Dr Boswell's lectures 1 Flashcards
What are the two possibilities for animal development?
Preformation theory
Epigenesis
Who came up with the cell theory?
Schleiden and Schwann
Who came up with the germ line concept?
Weismann
What processes are needed for cell development?
Cell division Pattern formation Morphogenesis Differentiation Growth
What are 5 key cell activities?
cell-cell communication cell shape movement cell movement proliferation death
What is the A/P axis
Anterior/posterior (head/tail)
What is the D/V axis?
Dorsal/ventral (back/front)
What is the P/D axis?
Proximal/distal (near/far)
What is pattern formation?
Cells become organised in time/space and acquire an identity about what they will become
What does the endoderm become?
gut, liver, lungs
What does the mesoderm become?
skeleton, muscle, kidney, heart, blood
What does the ectoderm become?
skin, nervous system
What determines mosaic development? Is it influenced by the environment?
depends on specific determinants in develoment that are distributed unequally to daughter cells, environment cannot influence it
What determines regulative development?
depends on interactions between between ‘parts’ of the developing embryo by cell-cel communication, can be influenced by environment
Who did experiments on mosaic development and what with?
Roux, destroyed one cell of a two-cell frog embryo
what kind of development do sea urchin’s show?
Regulative
What is cleavage?
rapid cell division after fertilisation without growth
What are the two egg axes?
yolky - ANIMAL pole
non-yolky - vegetal pole
Who observed yellow cytoplasm in the tunicate egg?
Conklin
What are the key patterns of cleavage?
Spiral (Protostomes)
Radial (Deuterostomes)
Superficial
What is gastrulation?
formation of the main gut and body plan
In larvae, what do animal half embryos normally form?
larvae with no gut
What can micromeres do to the cells above them?
change their fate
What do lithium ions do to larvae?
vegetalised larvae
Whats do zinc ions do to larvae?
animalised larvae
Who developed the french flag model?
Lewis Wolpert
What is Beta-catenin and what does it do?
a TF derived from maternal RNA
specifies micromeres
What environmental signals can change cell fate?
morphogens such as beta-catenin
What are GRNs
Gene Regulatory Network components - they are regulatory genes
What are kernals?
GRNs for a given developmental function
What is oogenesis?
egg formation
what is spermatogenesis?
sperm formation
what are some features of an oocyte?
storage molecules ‘yolk’ containing vitellin
mitochondria, ribosomes, storage RNA
What are the categories of oogenesis?
Solitary
Follicular
Nutrimentary
What are the two synthetic pathways for the stored yolk in the cytoplasm?
Autosynthetic oogenesis
Heterosynthetic oogenesis
What are the properties of oocytes in follicular oogenesis?
oocyte associated with a covering of somatic cells
Where is follicular oogenesis found?
Ascidiella aspersa - a tunicate
What type of ovaries do locusts have?
panoistic
In the drosophila fruit fly, what is the type of oogenesis?
nutrimentary oogenesis
What is autosynthesis, where can it b observed and how
the synthesis of yolk and other stored materials by the oocyte itself, can be labelled with radioactive tritium and is often seen in polychaetes
What is heterosynthesis, what is the evidence for it?
synthesis of yolk proteins by other, non-germ cells, characterised by uptake of vitellin
evidence from electron microscopy
What did Nusslein-volhard and Weischaus do?
treated flies with chemical mutagen
classified thousands of drosophila mutants
determined maternal effect genes
Maternal effect genes did what to drosophila body segments?
some segments did not develop
what does bicoid mRNA do?
forms a concentration gradient in Bicoid protein
Which part of the drosophila larvae does the bicoid mRNA affect?
It specifies the anterior part of the anterior-posterior axis
Where is the nanos mRNA found?
the posterior
what does nanos suppress translation of?
maternal hunchback mRNA in posterior
what does Bicoid promote?
production of embryo’s hunchback protein in anterior
How do maternal RNAs become distributed?**
gurken mRNA (mother) translated in posterior
binds to Torpedo receptor in cells
posterior follicle cells rearrange microtubule in cytoskeleton
maternal mRNA in nurse cells transported to locations
posterior localisation of maternal oskar RNA needed for nanos mRNA in posterior
What are gap genes?
First zygotic genes to be expressed along AP axis, code for transcription factors, often cause deletions
hunchback is a gap gene
What do gap genes do?
interact to define boundaries of expression of other genes
What are pair-rule and segmentation genes?
define segmentation, pair rule genes are expressed in alternate segments
name two pair rule genes
even-skipped and fushi tarazu
how can you see eve and ftz?
antibody staining
What are segment polarity genes? name one and say what it does and where it is found
Engrailed, helps define parasegment boundaries, found in anterior region of parasegment
What is an imaginal disc?
pad of undifferentiated cells in larva, each disc has its own fate map
what is transdetermination?
imaginal disc producing a part it should does not usually produce
What is homeosis?
transformation of one body part onto another
what are homeotic mutants?
homeotic genes that alter appearance of a segment
How were Hox genes discovered?
homeotic mutations mapped by Ed Lewis
What are the two Hox gene clusters?
Antennapedia
Bithorax
What is the homeobox
a region of DNA in homeotic genes that codes for the homeodomain
What is a homeotic gene/homeotic selector gene
a gene which defines a region or position of the embryo (eg. a segment)
What is a Hox gene
a family of homeobox-containing genes that are part of a homeotic gene complex
What forms P/D axis of drosophila?
Distal-less (DII)
What is DII inhibited by?
Abd-a/Ubx in abdomen
What is neurulation
inwardly migrating cells form roof of archenteron, these cells form dorsal mesoderm
Cells that overlie mesoderm cells form what?
neurectoderm
How do these cells form a neural tube?
neural plate > neural groove > neural tube
What did Spemann term the process of the underlying mesoderm and its role?
primary embryonic induction
What happens if the grey crescent is not present?
no dorsal structures develop
Define ‘determination’
a stable change in the internal state of a cell such that its fate is then fixed
define ‘induction’
one group of cells signals to another group of cells in the embryo and so influences how they will develop
define ‘primary embryonic induction’
the induction of a whole body axis
How does the Spemann organiser form?
Beta-catenin gradient, synthesised throughout embryo
Dishevelled in vegetal pole
After fertilisation, dishevelled transported by microtubules along corticol cytoplasm to future dorsal region
GSK-3 blocked by Dsh in grey crescent
What does BMP4 do?
inhibits cells from forming neural tissues, promotes formation of ventral structures
What 3 axes does the pentadactyl vertebrate limb have?
P/D
A/P
D/V
What forms limb buds?
mesenchyme cells that form under ectoderm
What happens if AER is removed?
limb ceases to grow outward
Where do Hox proteins act?
in body segments to determine limb bud identity
where is the signalling centre located and what is it called?
posterior region of limb bud, zone of polarizing activity
What is signal for apoptosis provided by?
Bone morphogenetic proteins (BMP)
What is syndactyly?
webbed-fingers
