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Biomedical Science > Developmental Biology > Flashcards

Developmental Biology Flashcards

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Biology 101 flashcards
1
Q

Define Haploinsufficient

A

If one wild type copy is NOT sufficient for normal funciton

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2
Q

Define Dominant negative

A

If the mutant copy produces a product that interferes with the wild type copy

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3
Q

Define mutation

A

Any change in the sequence of genomic DNA

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4
Q

Define Missense mutation

A

A mutation which results in a new codon (TTA-TCA)

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5
Q

Define Nonsense mutation

A

A mutation which results in a stop codon (TTA-TAA)

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6
Q

Define null/amorphic mutation

A

Complete loss of function

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7
Q

Define hypomorphic mutation

A

Partial loss of wild type function (weak allele) i.e A missense mutation and temperature sensitive alleles

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8
Q

Define Hypermorphic mutation

A

Over expression of a transcriptional unit

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9
Q

Mutations in what gene cause Anaridia?

A

PAX6

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10
Q

What is Anaridia?

A

Loss of iris

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11
Q

Define development

A

A change in an organisms anatomy/morphology over time

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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.)

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13
Q

What is morphogenesis

A

Cell and tissue movements in the developing embryo

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14
Q

What is the 32 cell stage of a developing embryo called?

A

Morula

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15
Q

What is the name of the thick transparent membrane surrounding a mammalian egg?

A

Zona Pellucida

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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.

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17
Q

What does the cortical reaction do?

A

Creates a sperm impermeable membrane around the newly formed zygote to prevent polyspermy.

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18
Q

What is gastrulation?

A

An early embryological process in which the implanted blastula develops 3 distinct germ layers.

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19
Q

What are the 3 germ layers?

A

Mesoderm, Ectoderm, Endoderm

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20
Q

What does the Ectoderm give rise to?

A

Skin, CNS, PNS, neural crest, glia, pituitary gland

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21
Q

What does the Endoderm give rise to?

A

Gut, digestive system, liver, thyroid, pancreas, bladder, thymus, yolk cells

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22
Q

What does the Mesoderm give rise to?

A

Connective tissue, heart, blood, dermis, kidney, excretory system, reproductive system

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23
Q

What is the name of the lining of the uterus?

A

Endometrium

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24
Q

What is the name of the outer membrane of the blastocyst?

A

Tropoblast

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25
Q

What is the name of the cavity inside the blastula?

A

Blastocoel

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26
Q

What does the Hypoblast give rise to?

A

Mesoderm and umbilical vesicle

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27
Q

What does the Epiblast give rise to?

A

Ectoderm and amniotic cavity

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28
Q

What occurs during invagination of the zygote

A

The epiblast (ectoderm) layer invaginates up into the embryo forming the primitive streak.

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29
Q

What is mesenchyme?

A

A loosely organised, mainly mesodermal embryonic tissue which develops into connective and skeletal tissue, including blood and lymph

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30
Q

What forces drive cell and tissue rearrangements?

A
  • Cell shape changes
  • Changes in the expression of cell surface patterns
  • localized cell proliferation
  • localized cell death
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31
Q

Which germ layer forms the notochord?

A

Mesoderm

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32
Q

Which germ payer forms the Neural tube?

A

Ectoderm

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33
Q

How is the neural tube formed?

A

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.

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34
Q

Is the neural tube CNS or PNS?

A

CNS

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35
Q

Is the neural crest CNS or PNS?

A

PNS

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36
Q

What protein plays a vital role in muscle cell differentiation?

A

MyoD

37
Q

Is MyoD sufficient or necessary for muscle cell differentiation? Justify your answer

A

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
Q

What are muscle stem cells named?

A

Satellite cells

39
Q

What do stem cells give rise to in the skin?

A

Keratinocytes.

40
Q

List ideal characteristics of the Frog (Xenopus) as a model organism

A

External fertilisation
Produces large batches of eggs
Robust

41
Q

List ideal characteristics of the Chick as a model organism

A

They’re accessible at most stages of development
Retroviral infection can be used to manipulate gene expression
large embryo
good representation of human.

42
Q

What is cell fate?

A

What cells will normally become in development

43
Q

A cell with a reversible commitment is described as being…

A

Specified

44
Q

A cell with an irreversible commitment is described as being…

A

Determined

45
Q

Two ways to test cell commitment

A

Culturing in Isolation

Tissue Transplantation

46
Q

How may cells does the nematode worm have?

A

959

47
Q

What makes an Ideal cell marker?

A

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
Q

What morphogen activated Hunchback (Hb)

A

Bicoid

49
Q

What is the French Flag Model?

A

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
Q

What is induction?

A

Induction is signaling from one cell type to another, with a change in the specification of the responding cell/tissue.

51
Q

What is competence?

A

The ability of a cell/tissue to respond to a signal (induction)

52
Q

What are the 3 types of signalling between cells?

A

Diffusible signals; membrane bound receptors - growth factors.
Membrane bound signals; membrane bound receptors - Delta/Notch.
Diffusible signals; intracellular receptors - steroid hormones.

53
Q

What is targetted transgenesis?

A

Incorporation of a foreign gene into a known gene of an organism.

54
Q

What is a knockout gene?

A

When one gene of an organism is make inoperative.

55
Q

Give an example of a complementary gene pair

A

Kit/Steel

56
Q

What kind of receptor pair to Kit and Steel act as?

A

Ligand-pair receptor (kit codes for the receptor whilst steel codes for the binding factor)

57
Q

What gene pathway gives rise to segment polarity in Drosophila?

A

Hedgehog (Hh)

58
Q

What is recessive epistasis? And how is it useful?

A

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
Q

Explain the Hedgehog pathway of gene expression in determining wing expression in drosophila.

A

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
Q

What is an Allelic Series?

A

Different mutations in the same gene but result in different phenotypes.

61
Q

What does complementary testing reveal?

A

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
Q

What cells have Kit receptors?

A

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
Q

Describe the dorsal genetic pathway.

A

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
Q

What is homeotic transformation?

A

When one structure is replaced by another. i.e antennapedia.

65
Q

What is the function of Hox genes?

A

Hox genes specify segment identity in all animals with a segmented body plan.

66
Q

What is the Ubx gene mutation described as and what does it do?

A

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
Q

What complex are the Ubx, Abd-B and Abd-A genes involved in?

A

Bithorax complex (BX-C)

68
Q

What is a homeobox?

A

A highly conserved 180 nucleotide sequence.

69
Q

What does a Limb bud consist of?

A

A mound a mesenchymal cells surrounded by a jacket of epithelium (ectodermal)

70
Q

What three regions are distinguished in a limb bud?

A

Apical Ectodermal ridge (AER)
Progress Zone (PZ)
Zone of Polarizing Activity (ZPA)

71
Q

What is the role of the Apical Ectodermal Ridge?

A

To maintain cell proliforation and survival in PZ

72
Q

What is the role of the Progress zone?

A

To determine cells fate.

73
Q

What is the role of the Zone of Polarizing activity?

A

To act as an organizing centre to pattern the AP axis of the limb.

74
Q

Where is Sonic Hedgehog (Shh) expressed?

A

Zone of Polerising activity - Limb bud

75
Q

What is a proneural cluster?

A

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
Q

What is lateral inhibition mediated by in neuron development and how is this achieved.

A

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
Q

Describe the assymetric division of neuroblasts

A

Neuroblasts delaminate from the neurectoderm and undergo assymetric division to form a Ganglion Mother Cell and another neuroblast.

78
Q

What fraction of the embryo forms the CNS?

A

Neurectoderm (found on the ventral side of the embryo)`

79
Q

Define Totipotency

A

Potential to form the entire body (i.e zygote)

80
Q

Define Pluripotent

A

Cell retains potential to become multpile cell types

81
Q

Define multipotent

A

Potential to become any fell type in the body

82
Q

Define bipotent

A

Can form two different cell types

83
Q

Define Unipotent

A

Can form one cell type.

84
Q

What is a hetrokaryon?

A

A cell made of two different genotypes.

85
Q

What defect occurs when Sonic Hedgehog becomes inactive?

A

Holoprosencephaly - when the prosencephalon fails to develop into two hemispheres.

86
Q

Mutations in the Hh pathway can lead to limb defects, what is the medical term for this?

A

Polydactyly.

87
Q

How does Cyclopamine inhibit the SHh signalling pathway?

A

It is a potent teratogen and acts as an antagonist so Smo, thus inhibiting Smo resulting in a loss of function of Shh

88
Q

What is the Shh signalling pathway? Ptc Smo and Gli

A

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
Q

Where is Sonic hedgehog expressed?

A

Along the midline of the embryo (notochord and floorplate) and in the Zone of Polarizing activity.

Biomedical Science (8 decks)

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