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Developmental, stem cell and regenerative biology > Vertebrates > Flashcards

Vertebrates Flashcards

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1
Q

what is meant by cell ‘fate’?

A

cells have a fate, this means the thing that it is destined to become after differentiation e.g. a cell can be fated to be a muscle cell

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2
Q

what determines a cell’s fate?

A

their location within a mass of cells after fertilisation and proliferation

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3
Q

what is the lineage tracing technique in cell fate maps?

A

cells are named according to their position and injected with coloured dyes, they are left for a few days and then analysed to identify which cells move where

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4
Q

what does it mean if a cell is committed to its fate and what is it determined by?

A

it will give rise to the same cell type no matter where it is located
its fate is determined by intrinsic factors such as transcription factor

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5
Q

what does it mean if a cell’s fate is changeable and what is it controlled by?

A

it will give rise to a different cell type if it changes position
it can be reprogrammed and is controlled by signals that tell it to move locations

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6
Q

what is an ectopic signalling source?

A

a cell that induces the fate of other cells by releasing signals

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7
Q

what is experimental embryology?

A

experiments that involve the physical manipulation of the embryo

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8
Q

what are competent or receptive cells?

A

cells that express a specific receptor that receives a signal from another cell

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9
Q

what are permissive signals?

A

signals that allow or block cells from responding to other signals

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10
Q

what are chemo attractants?

A

signals that attract or repulse cells during migration

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11
Q

what are patterning cells?

A

identical cells that adopt different cell fates when stimulated by a signal

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12
Q

how is RNA in situ hybridisation used to analyse gene expression?

A

stains cells blue/purple to show if they express the RNA for a certain gene

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13
Q

how are antibodies used to analyse gene expression?

A

uses antibodies to detect where specific proteins are expressed in a cell and where they are located

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14
Q

what are the advantages and disadvantages of using zebra fish models?

A

advantages: vertebrate, large batches of embryos, relatively transparent, external fertilisation
disadvantages: complex genome with gene duplication, not inbred so high variation

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15
Q

what are the advantages and disadvantages of using mice models?

A

advantages: mammal, rapid generation time (8 weeks), inbred strains so low variability
disadvantages: internal embryos so poor access, small batches of embryos, expensive, ethical issues

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16
Q

what are the advantages and disadvantages of using frog models?

A

advantages: external fertilisation, large batches of embryos, large embryos and cells
disadvantages: long generation time (1+ year), yolky embryo so not transparent

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17
Q

what are the advantages and disadvantages of using chick models?

A

advantages: big embryo, tetrapod
disadvantages: not accessible early, limited genetics

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18
Q

what most an organism have to be classed as a vertebrate?

A

a vertebral column which protects the neural tube
a cranium (skull) that protects the brain
an endoskeleton

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19
Q

what is the conserved stage in early embryonic development?

A

the pharyngula stage
an embryo that has 5 pharyngeal pouches (which give rise to gills in fish) and somites (repeated structures called metameric structures down the trunk which form segments)

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20
Q

why is the pharyngula stage conserved in vertebrates?

A

due to a bottle-neck during development that is evolutionarily conserved because any mutations during early development of the embryo would cause it to be destroyed

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21
Q

what happens during early development in vertebrates?

A
  1. oocyte is fertilised with sperm
  2. maternal and paternal nuclei fuse to form zygote
  3. cleavages of the zygote form blastomeres
  4. blastula forms with blastomeres on the outside and the blastocoel on the inside
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22
Q

what causes the start of cell division in the early embryo?

A
  1. calcium ions are released from the mitochondria and move in a wave across the oocyte
  2. the calcium ions act on proteins that control the cell cycle and cleavage
  3. with each round of cell division there is a burst of calcium ions to synchronise it
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23
Q

what is unique about the cell cycle in early embryos?

A

there is only M phase, cytokinesis and S phase and no G1 or G2 phases
this means that RNA and proteins aren’t made because transcription happens in G1

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24
Q

how do embryos overcome the lack of G1 and G2 phase?

A

using maternal stores containing RNA and protein to provide the building blocks to make DNA

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25
what happens when maternal stores in the early embryo run out?
the zygotic genome must be activated to produce its own RNA, when activated the cell cycle slows, loses its ability to divide rapidly and cells start to move around (gastrulation)
26
what is gastrulation?
the movement of cells to the inside of the embryo to form the endoderm and mesoderm layers, cells that remain on the surface form the ectoderm the cells are specified into the layers and their cell fate becomes restricted
27
what cells are derived from each layer of the embryo?
neurons, glia, epidermis and pigment cells are derived from the ectoderm cells muscle, cartilage and bone, dermis, kidney, heart and blood are derived from the mesoderm cells lungs and the gut are derived from endoderm cells
28
what is the process of gastrulation?
1. a small pore called blastopore forms and cells change shape 2. cells move inside the pore and spread around to form a circular shape 3. some cells move up to form the anterior and posterior and the ectoderm moves around outside to encase the embryo
29
what are the features of the epithelial cells that arise from gastrulation?
highly structured usually cuboidal joined together by junctional complexes
30
what are the features of the mesenchymal cells that arise from gastrulation?
move around easily (because they are separated by extracellular matrix proteins) amorphous (no defined shape)
31
what is morphogenesis?
changing the shape of an embryo or part of an embryo
32
what can cause morphogenesis?
cytoskeletal rearrangements which change the shape of the cell cell adhesion molecules that can hold cells together or repel them apart cell migration that changes tissue shape localised cell proliferation which can cause elongation of limbs cell death that causes tissue shape to change
33
what are somites?
temporary structures that form in the embryo and disintegrate when they have formed they become specified to form cells of the dermis, vertebral column and skeletal muscles
34
what is somitogenesis?
when somite cells form anterior to posterior after gastrulation
35
how does segmentation happen?
mesenchymal cells gather together dorsally and cells on the outside edge of the somite epithelialize to make it distinct from neighbouring tissue the somites then disassemble and revert to mesenchymal cells one somite gives rise to one vertebrae for segmentation but they will form the posterior of one vertebrae and the anterior of the adjacent vertebrae
36
what is dermomyotome?
a sheet of tissue that develops from the dorsal part of the somite and forms the dermis and skeletal muscle
37
what is the sclerotome?
a sheet of tissue that develops from the ventral part of the somite and forms vertebrae and ribs (bones)
38
what is neurulation?
formation of the neural tube (brain and spinal cord) from the ectoderm as it invaginates and folds up to join across the top down the posterior side
39
why are chicks the best model organism for limb development in vertebrates?
they share the same homologous skeletal features and have probably evolved from a common ancestor to us they go through the same stages of development as us
40
what are the 3 distinct regions in the limb bud?
the AER in the ectoderm the progress zone and differentiating tissues in the mesoderm
41
what is the AER and how does it form?
the apical ectodermal ridge formed from epithelial cells bunching up
42
what is the progress zone and what happens when cells exit it?
an area containing proliferating mesenchymal cells that allows the limb to elongate as cells exit the progress zone they differentiate into different tissues
43
what is the role of the AER?
it controls growth and elongation of the limb bud and establishes the proximal-distal axis of the limb it does this by secreting growth factors (fgfs) into the proximal zone
44
what is the role of the progress zone?
it tells which cells to develop in the limb
45
what are fgf4 and fgf8 genes and how are they expressed?
fibroblast growth factors secreted by the AER there are 22 fgfs in mice but 4 and 8 are the most important they are expressed strongly in overlapping expression domains
46
what is the role of fgf4 and fgf8 genes?
they are both required for limb development but they are redundants
47
what is the ZPA and what is its role in limb development?
zone of polarising activity formed from mesenchymal cells it polarises the tissue to form the anterior-posterior axis by secreting a signal this is known as patterning identity
48
what controls digit formation?
there is a signal that diffuses out from the posterior end of the digit and establishes a concentration gradient to give different fates to cells at different concentrations
49
what is sonic the hedgehog?
SHH is a secreted ligand that is needed for the anterior-posterior axis formation
50
what was observed in mice with SHH mutations?
they had no limb defects but the limbs were mirrored like the ZPA mutants
51
what is the transcriptome?
all the genes that are actively transcribed from RNA
52
what does differential gene expression mean?
cells with different expression profiles
53
what are transcription factors?
proteins that interact with the major groove on the DNA backbone to form hydrogen bonds they bind to the regulatory element but the bond formed is unstable so falls off easily
54
what are the 2 types of regulatory elements?
enhancers which are binding sites for transcriptional activators silencers which are binding sites for transcriptional repressors
55
what is MyoD?
a transcription factor that is expressed only in muscle precursors and muscle cells it controls the expression of genes for muscle differentiation and can maintain its own expression through a positive feedback loop it is redundant with the gene Myf5
56
what is the process of muscle differentiation?
1. muscle precursors in somites receive signals such as the transcription factor mrf4 2. this activated MyoD and myf5 and causes myoblasts to form 3. growth factors can repress differentiation but if they aren't present myoblasts start to express myogenin 3. this causes muscle cells to fuse together forming a muscle fibre and other genes such as myosin II to be expressed
57
what are satellite stem cells?
stem cells that line muscle fibres but aren't differentiated into muscle cells yet when stimulated by signals the they divide and differentiate into muscle cells
58
how are genes always written?
in all italics
59
what are germline and somatic mutations?
germline are inherited mutations carried in oocytes or sperm somatic are random mutations that aren't passed on to offspring
60
how are forward genetics used in labs?
inducing random mutations in model organisms (mutagenesis) then cross them and analyse the phenotype to see what gene causes it
61
how are reverse genetics (gene knockout) used in a lab?
the endogenous gene (gene inside the animal) is taken and removed or mutated the phenotype is analysed to find the gene function
62
how is CRISPR used in labs?
to knock in or out a gene and it can be used in any organism
63
how do mutations that change regulatory sequences affect genes?
changes the binding site for transcription factors on DNA leading to reduced expression of a gene and production of a protein
64
how do mutations that change non-coding sequences affect genes?
changes to introns can affect RNA splicing, stability or translation so less protein is produced
65
how do mutations that change coding sequences affect genes?
changes in DNA that alters the amino acid sequence of a protein affects how it is folded it could lose its function, or create a premature stop codon leading to a truncated protein
66
what are the 3 functional groups of transcription factors and their roles?
a DNA-binding domain: where DNA binds a dimerization domain: where dimers are formed from 2 identical proteins a domain that regulates interactions
67
how are transcription factors activated?
the proteins dimerise and there is a conformational change causing it to be activated
68
what is a missense and nonsense mutation?
a missense mutation where a single amino acid is substituted a nonsense mutation is a mutation that creates a premature stop codon
69
what is an amorphic mutation?
a missense mutation that inactivates the DNA binding domain of a transcription factor
70
how do amorphic mutations affect heterozygous and homozygous animals?
in heterozygous animals the gene is redundant so there transcriptional activity from the wild-type allel (haplosufficiency) in homozygous animals (with 2 mutated alleles) there will be no transcriptional activation, this is recessive
71
what is a hypomorphic mutation?
a missense mutation in the DNA binding domain causing its activity to be weakened
72
how do hypomorphic mutations affect heterozygous and homozygous animals?
in heterozygous animals there is no mutant phenotype as there is enough product from the wild-type allele in homozygous animals there is a milder phenotype due to poor transcriptional activation, the dimer forms on DNA but often falls off, this is recessive
73
what is an antimorphic mutation?
a missense mutation that destroys the dimerization domain
74
how do antimorphic mutations affect heterozygous and homozygous animals?
the heterozygote has a mutant form that binds to DNA but doesn't dimerise to the wild-type so it doesn't go through a conformational change and doesn't become activated, however it still has some function but transcription is compromised and will only be activated if two wild-type proteins dimerise which is dominant in the homozygote it is completely inactivated and there is no transcription
75
what is a hypermorphic mutation?
a missense mutation that causes the transcription factor to be activated without dimerisation
76
how do hypermorphic mutations affect heterozygous and homozygous animals?
in the heterozygote the mutant form binds to DNA and is active all the time (this is called constitutively active), this increases the overall activation of transcription and it is dominant the homozygote is the same as the heterozygote
77
which mutations are loss-of-function and what are their phenotypes?
amorphic (recessive) hypomorphic (recessive) antimorphic (dominant)
78
which mutation if gain-of-function and what is its phenotype?
hypermorphic (dominant)
79
what are alleles?
different forms of a gene
80
what are reporter constructs used for and how do they work?
help us to study the activity of genes, cells or tissues in vivo they use green fluorescent protein (GFP) proteins absorb different wavelengths of light and emit them at a different wavelength to produce a fluorescent colour
81
how do you produce a reporter construct for GFP transgenic lines?
remove exons and insert the GFP in place of the protein reintroduce the gene into the animal this won't tell us where the protein is localised only which cells express the protein
82
how do you produce a fusion gene for GFP transgenic lines?
add the GFP sequence to the last exon of the DNA delete the stop codon so GFP is translated at the end of the protein reintroduce the gene into the animal usually the normal gene won't be removed so there will be two copies of the gene
83
what are the 2 uses for GFP transgenic lines?
to follow the expression of a gene or to follow the behaviour of cells in vivo to follow subcellular localisation of a protein

Developmental, stem cell and regenerative biology (3 decks)

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