit RNA polymerase to the TATA box

A
  1. direct recruitment
  2. indirect recruitment by altering chromatin structure
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13
Q

What proteins are recruited by TFs to alter chromatin structure?

A
  1. histone acetyl transferase (HAT)
    - acetylation loosens histone interactions w DNA making the gene more accessible
  2. chromatin remodelling complex

in each case these chromatin-modifying enzymes promote rna polymerase binding and function

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14
Q

What does a gene’s transcriptional activity depend on?

A
  1. what binding sites are in its DNA enhancer sequence
    AND
  2. whether the appropriate (cognate) TFs are present in cell
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15
Q

What is MyoD?

A

a transcription factor that activates expression of 100s of genes required for muscle differentiation including myosin II

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16
Q

What is the structure of MyoD?

A

binds to DNA as a dimer
has a basic-helix-loop-helix (bHLH) domain
its recognition sequence on genes is known as an E box

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17
Q

What is the result of transfecting a cell with a plasmid containing the MyoD gene?

A

can force the cell to become a muscle cell

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18
Q

What are plant trichomes?

A

small spikes on plant leaves that are spaced evenly

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19
Q

What are some benefits to plant trichomes?

A

deters insects, breaks up wind currents, reduces sun exposure

20
Q

How do TF repressors prevent transcription?

A
  1. prevent binding of activators
  2. recruit proteins that tighten chromatin, making the gene less accessible
21
Q

What is a feature of the GATA1 TF structure?

A

zinc-finger

22
Q

What sequence does GATA1 bind to?

A

A/T -GATA-A/G

23
Q

What are GATA1s target genes?

A

alpha and beta globin genes
erythropoietin receptor
heam biosynthesis enzymes
spectrin

24
Q

What conditions have to be met to activate the beta-globin gene?

A

GATA1 and CP1 and NF1 have to be bound (present in erythroblasts)
beta globin encodes for the heamoglobin subunits

25
Q

GATA1 is expressed in several blood lineages but only activate globin genes in which blood cell?

A

erythroblasts
thanks to CP1 and NF1

26
Q

What is a common modification made to transcription factors and how does it affect them?

A

phosphorylation
negative charge causes a conformational change
regulated via a kinase enzyme

27
Q

What is a GRN?

A

Gene Regulatory Network
a set of genes, or parts of genes, that interact with each other to control a specific cell function

28
Q

How do growth factors promote cell proliferation?

A

activate a protein cascade
mitogen activated protein kinase enters the nucleus and phosphorylates transcription factors

29
Q

What is EGF and how does it work?

A

epidermal growth factor is a mitogen
binding to egf receptors leads to phosphorylation of MYC, a bHLH-LZ (leucine zipper) TF which drives transcription of cyclin genes

30
Q

Where is MYC phosphorylated on the EGF cell proliferation pathway?

A

on several serine and threonine residues (importantly ser-62)

31
Q

How does erythropoietin (EPO) induce red blood cell differentiation?

A

secreted from the kidney
causes phosphorylation of GATA1 increasing its DNA binding affinity

32
Q

What are transcription factors regulated by?

A

other transcription factors, and kinases

33
Q

What are transcription factors important for with regards to differentiation?

A

orderly progression through to differentiation
control of cell fate choices

34
Q

What 3 transcription factors are involved in the differentiation in sequential steps of guard cell specialisation?

A
  1. speechless (SPCH)
  2. mute
  3. Fama
35
Q

What are somites?

A

populations of precursors cells that eventually give rise to important structures

36
Q

What is Pax3?

A

a ‘paired box’ homeodomain TF expressed in somite involved in muscle cell differentiation

37
Q

What are the closely related bHLH TFs involved in muscle cell differentiation?

A

MyoD
Myf5
Mrf4
Myogenin

38
Q

What TFs are involved in MyoD gene regulation?

A

Pax3 and signal-activated Myf5, both have to be present

39
Q

After the MyoD gene is activated it activates its own expression, what is this known as?

A

positive autoregulation

40
Q

What signal activates Myf5?

A

Wnt

41
Q

How are MyoD and Myf5 eventually degraded and why?

A

cyclin-dependent kinases phosphorylate them, targeting them for proteolytic degradation
this stops muscle differentiation allowing for enhancement of myoblast proliferation

42
Q

How is Pax3 degraded and why?

A

it is only required for early muscle development and must be degraded for later stages to proceed
its mRNA is degraded by RNA interface, specifically regulatory RNA named microRNA miR-1

43
Q

What TF controls the determination of the ‘eye primordium’ triggering the whole process of eye development?

A

PAX6

44
Q

How is the cell fate of a myeloid progenitor decided?

A

antagonistic interaction between GATA1 and PU.1 TFs
autoregulate to try and boost themselves above the other

45
Q

How does PU.1 repress GATA1?

A

can bind to GATA1 as its bound to the GATA1 gene and knock off a coactivator protein
the recruits a chromatin methylation protein which tightens chromatin making the GATA1 gene less accessible

46
Q

What is the role of cdx2?

A

gives gut cells the potential to become pre-pancreatic cells
does this by activating pdx1 expression only if fgf2 signal is received from contact with the notochord

47
Q

What is one way of triggering differentiation in myoblasts?

A

Removing growth factors to stop proliferation.

Cells to Organisms (8 decks)

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