PART 1 Flashcards
What are the two opposing theories of plant development?
- Preformationism= Nicolas Hartsoeker (1695)- organisms develop from miniature preformed versions of themselves, hommoculus
- Epigenesis= Aristotle- new structures slowly added to form whole body
The cell Theory- Robert crooke (1665)
- All organisms are composed of 1 or more cells
- Cell most basic unit structure
- All cells arise from pre-existing cells
What is germ plasm determinants theory?
Fredrick Weisman 1880s
Germ cells have whole collection of somatic cells which have subset of determinants.
Carry out specific characteristics determined
Wilhem Roux- 1888
Killed one half of frog egg with hot needle.
Half remains dead the other half embryo
Induction theory
Separated embryo at stage 2 and 4
both reform themselves and fully develop
NOT in contact with each other, disrupt communication and modify same outcome
How do cells aquire new properties that differentiate them from others?
Cell division- symmetric or asymmetric
Cell-cell communication
Cell adhesion- condensation or dispersal
Cell shape-epithelial or epithelial to mesenchymal
cell migration
cell death
What are the different types of cell-cell communication
Paracrine= Signal produced in one cell and binds to another
Autocrine= provides on one cell, acts on other side of same cell
WNT, SHh, TGF, BMP signalling ^both above
Juxtacrine= cell/cell contact
Cell signalling- cell-cell interaction
Cell needs to be competent- receptor for signal and machinery
signal can be instructive (initiates new programme, direct change in cell) or permissive (changing environment for another to react)
signal can act as morphogen
What does transmission of signal to the nucleus involve
Signal transduction cascade
What are the 3 germ layers?
- Ectoderm (external layer)= Skin, brain/neurons and pigment cells
- Mesoderm (middle)- Cardiac, skeletal, RBC, smooth muscle
- Endoderm( Internal layer)= Lung alveoli, thyroid and pancreatic cell
What 2 methods is tissue homeostasis maintained by?
- Negative feedback loop
2. Stem cell mediated repair
What is pattern formation in embryonic development?
Process where cells are ordered within embryo.
Need Co-ordinates to establish axis
What is morphogenesis?
Cell and tissue movement and behaviour changes in cell
Factors affecting morphogenesis of cell?
Cell adhesion
cell death
cell migration
cell shape
Step by step series of differentiation of cell in embryonic development
- egg/sperm
- Specification- early commitment, not stable
- determination- commitment to cell fate, stable , still aquisation of terminal characteristics
- Differentiation- reversible
- Maturation- irreversible
What are the processing underlying embryonic development?
Growth
Morphogenesis
cell differentiation
pattern formation
Growth of embryonic development
- continuous process
- growth rate varies depending on age
- cell proliferation, enlargement and accretion
What are the two opposing theories in early embryonic development in vertebrates?
- Funnel (Haeckal)= Few differentiate in early development X wrong
- Hourglass (van baer)= Lots of differentiation beginning and end Correct
Methods to find out where and when a gene is expressed in the embryo
- In situ Hybridisation
- Northern blott
- RT-PCR
- Microscopy
- reporter lines (transgenic)
What is a method to find out how many transcript is in an embryo?
Northern blott
RT-PCR- carry out amplifcation of gene expression
Is the protein expressed with the same timing of the gene?
Look at mRNA and protein as the protein may not be expressed where it is transcribed
look at distribution of protein- western blot (how much protein made) or immunochemistry (temporal and spatial
To find out if the gene/ protein is essential for development
Loss of function- disrupts expression
gain of function- increase amount of activity to gene product encoded by mutant gene
Forward and reverse genetics
Forward Genetics
C.elegans, drosophilla, mouse and zebrafish
Seeks to identify gene whose mutant causes a specific phenotype.
Cross mutant and WT- F3 generation gives m/m (mutant), m/+, +/+
Reverse Genetics
Target 1 gene you are interested knowing function of by two main methods:
- Straight KO
- Conditional KO
- homologous recombination(loxp)
- Es cells transfection
- ES cell selection
- Es cell injection into blastocyst
- Implant into mouse
- Selection of chimeric mouse
- breed either conventional KO or conditional KO (floxed allele with tissue specific cre mouse)