Final time Baby (should we kill ourselves!?!!) Flashcards
inner membrane of the egg which is used to protect the developing fetus
Amnion
Function of A, B, and C genes in flower development
- A function- Whorl 1, sepals
- A+B function-Whorl 2 petals
- B+C function- Whorl 3 Stamen
- C function- Whorl 4 Carpel
Steps in neurlation in a chick
1)notochord forms
2)somites form
3) neural folds form and close to form the neural tube
4)gut forms
5) the anterior end is ahead in development
Neural Crest Cells
Cells formed adjacent to the neural plate which will migrate and differentiate into many different cell types at target locations. Required for formation of the head
Gastrulation in the zebrafish
1)Epiboly- animal pole cells spread over and around the vegetal axis, involves intercalcating of various cell layers
2)Involution- folding of the blastoderm inward of the embryo to form the gut
3)Convergence and extension- the cell layer elongates and converges along the dorsal layer to produce the fish shape
Draw the interaction between MACHO and FGF in ascidians to determine cell fate
Dickkopf
WNT inhibitor needed for head development
VegT (mesodermal development)
Signals for endodermal development and induces Nodal
encodes a signal of the TGF-β family playing a role in mesoderm induction
Vg-1
Protein that is transcribed in plants to produce FT protein which trigger flowers. In short cycles its peak production is at night where it is degraded and in long cycles it is able to accumulate in the budding flower
CO
Spemann organizer transplant experiment results
Transplant of Spemann organizer (early)- duplication of the embryo forming mesoderm and ectoderm
Transplant of the Spemann Organizer (late)- induction of posterior structures only
Meaning: Spemann organizer changes position and function through development
Consists of ectoderm and a mesenchymal core forming the skeletal structures
Limb bud
Ectodermin
(mesoderm development) Produced in the ectoderm and inhibits nodal
Signal produced by endoderm that leads to mesenchyme and notochord specification (asicdians)
FGF
Explain sex determination in C.elegans
- C.elegans use XX=hemaphrodite and XO=male
- Uses cell to cell interactions and a counting mechanism to turn on or off the Xol-1 gene
Vagal and sacral neural crest
parasympathetic ganglia of the gut
What happens when A, B, and C genes are lost in a flower?
Loss of A- Loss of sepals and petals, duplication of stamen and carpels
Loss of B -Loss of petals and stamen, duplication of sepals and carpel
Loss of C- Loss of stamen and carpel, duplication of petals and sepals
cavity formed during involution which will become the gut
archteron
Two signal model
Two opposing signals (FGF and retinoic acid) specify initial fates. Later cells in the middle, which are outside the range of both signals, form intermediate structures
How Limb position is determined
Hox genes Confine of specific transcription factors along the A-P body axis
Steps in drosophilla eye formation
- Ato is uniformly expressed in the photo-receptor precursors by a hh signal
- Lateral inhibition through Delta/Notch signalling ensures that only one cell in each group expresses Ato and becomes specified as R8 cell
- Signals from R8 induce neighbouring cells to become R2 and R5
- they signal to neighbouring cells to become R3 and R4.
- R1 and R6 are induced on the other side and in combination with R8 induce R7
- Cone cells are then specified
later developed axons that use the pioneer axons tracks to navigate the neuronal circuit
Follower axons
Signals required to develop endoderm and mesoderm
VegT- Develops endoderm
Nodal-Triggered by VegT and develops mesoderm by inhibiting Fox1 E
Ectodermin- Spawns in the ectoderm and degrades nodal pathway
acts as an attractive force for dorsal interneurons and is the homolgue to UNC-6 in vertebrates and forms a gradient out of the floor plate
Netrin-1
Germ cell differentiation in mammal eggs vs sperm
- Mammals egg have primary oocytes that arrest development until sexual maturity and are stuck in metaphase 2
- Mammal sperm- Primordial germ cells in males arrest in the G1 phase of a mitotic cell cycle in the embryo.Act like stem cells after signalling from cells in the testis
Human implantation of embryo
- Trophoblast cells dig into uterine epithelium and froms a connection known as the body stalk
- blood vessels grow into the body stalk
- maternal blood vessels bath the fetal ones in blood
Cranial neural crest
form cartilage, bone, cranial neurons, glia and connective
tissue of the face; also bones of middle ear and jaws
Signals important in regionalization of the brain
Otx and GBX2- divide the brain into hind and forebrain and work as antagonists for one another.
ANR and MHB produce signals which pattern the regions adjacent to them
Notochord and floor plate determine D-V axis formation
a substance that can cause birth defects
Teratogen
Explain sex determination in Drosophilla
- Drosophilla use an XY system but the mechanism behind sex is a binary switch turned on and off by the count of autosomal to X chromosome ratio
- X chromosome makes an activator for the switch and the autsomal chromosomes make a repressor
- Due to the ratio of X to autosomal genes in females the Sxl gene is on where as in males it is off
Nieuwkoop center formation and signal
- Forms when the wnt signal is completed and maternal VegT is present
- Signals for Spemann organizer and for duplication of the axis
movement of ectodermal cells to the outer surface of the blastula
Epiboly
Scleretome signal for development
Signal for development is Shh which induces Pax-1 expression which triggers Scleretome development. Induced the floor plate of the neural tube and the notochord
Explain a technique which can prevent polyspermie
- Coritcal granules fuse with the membrane and this in combination with the vitelline membrane prevent additional sperm entry
- Sea urchins use membrane depolarization
code for the different vertebrate identities
hox genes
How is leg axis formed?
Again uses en and hh but Dpp is only on the dorsal side and wingless on the ventral side
- Distalless is expressed in the center between Hh, Wg, and dpp
- Wh/hh will work to activate DII and Hth
- DII and Hth activate Dac working together to create the proximal-distal axis
movement of cells around the inner surface of the blastula
Involution
Reelin
Reeling gene codes for a protein that binds to ApoER2 and VLDLR which are receptors found on migrating neurons. It is either a stop signal for migration or an attactive cue to bring neurons to the correct locations
cell layer above the yolk in chickens that will form extra embryonic tissue providing access to the yolk.
Hypoblast
Explain a tactic for attracting sperm to egg
sea urchins- release peptides which attract sperm form the same species
Three different neuron types and their location of origin
Commisial neurons- Dorsal portion of neural tube
Motor neurons/interneurons- form from ventral portion of neural tube
Sensory neurons- neural crest cells
gene required for development of eyes, directly regulates opsin expression in
photoreceptors
Pax-6/eyeless
loop located within the primitive streak, regression of this node towards the posterior signify the end of gastrulation and begging of neuraltion and somite formation
Hensons node
Nodal
Triggered by VegT and triggers development of mesoderm as well as inhibition of Fox1 E
Pioneer Axons
Fist axons sent out in the growth pattern, using guidance clues for the environment the figure out the path for all remaining axons to take
Explain sex determination in mamals
In mammals we use the XY system where the presence of the Y chromosome has a transcription factor SRY which leads to the male phenotype
How to create a cDNA library
1)isolate mRNA from source material
2) reverse transcribe into cDNA
3)clone into expression vectors
4)transform bacteria with vectors (note: each cell
will have one plasmid with one cDNA
top layer of cells above the yolk that will develop into the embryo
Epiblast
Epiboly
Endoderm and mesoderm invaginates, epidermal cells extend to cover the entire embryo
A-P axis of retinal neuronal growth
EphA and ephrins form gradients (A-P) in the retina and tectum respectively. ephrin and EphA together cause growth cone collapse
High EphA neurons stop growing in areas of low ephrins
Low EphA neurons collapse at higher levels of ephrins
Robo Mutant
frequent crossing of neuron tracks , Robo is the receptor for Slit.
signals for ventral mesoderm (blood, kidney)
BMP
Portion of the paraxial mesoderm that forms the dermomyotome
all segmenets that are not the ventral lateral form dermomyotome- splitting later into the dermotome and myotome, giving rise to dermis and trunk muscles respectively.
How does the growth cone move?
Filopodia are dynamic structures with an actin core. Positive guidance signals lead to stabilization of filopodia, negative signals lead to collapse.
form in contact with ventral neural tube or notochord
Cartilage
Slit Mutant
collapse of axon track- everything gets spaced close together, Slit is a repulsive guidance
Explain how mesoderm leads to development of neural plate axis
Mesoderm produces a gradient of WNT signalling molecules that lead to A-P diffrentiation. With high WNT concentrations leading to posterior structures and low WNT concentrations leading to anterior ones
Inhibition of WNT and BMP is required for head development! Ex. dickkopf
How is the A-P axis determined for drosophilla wings
- Wings parasegment boarders are coded for by the feedback loop between Wg, Hh, and En
- Posterior portion of the wing creates engrailed with hh which activates dpp expression
- Dpp then acts like a morphogen activating Splat and Omb which in combination with dpp and engrailed leads to 6 different wing compartments
Pole plasm
Cytoplasm containing organization proteins,germ cell differentiation proteins,and somatic differentiation blocking proteins all which are necessary for development of pole cells
portion of the brain responsible for motor coordination, motor learning, balance and posture control, timing and rhythm of movements, ‘error correction’ of movement
Cerebellum
Development of chick body along A-P axis due to movement of Hensons node
Portion of the paraxial mesoderm that forms the scleretome
The vental-medial quadrant of each somite forms the sclerotome eventually giving rise to vertebrae and ribs. triggered by proximity with the notochord.
Describe the three methods for dosage compensation in animals
- Mammals- inactivate on of the X chromosomes
- Drosophilla- increase transcription of single X chromosome
- C.Elegans- Decrease transcription of double X chromosomes
Fox1 E
Inhibited by Nodal so that mesdoderm may develop
Cytoplasm from the vegetal pole of the ascidians that acts as a cell fate determinant for muscle cells
yellow crescent’ cytoplasm
form the muscles and dermis
dermomyotome
Draw the phenotype for a regular,slit,robo, and comm mutant
Neurlation in Mouse
- Anterior of the node begins to grow and notochord forms
- Neural folds appear and neurlation formerly begins
- somite formation and organogensis begins
Label the different developmental zones of the Xenopus
a)epidermis
b)nervous system
c)blood and kidney
d)Somites/ heart
e)Notochod
f)Endoderm
Mouse gastrulation
- Epiblast cells begin to move towards the primitive streak
- Primitive streak spreads out anteriorly and laterally to form the mesoderm between the visceral endoderm and ectoderm
- visceral ectoderm is replaced by definitive ectoderm
- Primitive streak continues until it reaches the bottom of the cup shape and forms a node (analogous to hensons node in chicks) which will later develop into the notochord
Cortical rotation and its effects
- Sperm enters the embryo and animal half with yolk will rotate 30 degrees with respect to the centre and aligns opposite the sperm entry site
- Inhibition of the rotation leads to a lack of dorsal structures, double rotation of the dorsalizing factors leads to conjoined creatures. LiCl leads to a double dorsalization
After Doralizing factors have completed the rotation Wnt pathway is activated and dorsal structures can form
Hox genes and limb formation
- Hox 9/10- Pattern the humerus
- Hox 10/11-Ulna/radius
- Hox 12-wrist
- Hox 13-hand
Germ cell formation in C.elegans, Drosophilla, and Mice
- In C.Elegans the C4 cell containing PIE-1 protein is what differentiates into the germ line
- Drosophilla and Xenopus germ line comes from pole cells which form at the posterior end of the embryo and develop when in contact with the pole plasm
- Mouse germ cells form in the epiblast post fertilization based on a signal from the extra-embryonic ectoderm
c-hairy I
one of the genes used in somite boundary formation and A-P somite axis formation
Label the different signals needed to form the endoderm and mesoderm
A) FOX1 E
B)Ectodermin
C) Nodals
D) VegT
Describe Drosophilla Neuroblast division
- Asymmetrical division of neuroblast forms the smaller ganglion mother cell and the larger neuroblast.
- This pattern continues as each time the neuroblast divides another ganglion mother cell is produced. As it divides different transcription factors are active (Hb, Kr, Pdm, Cas) leading to differing cell fates
Hollow ball of cells stage in the embryo
Blastula
extracellular protein that can act as a repulsive or attractive agent for neuronal growth
Unc-6
Dorsal ventral patterning of the neural tube
Shh- created on the floor part of neural tube and BMPs created from roof plate
Shh is what specifies neuronal identity through use of a moprhogenic gradient it controls the expression of class 1 and class 2 transcriptional factors
mRNA found in ascidians that causes the expression of muscle cells.
macho-I
Steps involved in biochemical purification
1)fractionate source material
2) test fractions
3) repeat until substance is purified
4)determine identity (protein or organic molecule)
This is the same in modern times but utalizes cDNA libraries
Hensons node
special portion of the primitive streak in chickens that is involved in somite formation via its movement along the A-P axis
Family of ligands then when bound to the receptor triggers dimerization and phosphorylation of Smads which activate differing target genes
TGF-B
Cardiac neural crest
artery walls, part of the septum; also neurons, cartilage
Trunk neural crest
sensory neurons of dorsal root ganglia, sympathetic
ganglia, adrenal medulla; also melanocytes
Functions of the Spemann organizer
1)produces chordin and noggin to allow neural tissue development
2)initiates gastrulation
3)turns into the notochord
Cleavage of the chick embryo
- Cleavage begins but is incomplete, this leaves a gap
- Gap (subgerminal space) expands
- Cells move around this cavity (not gastrulation) over the yolk layer
- Top layer will form the embryo (epiblast) and bottom layer will form the connection point for nutrient uptake from the egg(hypoblast)
Implantation of embryo for mouse
- Trophoblast cells attach to the uterine lining
- Epiblast (top half) elongates and develops into a cup shape
- Afterwards the primitive streak will form at the posterior end marking the beginning of gastrulation
How is Mesoderm specified?
- Mesoderm is formed when there are interactions between vegetal and animal caps
- Vegetal cells cause animal cells to form mesoderm
- Dorsal vegetal cells lead to muscle and notochord
- Ventral vegetal cells lead to blood
Explain how sperm is able to enter the egg
zona pellucida proteins are recognized by the sperm and trigger the ‘acrosomal reaction’ leading to release of enzymes which help to break down zona pellucida components
each of the optical units that make up a compound eye, as of an insect
ommatidium
Neurlation in the Xenopus
- Neural grooves form above the Notochord, the side walls pinch upwards and form a peak along the neural groove
- Neural folds are elevated and apical constriction occurs
- Hinge points fold inwards and the neural crest forms a closed loop at the top with the neural tube in the centre
Outer membrane of the egg which is used to perform gas diffusions
Chorion
determines position of growing limb bud on the A-P axis, determines the digit identity of the limb using a morphogenetic gradient
Polarizing region
Migration of germ cells in Mouse, mammals, and reptiles
- Migrate from the posterior into the hind gut then finally to the gonadal precursor cells
- Mouse-primordial germ cells (PGC) migrate to the posterior end of the embryo above the primitive streak
- Mammal germ cells migrate through the hind gut into the genital ridge
- Reptiles- send their germ cells from the head into the bloodstream
Somite derivative that gives rise to the vertebrae and ribs
Scleretome
Signal for abaxial muscle development
BMP4 signals from the lateral plate mesoderm
Draw the different cell types of a xenopus based on germ layer specifications
bind BMPs thereby preventing binding to their receptors, effectively blocking BMP signalling leading to neural development.
Noggin and Chordin
convergence of cells in the development of the zebra fish embryo along the animal pole that produces the elongated fish like shape
convergent extension
Formed when somites develop alone
Mesenchyme
Comm mutants
no crossing occurs at all. Comm’s function is to prevent robo from reaching the growth cone.
What does the red and green dots represent in this image and what does this signal cause?
Red: chordin/noggin being produced from the spemann organizer
Green: BMP-4
Chordin and noggin block BMP-4 allowing for neurnal tissue to form from the ectoderm
induces limb buds
FGF-10
Forms the Notochord
Cells that are part of the Spemann organizer at the beginning of
gastrulation enter the embryo during gastrulation and eventually
differentiate into notochord
What becomes of the cells that develop in the Blastocyst
Internal cells→ embryo and amnion
trophoblast cells→placenta and chorion
How is the D-V axis formed in drosophilla wings?
Wingless acts as a morphogen like dpp, required to form wings (d/v barrier)
Gastrulation in mouse
- Epiblast cells begin to move towards the primitive streak
- Primitive streak spreads out anteriorly and laterally to form the mesoderm between the visceral endoderm and ectoderm
- visceral ectoderm is replaced by definitive ectoderm
- Primitive streak continues until it reaches the bottom of the cup shape and forms a node (analogous to hensons node in chicks) which will later develop into the notochord
How are the layers of the neural tube created?
- Neurons are born in the ventricular zone and move outward to along radial glia to reach the outer surface
- Neurons crawl past each layer in succession as they move towards the outer surface
Cas-9
Cas9 encodes a nuclease that cuts DNA at a precisely defined point complementary to the sequence of a short ‘guide RNA’ that is part of the enzyme
out shoot of the axon’s body that utilize fillapodia to screen the environment and determine direction of growth
Growth cone
cavity the forms in between the yolk and embryo during chick development
subgerminal space
How is the A-P axis patterned for a limb
Morphogenetic gradient induced by the polarizing region
triggers the transition into floral development when the environmental signals are correct
LFY
Lithium and Cortical rotation duplications
- LiCl mimics wnt signalling through blocking of B-catenin degrading machinery allowing the signal to be utilized in absence of signalling pathway
Midbrain- hindbrain organizer
Organizer which divides the Otx/GBX regions into 4 distinct patterns
Attractive and repulsive cues in Neuronal movement
Unc-6 and Unc-40= attraction
Unc-6, Unc-40, and Unc-5= repulsion of the neuron
Floor plate also acts as a guidance cue
Moves into the flower bud apex to trigger flower development. activates
together with FD and LFY floral meristem identity genes like AP1.
FT
portion of the brain responsible for motor coordination, motor learning, balance and posture control, timing and rhythm of movements, ‘error correction’ of movement
Cortex
How is a limb specified as hind or forlimb
- FGF10-will work with either
- Tbx5- Forelimb
- Tbx4-Hind limb
form when with dorsal neural tube or ectoderm
Striated muscles
BMP-4
Promotes epidermal development and blocks neuronal development
3 steps involved in embryo development
- Cleavage
- Implantation
- Gastrulation/ turning
Function of Otx and GBX2
Otx- Signal the forebrain
GBX2-signals the hind brain
point along which the ingression of a chick embryo occurs, cells will move into the subgerminal cavity during this step
Primitive streak
Specialized cells which help guide the direction of axon development
Guideposts
Describe the two driving mechanisms of somite formation
FGF gradient- forms in high concentration at the posterior towards low concentration in the anterior. Important in forming boarders between Somites
Clock mechanism- every 90 minutes during somite formation genes will be expressed that move anterior to posterior leading to boundaries in the somites
Progress zone model
Identity of a portion of a limb is dependant on the amount of time spent in the progress zone
Name the 4 different signal types a neuron can be given
1) Chemoattraction
2)Chemorepulsion
3)Contact attraction
4)Contact repulsion
How is ectoderm and endoderm specified in a xenopus
In early embryo Animal cells form the epidermal cells where as vegetal cells form the endoderm
Proximal-distal patterning of limbs two models
1)Progress zone model
2)Two signal model
Forms the dermis
dermotome
Placenta
supply fetus with nutrients and oxygen, remove metabolic waste products (including
CO2), produce hormones (gonadotropins, steroids), prevent immunological rejection of the fetus, provide antibodies to help prevent infections of the newborn
Forms the trunk muscles
myotome
Forms cerebellum that is smaller disorganized, and improperly layered
Reeler mutatant
Signal for myotome development
Wnt signals from dorsal neural tube which activate the transcription factors MyoD, Myf-5
Turning step in mouse
- epiblast turns inside out so umbilical cord faces outer surface
- Embryo can now be covered in aminion
How is ectoderm diffrentiated into epidermis and neuronal tissues?
Inducing event for neuron development is gastrulation.
Dorsal ectoderm will form neural tissue, ventral ectoderm will form epidermis
BMP-4 -blocks neuron development
chordin/ noggin- produced by spemann organizer and blocks the effect of BMP-4 on the dorsal side
point along which gastrulation begins opposite to the site of sperm entry on the oocyte
Blastopore
Signals for proximal/distal patterning in developing limb bud, without limb development stops
apical ectodermal ridge
How are neuroblasts formed in drosophilla?
Neuroblasts start as a cluster in the neuroectoderm and express genes like scute and achete
Delta/Notch signalling initially down regulate scute and achete genes
This leads to lateral inhibition of neighbouring cells as Delta/notch work to down regulate genes while scute and achete act as enhancers to this down regulation signal
Early cleavage pattern in asicdians
- First cleavage is along the D-V axis followed by A-P axis
- Has an animal and vegetal half
