Developmental Biology Flashcards
(89 cards)
1
Q
Define Haploinsufficient
A
If one wild type copy is NOT sufficient for normal funciton
2
Q
Define Dominant negative
A
If the mutant copy produces a product that interferes with the wild type copy
3
Q
Define mutation
A
Any change in the sequence of genomic DNA
4
Q
Define Missense mutation
A
A mutation which results in a new codon (TTA-TCA)
5
Q
Define Nonsense mutation
A
A mutation which results in a stop codon (TTA-TAA)
6
Q
Define null/amorphic mutation
A
Complete loss of function
7
Q
Define hypomorphic mutation
A
Partial loss of wild type function (weak allele) i.e A missense mutation and temperature sensitive alleles
8
Q
Define Hypermorphic mutation
A
Over expression of a transcriptional unit
9
Q
Mutations in what gene cause Anaridia?
A
PAX6
10
Q
What is Anaridia?
A
Loss of iris
11
Q
Define development
A
A change in an organisms anatomy/morphology over time
12
Q
What is regional specification
A
The generation of pattern through the formation of a distinct body axis (anterior posterior, dorsal venral, left and right.)
13
Q
What is morphogenesis
A
Cell and tissue movements in the developing embryo
14
Q
What is the 32 cell stage of a developing embryo called?
A
Morula
15
Q
What is the name of the thick transparent membrane surrounding a mammalian egg?
A
Zona Pellucida
16
Q
What reaction happens straight after fertilization and how does this occur?
A
Cortical reaction. This occurs as there is an influx of calcium ions into the formed zygote. The influx initiates a range of metabolic processes such as the cortical reaction.
17
Q
What does the cortical reaction do?
A
Creates a sperm impermeable membrane around the newly formed zygote to prevent polyspermy.
18
Q
What is gastrulation?
A
An early embryological process in which the implanted blastula develops 3 distinct germ layers.
19
Q
What are the 3 germ layers?
A
Mesoderm, Ectoderm, Endoderm
20
Q
What does the Ectoderm give rise to?
A
Skin, CNS, PNS, neural crest, glia, pituitary gland
21
Q
What does the Endoderm give rise to?
A
Gut, digestive system, liver, thyroid, pancreas, bladder, thymus, yolk cells
22
Q
What does the Mesoderm give rise to?
A
Connective tissue, heart, blood, dermis, kidney, excretory system, reproductive system
23
Q
What is the name of the lining of the uterus?
A
Endometrium
24
Q
What is the name of the outer membrane of the blastocyst?
A
Tropoblast
25
What is the name of the cavity inside the blastula?
Blastocoel
26
What does the Hypoblast give rise to?
Mesoderm and umbilical vesicle
27
What does the Epiblast give rise to?
Ectoderm and amniotic cavity
28
What occurs during invagination of the zygote
The epiblast (ectoderm) layer invaginates up into the embryo forming the primitive streak.
29
What is mesenchyme?
A loosely organised, mainly mesodermal embryonic tissue which develops into connective and skeletal tissue, including blood and lymph
30
What forces drive cell and tissue rearrangements?
- Cell shape changes
- Changes in the expression of cell surface patterns
- localized cell proliferation
- localized cell death
31
Which germ layer forms the notochord?
Mesoderm
32
Which germ payer forms the Neural tube?
Ectoderm
33
How is the neural tube formed?
Notochord formation induces thickening of the ectoderm to form the neural plate, the central cells of the neural plate begin to move outwards forming the neural groove and neural folds. The folds continue to move outwards eventually connecting forming the neural tube.
34
Is the neural tube CNS or PNS?
CNS
35
Is the neural crest CNS or PNS?
PNS
36
What protein plays a vital role in muscle cell differentiation?
MyoD
37
Is MyoD sufficient or necessary for muscle cell differentiation? Justify your answer
Sufficient. Mice with a MyoD deficiency still develop skeletal tissue. This is because Myf5 acts redundantly with MyoD, mice without both Myf5 and MyoD lack skeletal muscle.
38
What are muscle stem cells named?
Satellite cells
39
What do stem cells give rise to in the skin?
Keratinocytes.
40
List ideal characteristics of the Frog (Xenopus) as a model organism
External fertilisation
Produces large batches of eggs
Robust
41
List ideal characteristics of the Chick as a model organism
They're accessible at most stages of development
Retroviral infection can be used to manipulate gene expression
large embryo
good representation of human.
42
What is cell fate?
What cells will normally become in development
43
A cell with a reversible commitment is described as being...
Specified
44
A cell with an irreversible commitment is described as being...
Determined
45
Two ways to test cell commitment
Culturing in Isolation
| Tissue Transplantation
46
How may cells does the nematode worm have?
959
47
What makes an Ideal cell marker?
Can be applied to any region at any stage.
Is readily visible.
Doesn't perturb normal development/ isn't toxic.
Doesn't leak into neighboring cells.
Isn't diluted by cell division.
Is inherited by all progeny of labelled cells.
48
What morphogen activated Hunchback (Hb)
Bicoid
49
What is the French Flag Model?
A framework indicating that morphogens can have a variety of different effects depending on whether their concentration achieves a threshold. I.e a low threshold will have produce a different effect than a high one.
50
What is induction?
Induction is signaling from one cell type to another, with a change in the specification of the responding cell/tissue.
51
What is competence?
The ability of a cell/tissue to respond to a signal (induction)
52
What are the 3 types of signalling between cells?
Diffusible signals; membrane bound receptors - growth factors.
Membrane bound signals; membrane bound receptors - Delta/Notch.
Diffusible signals; intracellular receptors - steroid hormones.
53
What is targetted transgenesis?
Incorporation of a foreign gene into a known gene of an organism.
54
What is a knockout gene?
When one gene of an organism is make inoperative.
55
Give an example of a complementary gene pair
Kit/Steel
56
What kind of receptor pair to Kit and Steel act as?
Ligand-pair receptor (kit codes for the receptor whilst steel codes for the binding factor)
57
What gene pathway gives rise to segment polarity in Drosophila?
Hedgehog (Hh)
58
What is recessive epistasis? And how is it useful?
When the phenotype of one mutation masks the effects of the other. And it can be used to determine the order that genes act in a pathway.
59
Explain the Hedgehog pathway of gene expression in determining wing expression in drosophila.
Hh is secreted as a signalling molecule. Hh binds to Patched (Ptc). Patch inhibits the activity of a second transmembrane protein, Smoothened (Smo). The binding of Hh to Ptc releives the repression of Smo leading to the activation of the transcription factor Ci. Ci now activates the transcription of 'wg' in the cells which have recieved the Hh signal.
60
What is an Allelic Series?
Different mutations in the same gene but result in different phenotypes.
61
What does complementary testing reveal?
It reveals mutants with very similar phenotypes that result from mutations in different genes. It allows us to suggest that these genes work in the same genetic pathway.
62
What cells have Kit receptors?
Melanoblasts. The Kit/Steel ligand receptor complex initiates the cell to produce Melanin. In mutations, the complex doesn't occur resulting in no pigmentation. (Piebaldism)
63
Describe the dorsal genetic pathway.
Spatzle is a ligand that binds to the Toll transmembrane receptor. Cactus is a cytoplasmic protein which binds to Dorsal in the cytoplasm preventing it from entering the nucleus. The activation of the Spatzle:Toll ligand-receptor complex allows the dissociation of Cactus from Dorsal. Dorsal now enters the nucleus to activate mesodorm generating genes, such as Twist.
Spatzle activates Toll inhibits cactus inhibits dorsal activates twist.
64
What is homeotic transformation?
When one structure is replaced by another. i.e antennapedia.
65
What is the function of Hox genes?
Hox genes specify segment identity in all animals with a segmented body plan.
66
What is the Ubx gene mutation described as and what does it do?
It is described as being a homeotic transformation gene. The Ubx gene mutation transforms the third thoracic segment (Haltere) into the characteristics of the second thoracic segment (wings)
67
What complex are the Ubx, Abd-B and Abd-A genes involved in?
Bithorax complex (BX-C)
68
What is a homeobox?
A highly conserved 180 nucleotide sequence.
69
What does a Limb bud consist of?
A mound a mesenchymal cells surrounded by a jacket of epithelium (ectodermal)
70
What three regions are distinguished in a limb bud?
Apical Ectodermal ridge (AER)
Progress Zone (PZ)
Zone of Polarizing Activity (ZPA)
71
What is the role of the Apical Ectodermal Ridge?
To maintain cell proliforation and survival in PZ
72
What is the role of the Progress zone?
To determine cells fate.
73
What is the role of the Zone of Polarizing activity?
To act as an organizing centre to pattern the AP axis of the limb.
74
Where is Sonic Hedgehog (Shh) expressed?
Zone of Polerising activity - Limb bud
75
What is a proneural cluster?
A cluster of cells in the embryo containing an equivelance group: each having the potential to become a neuron. Only one cell is singled out to become a neuron, this is achieved through Lateral Inhibition.
76
What is lateral inhibition mediated by in neuron development and how is this achieved.
Mediated by Delta/Notch. Delta is a transmembrane ligand that activates Notch. This leads to the cleavage of Notch and the release of an intracellular fragment that forms part of a transcription factor complex. Feedbaclk loops in the equivelance group allow one cell to be singled out and become a Neuroblast. The rest of the cells then recieve a higher concentration of Notch so they're inhibited from becoming neuroblasts.
77
Describe the assymetric division of neuroblasts
Neuroblasts delaminate from the neurectoderm and undergo assymetric division to form a Ganglion Mother Cell and another neuroblast.
78
What fraction of the embryo forms the CNS?
Neurectoderm (found on the ventral side of the embryo)`
79
Define Totipotency
Potential to form the entire body (i.e zygote)
80
Define Pluripotent
Cell retains potential to become multpile cell types
81
Define multipotent
Potential to become any fell type in the body
82
Define bipotent
Can form two different cell types
83
Define Unipotent
Can form one cell type.
84
What is a hetrokaryon?
A cell made of two different genotypes.
85
What defect occurs when Sonic Hedgehog becomes inactive?
Holoprosencephaly - when the prosencephalon fails to develop into two hemispheres.
86
Mutations in the Hh pathway can lead to limb defects, what is the medical term for this?
Polydactyly.
87
How does Cyclopamine inhibit the SHh signalling pathway?
It is a potent teratogen and acts as an antagonist so Smo, thus inhibiting Smo resulting in a loss of function of Shh
88
What is the Shh signalling pathway? Ptc Smo and Gli
Shh binds to Ptc, (Ptc usually inhibits Smo) As Shh binds to Ptc, Ptc becomes inhibited, allowing Smo to be stimulated. Smo releases Gli which then enters the nucleus and acts as a transcrpition factor.
89
Where is Sonic hedgehog expressed?
Along the midline of the embryo (notochord and floorplate) and in the Zone of Polarizing activity.
