Lecture 33. Multicellular Organisms 2 Flashcards
What makes up the animal pole?
Ectoderm layers
What makes up the vegetal pole?
Endoderm layers
What is already present in the egg before fertilisation?
Polarity
What do the animal and vegetal hemispheres contain?
Differing selections of mRNAs
What causes the asymmetry of mRNA?
Cortical rotation triggered by fertilisation that offsets the animal pole
What occurs 1 hour after cortical rotation?
Cleavage
What does cleavage result in?
Many small cells (blastomeres) without significant change in mass. Molecular components become differentially distributed in cells. First differences in cell fate
Ectoderm
Predominantly Animal blastomeres
Mesoderm
Middle cells
Endoderm
Vegetal blastomeres
What happens to the embryo after cleavage?
It becomes a hollow ball of cells called a blastula
How many germ layers are blastomeres predetermined to become?
3
What is gastrulation?
The process of the tissue germ layers and body axis being laid down via specific choreography of cells
What happens to cells during gastrulation?
Cells are spatially rearranged with some undergoing involution
What molecules play a major role in neurulation and somite formation?
Cadherins and other cell-cell adhesion molecules
What is neurulation?
When ectoderm roles into a tube which becomes the neural tube between the brain and the spinal cord
Limb bud
Embryonic connective tissue with Sonic Hedgehog protein expression
What is epigenetics?
The processes which govern the evolution of an individual’s phenotype from the genome
What 3 mechanisms result in chemical modifications in chromatin structure?
Methylation of the DNA
Acetylation of histones
miRNAs also play a role
Embryonic development in plants
Begins at fertilisation
Division of the zygote - asymmetry - polarity of the embryo
Diploid embryo - polarised ball of cells
Two groups: one at suspensor end (root) and one at opposite end (shoot)
What allows sequential growth in the plant?
Apical meristems (groups of self renewing stem cells)
What regulates plant growth?
Hormones
What are the 3 phases of plant morphogenesis leading to modular construction and flower formation?
Cell division, Cell growth and Cell differentiation
