Lecture 2 - Animal Devlopment Flashcards
(35 cards)
Morphogenesis
Occurs via changes in cell position, shape, survival, and form of organs
- rearrangement of cells or sheets
Fertilization
Haploid gametes join to form a diploid zygote
Model Organisms
Easy to study but broadly representative
- Development al genes and mechanisms are similar across animal species
-Studying development in model organisms provides knowledge about development in general
Gametes in sea urchins
Sperm and egg are the haploid gametes
-Egg cytoplasm contains many proteins and mRNA involved in early development
Fertilization in sea urchins - step 1
Sperm contact with the jelly coat triggers the acrosomal reactions
- This is what allows the sperm to reach the egg - the kind of softening of the egg
Differential Gene Expression
Foundation of diverse cell types and behaviors through development
Fertilization in sea urchins - step 2
Surface proteins on acrosomal process bind to receptors on egg cell membrane
Fertilization in sea urchins - step 3
Plasma membrane fuse, triggering fast block to polyspermy
- polyspermy - the oocyte is penetrated by more than one sperm
-fast block is a reversal of polarization to repel the other sperm
Fertilization in sea urchins - step 4
The sperm nucleus enters and the cortical reaction causes a slow block to polyspermy
-Perivitelline space occurs - a physical separation from the outside and inside of the egg, this is the slow block
Fertilization in sea urchins - step 5
Fusion of sperm and egg nuclei form the diploid nucleus of the zygote - there is a small clear envelope around the zygote called the fertilization envelope
Cleavage
-the process by which the zygote becomes multicellular
-Rapid cell division with little growth of individual cells
(G1 and G2 phases
skipped)
-results in blastomeres
Blastomeres
smaller cells resulting from cleavage
What does cleavage result in?
-Cells getting smaller and smaller with each round of division
- No growth of cells between divisions
In frogs
Zygote becomes a blastula
Blastula
A hollow ball of cells with a fluid-filled cavity called the blastocoel
-There is an animal pole and a vegetal pole
- where sperm hits the egg becomes the animal pole (smaller cells, less ‘yolky’)
Differential gene expression
- cells express different genes depending on their location and the stage of development
- expressing different genes leads to the production of different proteins (this, in turn, determines the structure and behaviors of the cell at any given time)
Cytoplasmic determinants
A signal given within the cell determines how the gene is expressed
-molecules within the cytoplasm regulate gene expression
- can be differently distributed to daughter cells resulting in differences in gene expression
Inductive signals
A signal from outside of the cell determines how the gene is expressed
-The signal molecules that a cell is exposed to depends on its location within the embryo, and the stage of development
Embryotic stages - Cleavage
converts the unicellular zygote into a multicellular embryo
Embryotic stages - Blastula
a hollow ball of cells
Embryotic stages - Gastrulation
where the three germ layers are formed
Gastrulation
Stages when the three germ layers are established and the basic body plan is set up
-Results in a three-layered gastrula
Organogenesis
formation of the organs
neurlation
formation of the nervous system
- is an example of organogenesis
