Development Module Overview Flashcards
What is developmental biology?
The study of how a fertilised egg becomes an adult organism, how we reproduce
What is the purpose of developmental biology?
Lets us understand birth defects
Leads to better treatment of disease
What are model organisms?
Species that are used for study
What is a Parhyale hawaiensis and why is it a good model organism?
Has short generation time
Has high regenerative capacity
Is transparent which is good for imaging
Undergoes transgenesis
Why are model organisms useful in developmental biology?
We can identify conserved mechanisms for development
We can understand how diversity was achieved in the history of life
We can understand the cause of congenital disease
We can investigate repair and regeneration to help treatment
What is descriptive embryology?
Developmental stages based on visual stages of development
In and out of embryo
What is experimental embryology?
Experiments that aim to define how embryonic development occurs
What is morphogenesis?
The process where form is generated
What is gastrulation?
A morphogenesis process where the endoderm, mesoderm and ectoderm layers reach their final positions in the embryoW
What is neurulation?
A morphogenetic process where the nervous system begins to form
What is a blastomere?
A cell in the early embryo
What is a fate map?
The assessment of the fate of a cell based on its lineage, ie whats going to happen to the cell
What is a specification map?
The assessment of what a cell will form if they’re taken out of the embryonic environment
What is the meaning of determined in developmental biology?
When a cell or tissue is determined, it will develop according to its fate even when its in another site in the embryo
What is the difference between a fate map and a specification map?
If the fate map matches the specification map then the cells don’t rely on cell-cell communication to achieve their normal fate
If it doesn’t match, the cells receive signals at a later point in development before assuming their normal fate
What is the meaning of competence in developmental biology?
The range of cell fates that can be achieved by a cell
The possibilities a cell is able to become
What is induction in developmental biology?
The process where cells give off signals to neighbouring cells which changes their fate
What is the organizer experiment?
There was the induction of muscle and neural tissue
They found the dorsal mesoderm is determined by the early gastrula stage
The ventral ectoderm and mesoderm are competent to become neural and somitic tissue
What is homeotic mutation?
A mutation that results in the transformation of one body structure into another
What is a hox gene?
A family of genes that encode related transcription factors, characterised by having a DNA binding domain called the homeobox
They are evolutionarily conserved
They are found clustered in the genome
Where were hox genes first identified?
In Drosophila
They were involves in anterior posterior patterning
What are the different ways that genes can duplicate?
Tandem gene duplication
Segmental duplication
Whole gene duplication events
What is tandem gene duplication?
Occurs when there is a chromosome mis pairing in meiosis, which causes unequal crossover
Can cause paralogous genes, where there are duplicates genes in the same genome
Or orthologous genes, where there is the same gene in different organisms
Can cause subfunctionalisation
What is segmental duplication?
Similar to tandem gene duplication but happens on a larger scale
A whole chunk of a chromosome is affected
What are whole genome duplication events?
Events that affect the entire genome
Can be allotetraploidy or autotetraploidy
What is allotetraploidy?
A whole genome duplication event
When there is hybridisation between two different speciesw
What is autotetraploidy?
A whole genome duplication event
When there is duplication of the genome due to improper meiosis
What occurs in two rounds of whole genome duplication? (What is the 2R hypothesis)
There are 5 stages that occur during 2 rounds of whole genome duplication events
1. The ancestral cluster is present
2. Duplication event happens, the cluster is duplicated
3. Gene loss events, some genes in each cluster are lost
4. Second duplication event, each cluster is duplicated without duplicating the missing genes
5. More gene loss happens at random
What is the result of two rounds of whole genome duplication?
Results in 4 hox clusters in vertebrate lineage
Results in 39 hox genes
Evolved from a set of 13 paralogous groups on each chromosome
What are the three types of evidence showing that hox gene expression gives positional identity along the anterior-posterios axis?
- expression pattern
- comparative embryology
- gene knockout experiments
What is comparative anatomy as evidence for hox gene expression and positional identity?
We can compare the anatomy of different animals and their hox genes to see if their is a correlation between their different hox genes and different anatomy
What is the gene toolkit?
The ancestral function for hox genes are for anterior posterior patterning
They can be coopted for new functions
Hox genes are expressed in distinct proximal distal patterns
What is the relation between hox genes and proximal distal identities?
They control proximal distal identities and patterns
What are homologous genes?
Genes that share a common ancestral gene
What is gene redundancy?
When there is no phenotype observed when a gene is mutated because another gene fills inf or the function of the mutated gene
This filler gene is usually a paralogous gene and means that a paralogous gene can mask a mutated gene
What is the meaning of potency?
The range of cell fates available to a cell
What does totipotent mean?
When a cell can become all cells of the embryo
What does pluripotent mean?
When a cell can become most but not all cells of the emrbyo
What does bipotent mean?
When a cell can become one or two cell types
What does unipotent mean?
When a cell can only become one cell type
What is the waddington landscape?
A model showing how potency decreases over time
Once the ball goes down one of the paths of potency, it cannot change to another path
What is the argument against the waddington landscape?
That using nuclear reprogramming, it is not a one way road to differentiation
Using nuclear reprogramming, we can reprogramme cells back to embryonic pluripotent state
How can pluripotent cells be made?
The epiblast cells of pre-implantation blastocyte embryos can be isolated and grown in culture
They are pluripotent
What is a hES cell?
Human embryonic stem cell
What is an iPS cell?
An induced pluripotency stem cell
What is the process of nuclear reprogramming?
Reprogramming differentiated cells back into a pluripotent embryonic state without using nuclear transplantation
Uses iPS cells
The cell culture is taken and pluripotency genes in a vector are added
The cells are added to feeder cells and are cultured in an ES medium
Colonies appear and this makes pluripotent stem cells
What are stem cells?
Cells with the indefinite capacity to self renew
They can differentiate into at least one cell type
What is a progenitor cell?
Cannot renew indefinitely
Can differentiate into at least one cell types
What is the role of adult stem cells?
To replace cells throughout life, for example blood stem cells and stem cells in skin and hair follicles
They are sensitive to radiation and chemotherapy
What was the first successful example of stem cell therapy in humans?
Bone marrow transplantations
They effectively transplant hematopoietic stem cells into patients
