Development Flashcards
What two cell types have formed at the blastocyst stage?
Give an example of what they become
Trophectoderm - extra embryonic tissue e.g. placenta
Inner cell mass - epiblast which becomes embryo proper and hyperblast
What two classes of proteins are abundant in eukaryotes?
Transmembrane molecules for signalling and adhesion
Gene regulatory proteins
What is the overall purpose of gastrulation?
How does this happen?
Purpose - form 3 embryonic germ layers: endoderm, ectoderm, mesoderm
How - first cells invaginate = endoderm
Last cells = become mesoderm
Cells in between = ectoderm
What does it mean for a cell to be determined?
A cell is fated to become a specific cell type e.g. the transplantation of a germ cell from one layer to another will still be determined to a cell type of the original location
What does it mean for a cell to have positional value?
When a cell is determined to a region but not to a particular part e.g. grafting a cell that is usually thigh to a wing forms a toe
Fill in the blanks:
Gene expression regulates __________ _________ as artificial expression can grow leg like characteristics in a wing e.g. ___ or ____ can give this phenotype and are responsible for _____ release
Positional value
Tbx
Pitx1
Fibroblast growth factor 10 (FGF 10)
What are the effects on a mouse lacking FGF10?
What does the implantation of a bead soaked in FGF10 cause?
Develop without limbs
Implantation can cause a limb to grow where it usually wouldn’t
What’s a the difference between symmetric and asymmetric cell division?
Symmetric cell division is the result of a cell dividing into two symmetric daughter cells that become different after birth due to influences
Asymmetric however, are born different due to collection of molecules at different points in the cell
How does positive feedback create diversification?
In a homologous system, lateral inhibition can produce a positive feedback loop that amplifies changes between the two cells to create asymmetry
What does notch signalling control?
Lateral inhibition, i.e. a signal that acts on neighbouring cells and stops them from developing into the same type as the releasing cell e.g. nerve cells in Drosophila cause lateral inhibition, causing others cells to become epidermal instead. This caused by a signalling protein, Delta, activating the Notch receptor
Match the ligand with its receptor:
Hedgehog Notch
Wnt Frizzled
Delta Patched/Smoothed
Hedgehog Patched/Smoothed
Wnt Frizzled
Delta Notch
What do morphogens do and how do they create their varied response? Give an example
They are signalling molecules that exert different developmental effects based on their concentration e.g. sonic hedgehog signalling
How do nurse cells aid in embryo development?
They release mRNAs and proteins that code for essential oocyte maturation and function in early embryo development
What are the four types of early development genes?
What effect do mutations have in these genes?
Egg-polarity genes
Gap genes - elimination of one or more groups of adjacent segments
Pair-rule genes - delete alternate segments
Segment polarity genes - deletion of alternating segments and replacement with a mirror image duplicate
Name the four egg polarity genes and the section they regulate
Nanos - posterior
Bicoid - anterior
Torso - terminal (RTK)
Toll - dorsoventral (transmembrane protein)
Nanos and bicoid both regulate which protein? How do they do it?
Nanos represses hunchback by binding to its 3’ UTR region (mRNA) in the posterior end
Bicoid produces a protein that expresses hunchback as the gene has three low and three high affinity binding sites
What are gap genes? Give some examples
Gap genes control body segmentation
Krupple, knirps, giant and tailless
