Karteikarten
Developmental Biology
Karten in diesem Stapel (79)
- 1What is a Zygote?Fertilised ovum that contains totipotent cells
- 2How is an unequal daughter cell produced?Cleavage divisions can set up asymmetries by segregating determinants.
- 3What are germ cell determinants?Specific proteins or mRNA that determine which cells will become germ cells.
- 4What is Pattern Formation?The process by which a spatial and temporal pattern of cellular activities is organised within the embryo so that a well-ordered structure develops. Involves allocation of different germ layers.
- 5What are the three germ layers and where are they found in the human body?Endoderm - gut, liver and lungs
Mesoderm - skeleton, muscle, kidney, heart and blood
Ectoderm - Epidermis of skin, nervous system - 6Where are the three layers found in insects?Endoderm - gut
Mesoderm - muscle, heart, blood
Ectoderm - cuticle, nervous system - 7What is regional specification?Cells ability to 'know' where they are and differentiate accordingly
- 8Give some examples of the forms of positional informationInherited cytoplasmic determinants
Short or long-range signals - 9What processes are involved in morphogenesis?Differential proliferation
Change in cell shape and size
Cell movement
Cell fusion
Cell death - 10What is Gastrulation?Moves the germ layers relative to one another
- 11What is progressive cell commitment?Early embryonic cells are pluripotent but their potential gradually becomes restricted due to differentiation. When cells are allocated a germ layer, they are no longer totipotent. Differentiation is most often irreversible.
- 12What is a Blastomere?A cell formed by cleavage of a fertilised ovum
- 13What is a morula?A solid ball of cells resulting from division of a fertilised ovum, and from which a blastula is formed.There is increased cell-cell adhesion and tight junctions.
- 14What is E-cadherin?A transmembrane protein that becomes restricted to regions of intercellular contact to maximise blastomere contact. It also binds to other E-cadherin molecules.
- 15What cells form the inner cell mass?Non-polarised cells which communicate through gap junctions
- 16What does tangential cleavage produce?Polarised and non-polarised cells
- 17What does radial cleavage produce?Two polarised cells
- 18What is the blastocyst?A structure formed in the early development of mammals. It possesses an inner cell mass (ICM) which subsequently forms the embryo. The outer layer of the blastocyst consists of cells collectively called the trophoblast.
- 19What is the first differentiation event in embryonic development?The segregation of trophectoderm and inner cell mass lineages.
- 20What does cell fate depend on?Relative position
- 21What does the inner cell mass give rise to?Embryo proper and some extra-embryonic tissue
- 22What does the trophectoderm give rise to?Extra embryonic tissue
- 23What is the Blastocoel?Fluid-filled blastocyst cavity
- 24What does the zona pellucida present?Implantation in the oviduct
- 25What does active transport of sodium ions into the blastocoel lead to?Fluid accumulation.
As the sodium enters the cell, water diffuses into the cell by osmosis. The resulting hydrostatic pressure inflates the blastocoel. - 26What is the trophoblast?Cells forming the outer layer of a blastocyst, which provide nutrients to the embryo and develop into a large part of the placenta.
- 27What is the Hypoblast?Forms from the inner cell mass
- 28What is the Epiblast?Derived from the inner cell mass and lies above the hypoblast. The epiblast gives rise to the three primary germ layers.
- 29How does implantation occur?Trophoblast cells express integrin proteins which interact with ECM proteins expressed by the epithelial cells of the uterine mucosa.
Integrin-laminin interations promote attachment.
Integrin-fibronectin interactions promote migration.
Theses interactions anchor the embryo into the uterus wall. - 30What does the epiblast form?Embryo proper
- 31What does the hypoblast form?Extra embryonic tissue
- 32Describe the structure of the epiblastColumnar cells adjacent to the blastocyst cavity
- 33Describe the structure of the hypoblastSmall cuboidal cells adjacent to the blastocyst cavity
- 34What is the primitive streak?The faint streak which is the earliest trace of the embryo in the fertilized ovum of a higher vertebrate. It forms on the surface of the epiblast after two weeks in the region that will become the posterior of the embryo. This is the first sign of the anteroposterior axis. During gastrulation, epiblast cells migrate towards the primitive streak and invaginate, displacing the hypoblast. This eventually forms the three germ layers.
- 35What is neurulation?The ectoderm folds along its central axis to form the neural tube. The neural folds elevate and fuse. Neural crest cells form near the site of fusion and migrate away to give rise to heart valves. The epidermis fuses above the neural tube. This process forms the spinal cord.
1. Neural plate
2. Neural folds
3. Neural tube - 36What are somites and how are they formed?Paired structures - one either side of the midline. They form a sequence in the anterior to posterior direction. They are formed by paraxial mesoderm segmenting into somites.
- 37What does the endoderm give rise to?The endoderm ins internalised and gives rise to the epithelial lining of the GI tract. Also, provides the lining of the stomach, liver, pancreas and respiratory tract.
- 38What is the term given to describe the 3-8 weeks stage?Embryonic period
- 39What happens during the embryonic period?Organogenesis
- 40What happens in organogenesis?Stem cell populations establish each of the organ primordia and are sensitive to genetic and environmental influences. This is the period when most structural birth defects are induced.
- 41What are the common stages of development?1. Fertilisation
2. Cleavage to form the blastula
3. Gastrulation to reorganise the structure of the embryo and generate the germ layers
4. Neurulation
5. Organogenesis - 42What is epigenesis?A simple embryo with a few cell types in a basic pattern is gradually refined to generate a complex organism with many cell types and showing highly detailed organisation.
- 43What are the five key processes in development?q1. Growth
2. Cell division
3. Differentiation
4. Pattern formation
5. Morphogenesis - 44What is genomic equivalence?Almost all somatic cells have a complete copy of the genome
- 45What is the evidence for Genomic equivalence?Somatic Cell Nuclear Transfer. The technique consists of taking an enucleated oocyte and implanting a donor nucleus from a somatic cell. Offspring are all genetically identical to the donor nucleus.
- 46What processes are involved in differential gene expression?Cells become different from one another during cleavage which is achieved by partitioning cytoplasmic determinants e.g. transcription factors.
- 47What are inductions mediated by?Diffusable signals or cell-surface interactions
- 48What is asymmetric division?Sister cells born different
- 49What is symmetric division?Sister cells become different as a result of influences acting on them after birth.
- 50What is the role of P granules?Proteins that control orientation of the mitotic spindle segregate with P granules.
- 51What is a model organism?Suitable for experiments that address our questions about embryo development.
- 52What is the structure of a Xenopus egg?The animal hemisphere is pigmented.
The vegetal hemisphere is non-pigmented and contains the yolk which is dense. Therefore, the vegetal hemisphere is the posterior of the cell and the animal hemisphere is the anterior of the cell. - 53What is Vg1?A TGFB signalling molecule which shows mRNA to be localised at the vegetal pole.
- 54What is VegT?A T-box transcription factor which shows mRNA to be localised at the vegetal pole.
- 55What is vegetally-localised VegT required for?Development of the endoderm and mesoderm. VegT binds DNA and activates expression of transcription factors that mediate endoderm differentiation and Nodel TGFB signalling factors which induce responding cells to form the mesoderm ("induction").
- 56What is the evidence for VegT function?Expressed in the right cells at the right time
Necessary for that function to take place
Sufficient for that function to take place - 57Where is the VegT gene normally expressed?VegT mRNA and protein can be detected in the cells that will give rise to endoderm.
- 58Where is the ectoderm located?Animal hemisphere
- 59Where is the endoderm located?Vegetal hemisphere
- 60How is development affected by blocking gene function?Removing VegT from the oocyte interferes with both endoderm development and mesoderm induction. No endoderm is formed and the mesoderm is misplaced in the VegT-depleted cell. This tells us that VegT is involved in the development of an ovum.
- 61What are the consequences of ectopic gene expression?VegT expression in the ectoderm results in expression of endoderm-specific genes in animal hemisphere. Cells in the animal hemisphere normally express ectoderm genes only. VegT is sufficient for development of the endoderm.
- 62What is ectopic gene expression?A gene is expressed abnormally; where it is not usually expressed.
- 63What is the role of Wnt signalling?B-catenin accumulates in the nucleus and activate target gene expression.
- 64What is the role of GSK3 in Wnt signalling?When Wnt is absent, GSK3 phosphorylates B-catenin so gene expression is not activated in the nucleus.
When Wnt is present, a protein complex forms and inactivates GSK3 so B-catenin can enter the nucleus.
When B-catenin enters the nucleus, GSK3 is no longer able to phosphorylate B-catenin so the protein accumulates. - 65What is the role of B-catenin?Acts as a transcriptional activator - requires TCF. This causes a change in gene expression.
- 66What does sperm entry cause?The cortical reaction is triggered. Dorsal determinants that initiate Wnt signalling are translocated and the dorsoventral axis is established.
- 67What results of the cortical reaction?Wnt11 and inhibitory GSK3 binding protein is redistributed to the dorsal side where Wnt signalling pathway is activated.
- 68Where are dorsalising factors located?Vegetal hemisphere
- 69Which hemisphere does sperm always bind to?Animal hemisphere
- 70What inhibits GSK-3?Wnt11 and GSK-3 binding protein. This allows B-catenin to be stabilised in the dorsal cells. Ventral nuclei don't receive B-catenin.
- 71What is B-catenin essential for?Dorsal development.
Overexpression and depletion of B-catenin show it is required for normal development of dorsal axis structures and for head development.
Gain of function gene can produce a second dorsal axis and a second head.
Loss of function gene causes embryo to fail to produce a dorsal axis. - 72What does B-catenin activate?Expression of dorsal transcription factors such as goosecoid.
B-catenin interacts with TCF-3 to activate expression of siamois which activates expression of goosecoid. - 73What activates Nodal expression?VegT and B-catenin, which results in a Nodal gradient across the endoderm. High Nodal plus B-catenin induces dorsal mesoderm ("organiser").
Low Nodal plus VegT induces ventral mesoderm.
Nodal signalling factor is able to travel up to the animal hemisphere. - 74What is the role of the organiser?Secretes signals that pattern the mesoderm and neuralise the dorsal ectoderm. The ectoderm is too far away from the organiser so remains as the epidermis.
- 75What induces a secondary axis complete with head and nervous system?Grafting dorsal organiser cells to the ventral side of a host.
- 76What is the role of MyoD?A muscle-inducing transcription factor which causes cells to differentiate into skeletal muscle.
- 77What can overexpression of MyoD cause?Non-muscle cells convert to muscle cells
- 78What is the Cell Lineage?The developmental history of a differentiated cell, traced back to the cell from which it arises.
- 79What is the fundamental level of control of differential gene expression?Transcription
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- Beschreibung
- Undergraduate Genetics and Evolution Karteikarten am Developmental Biology, erstellt von Olivia Hearn am 09/05/2019.
- Erstellt von
- Olivia Hearn
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