Definitions Flashcards
acrosome
egg (ovum) vs. oocyte
zona pellucida
vitelline membrane
cumulus
cortical granules
polyspermy
ampulla
capacitation
just all of them lol needed this here so i didnt have to go back and forth between the powerpoint
acrosome
-In front of the nucleus of a sperm (cap of nucleus)
-derived from the golgi (modified secretory elements) : basicially during spermatogenesis golgi secretes enzymes that end up coming together to form the golgi and once this occurs, the golgi isnt there no more
-so the acromosome contsins enzymes and complex sugars
Egg (ovum) vs Oocyte
Egg: female gamete that is able to bind sperm and be fertilized
OOcyte: A developing egg that is not able to bind sperm yet or be fertilized (essentially the precursor to egg)
What are the five stages of meiosis
1)leptotene –condensed chromatin becomes apparent
2)zygotene – homologous chromosomes pair up and a structure called the synaptonemal complex forms between the homologous chromosomes
3)pachytene – “thickening” of chromosomes and genetic recombination (aka crossing over) – paired chromosome structure is called a “tetrad”
4)diplotene – sister chromatids of homologous chromosomes separate from each other as the synaptonemal complex breaks down – crossover sometimes visible as chiasmata
5) diakinesis - a further condensation of the chromosomes and, simultaneously, a further separation of the chromatids takes place that, however, still hang together at the chiasmata.
zona pellucida
-extracellular envelope/ matrix that is THICK
-ONLY FOR MAMMALS
What is an extracellular matrix/envelope?
-fibrous layer around the egg: often associated with sperm recognition
Look at slide 37
vitelline membrane
-extracellular matrix of invertebrates
-thin tough layer
-many have a glycoprotein meshwork (egg jelly) surrounding the vitelline envelope (attracts or activates sperm)
(jelly coat)
What is an extracellular matrix/envelope?
-fibrous layer around the egg: often associated with sperm recognition
Look at slide 37
cumulus
-outside of MAMMALIAN CELLS cause it is found on the outside of zona pellucida
-a layer of ovarian follicle cells that were nurturing the egg at the time of release from the ovary
-innermost cumulus cells are called corona radiata
Look at slide 37
cortical granules
-membrane bound (golgi derived) containing enzymes, mucopolysaccharides, adhesive glycoproteins, hyaline glycoproteins,
-homologous to acromosome of sperm (however 1 acromosome per sperm vs 15,000 ortical granules per egg)
found underneath the cell membrane along with actin which polymerizes into actin microfilaments at fertilization
can fusion occur anywhere on sea urchin
YEP but for other people it is isite specific
polyspermy
multiple sperm entering an egg
-results in too many sets of chromosomes
-ie triploidy means 3 sets, and this leads to genetic imbalance which could lead to developmental failures (not always, things like blueberries are triploid)
Ampulla
site where fertilization occurs
oviduct, distal to uterus and near ovary where fertilization takes place
provides great environment for fertilization and helps transport gametes
Capacitation
-set of changes that allow sperm to become able to fertilize egg (become primed to undergo acrosomal rxn and primed to fuse to cell membrane)
when sperm become mature during voyage ti oviduct, if not wont be able to fertilize egg
-sperm released during ejaculation ar able to move but they vannot yet fertilize egg, need to be matured in reproductive tract
-this is because sperm is quiescent transcriptionally and translationally (means dormant) sothey rely on post translational modifications such as phosphorylation of proteins to control maturation process
-this occurs as sperm comes in contatt with natural conception lubrication
-this needed to be understood to have successful ivf treatments and stuff
animal hemisphere
vegetal hemisphere
cortical rotation
marginal zone
vegetal rotation
radial intercalation
convergent extension
blastopore
Nieuwkoop centre
organizer
things for xenopus
animal hemisphere
-darkly pigmented
-non-yolk area
-upper half
-During embryogenesis: cells divide rapidly
vegetal hemisphere
-pale region
-yolk heavy
-serves as food for developing embryo
-slow division, less movement
cortical rotation
cortex: outer layer of egg, containing membrane, cytoskeletal components, rough er
when sperm enters: cortex loosens from the inner yolky core. Develops shear zone (yolk free area between cortex and core)
During first cell division: cortex rotates 30 degrees , so vegetal cortex is displaced from sperm entry towards FUTURE dorsal area
-happens at the same time as translocation of maternal dorsal activity also from vegetal pole to future dorsal area
How does it turn:
Microtubule arrays appear mid 1st cycle, cortical and dorsalizing activity relies on this
-plus end away from sperm site of entry
-allows these to move towards dorsal anterior end
w/o microtubules, no dorsal anterior structures
RESULTS: gray crescent (inner gray cytoplasm where gastrulation starts)
without cortical rotation:dorsalizing activity remains in vegetal region where it is not active, dorsalizing activity needs to be relocated to be active
marginal zone
In amphibians: Where gastrulation begins, the region surrounding the equator of the blastula, where the animal and vegetal hemispheres meet.
vegetal rotation
During frog gastrulation, internal cell rearrangements place the prospective pharyngeal endoderm cells adjacent to the blastocoel and immediately above the involuting mesoderm.
radial intercalation
Radial intercalation refers to the movement of cells from deeper layers of a tissue (radial layers) into more superficial layers, resulting in the thinning and expansion of the tissue.
-essentially the integration of several cell layers into one
ex: the involuting marginal zone (IMZ) and the noninvoluting marginal zone (NIMZ) are initially several cell layers deep and become one thin broad layer
convergent extension
-medial lateral intercalation of cells
-extends the post involution marginal zone
-polarized cell intercalation drives it (protrusion of cells to eachother, cadherin adhesion, actin myosin contractility)
-the medial lateral intercalation of cells in one axis and the elongation of cells in another axis
blastopore
-invagination of cells (slit-like blastopore)
-fo9und in dorsal region
-opening of the archaentron
Nieuwkoop centre
-dorsal most vegetal cells of the blastula
-induce formation of organizer
-signalling center opposite of site of sperm entry in xenopus
during cortical rotation: he vegetal cortex opposite the sperm entry point moves towards the animal pole.
This leads to the formation of a ‘signaling centre’ opposite the site of sperm entry known as the Nieuwkoop Centre.
This process leads to bilateral symmetry with the Nieuwkoop Centre at the midline separating right and left sides of the embryo.
Importance: set up the DV polarity in the blastula and ESSENTIAL for developemnt, 1st cleavage cuts through this
Signals from this center are needed to develop dorsal structures
organizer
-the dorsal lip of the blastopore
-derived from grey crescent
Function: instruct the formation of the embyronic body axis
-also protect ectoderm from bmp signalling, allowing it to differentiate into the neural tissue (BMP changes ectoderm into epiderm, so organizer protects it from it, making it be neural tissue which is the default)
examples: noggin and chordin
gamete
genome
cleavage division
blastomere
zygote
morula
gastrulation
gastrula
enhancer
induction
competence
morphogen
commitment
specification
a) autonomous specification
b) conditional specification
c) syncytial specification
determination
holoblastic cleavage
meroblastic cleavage
invagination
involution
ingression
delamination
epiboly
archenteron
convergent extension
deuterostome
protostome
General development biology
gamate
a specialized reproductive cell through which sexually reproducing parents pass chromosomes to their offspring (a sperm or an egg
genome
the complete DNA sequence of an individual organism
cleavage division
a series of rapid biotic cell divisions following fertilization in many early embryos
- it divides the embryo without increasing its mass
blastomere
a cleavage-stage cell resulting from mitosis
zygote
a fertilized egg with a diploid chromosomal complement in its zygote nucleus generated by fusion of the haploid male and female pronuclei
morula
vertebrate embryo of 16-64 cells
- proceeds the blastula/ blastocyst stage
gastrulation
a process involving movement of the blastomer of the embryo relative to one another resulting in the formation of three germ layers of the embryo
hey buddy
gastrula
a stage of the embryo following gastrulation that contains the three germs layers that will interact to GENERATE THE ORGANS OF THE BODY
enhancer
DNA sequence that controls the efficiency and rate of transcription from a specific promoter
induction
the process by which one cell population influences the development of neighbouring cells via interactions at close range
competence
the ability of cells or tissue to respond to a specific inductive signal
morphogens
substances that, by their differing concentrations differently specify cell fates
commitment
a state in which a cells developmental fate has become restricted even though it is not yet displaying overt changes in cellular biochem and function, it is more limited to what it will become but won’t necessarily look different
- two stages of commitment:
1. specification
2. determination
specification
first stage of commitment of cell or tissue fate during which the cell or tissue is capable of differentiating autonomously (by itself) when placed in a neutral environment with respect to the developmental pathway
- at this stage cell commitment can still be reversed
autonomous specification (mosaic dev.)
- ## predominates in most invertebrates
conditional specification
- predominates in vertebrates
- is the process by which cells achieve their respective fates through interactions with other cells
- cleavage divisions are variable and fate assignment is flexible
- massive cell rearrangements and migrations precede or
accompany specification - known as regulative development: if a blastomere is lost the embryo can compensate
syncytial specification
- mostly in insects
- the interaction of nuclei and transcription factors which eventually result in cell specification, take place in a common cytoplasm
determination
the second and IRREVERSIBLE stage of cell or tissue commitment in which it is capable of differentiating autonomously even when placed into a non-neutral (such as when transplanted into another region of the embryo)
holoblastic cleavage
- greek holos = complete
- a cell division (cleavage) pattern in the embryo in which the entire egg is divided into smaller cells
- frogs and mammals
mesoblastic cleavage
- greek meros = part
- the cell division (cleavage) pattern in zygotes containing large amounts of yolk where only a portion of the cytoplasm is cleaved.
invagination
folding of a sheet (epithelium) of cells (like the indention of a soft rubber ball when it’s poked)
- type of cell movement during gastrulation (step 1)
involution
inward movement of an expanding outer layer so that it spreads over the internal surface of the remaining external cells
- type of cell movement during gastrulation (step 2)
ingression
migration of individual cells from the surface to the embryos interior.
- individual cells become mesenchymal (separate from one another) and migrate independently
- epithelial to mesenchyme transitions (EMT)
- type of cell movement during gastrulation (step 3)
delamitation
splitting one cellular sheet into two more or less parallel sheets.
- results in the formation of a new (additional) epithelial sheet of cells
- type of cell movement during gastrulation (step 4)
epiboly
movement of epithelial sheets (usually ectodermal cells) spreading as a unit (rather than individually) to enclose deeper layers of the embryo.
- can occur by cells dividing, changing shape or by several layers of cells intercalating into fewer layers (all three mechanisms usually used at same time)
archenteron
the primitive gut of sea urchin blastula
- formed by invagination of the vegetal plate into the blasteocel
convergent extension
a phenomena wherein cells intercalate to narrow the tissue and at the same time move it forward (think of traffic on a highway where several lanes merge into one)
- basically the archenteron becomes a long thin tube
- this involves cell shape change and cell migration
- cells become thinner and intercalated
deuterostome
animals which the blastopore will become the anus
- “mouth second”
protostome
animal which the blastopore will become the mouth
- “mouth 1st”
blastodisc
telolecithal
yolk syncytial layer
enveloping layer
deep cells
epiblast
hypoblast
embryonic shield
Balbiani body
fish
blastodisc
-yolk free cytoplasm found at the animal pole
(clear island of no yolk)
-aka cytoplasmic cap
-where meroblastic divisions occur, leading blastodisc to turn into blastoderm
-after fertilization, wave of ca cause contraction of actin cytoskeleton which moves the region to animal
Summary: Small region at the animal pole of the telolecithal eggs of fish and chicks, containing the yolk-free cytoplasm where cleavage can occur and that gives rise to the embryo.
-after cortical granule reaction, the chorion (vitelline envelope) lifts from the surface of the egg (makes fertilization envelope)
-cytoplasmic streaming due to actin myosin contractions (fromwave of ca) causes NON YOLKY CYTOPLASM at animal hemisphere
telolecithal
an egg in which the yolk is unevenly distributed, with most of the yolk concentrated at one pole of the egg,(vegetal pole), while the other pole, the animal pole, contains less yolk and more cytoplasm.
yolk syncytial layer
-a distinct cell layer of early blastoderm
layer between the blastodisc (non yolk part that divides mesoblastic divisions, specificlly the deeo cells) and the yolky layer
-occur during mid blastula transition. (cleavage 10)
-nuclei of yolksynticial layer comes from the margin cells of blastoderm
-induce mesoderm
enveloping layer
-found in early blastoderm stage
-outermost cell layer of blastoderm
-during epiboly, these cells spread over the yolk
-deep cells intercalate with these superficial cells to form this during gastrulation
-eventually joins to yolk synticial layer
deep cells
-cells located between the enveloping layer (EVL) and the yolk synticial layer
-cell layer in early blastoderm
epiblast
happens halfway in epiboly
thickening thorughout the margin part of Epibolizing blastoderm is called the germ ring
germ ring has two layers
1) epiblast
2) Hypoblast
Epiblast is the syperficial layer, upper layers of cells
hypoblast
inner layer of the germ ring
-internalizing vells at blastoderm margin also forms this
embryonic shield
-intercalation of the epiblast and the hypoblast on the dorsal side (forms this shield)
-thickening on the dorsal side (accumulation of cells on one part of germ ring)
-homologous to drosal lip of amphibians
-epiboly pauses while this shield forms
-once blastoderm margin covers entire egg, the shield converges anteriorly forming precursor to notochord and precordal plate (like blastopore lip in xeno)
Important for: dorsal ventral axis
-can convert lateral and ventral mesoderm (blood and connective tissue) into dorsal mesoderm (notochord and somites)
-can cause ectoderm to become neural rather than epiderm
Balbiani body
-mitochondrial cloud
-associated with maternal mrna locatlization
-visible in early stages of growth
Lampbrush chromosomes
-special type of chromosome found in growing oocytes
-transform into lampbruhs form during diplotene stage of meiosis
-come about since zebrafish are highly transcriptionally active during growth phase
micropyle
-hole in vitelline envelope that sperm gies through during fertilization
-comes about since one follicle cell v(what secretes the envelope) is in contact with the envelope
compaction
inner cell mass
trophoblasts
trophectoderm
cavitation
blastocyst
epiblast
hypoblast
bilaminar germ disc
embryonic epiblast
amniotic cavity
cytotrophoblast
syncytiotrophoblast
trophoblastic lacunae
amniotes/mammals
compaction
-unique for mammalian cleavage
-mediated by e cadherin
-occur at 8 cell stage
-blastomeres become tightly oacked because they changed adhesive properties (more e cadherin make them bind more)
-cell cell junctions are formed
inner cells have gap junctions which allow small molecules to move between them
outter cells have tight juctions, which prevent inner cells with exchanging things with outside environment
inner cell mass
occurs in 16 cell morula (goes from 8 cell to 16)
-small group of internal cells that will produce the embryo
trophoblasts
in the 16 cell morula
-the large group of external cells (external to the inner cell mass)
-these cells will become the trophectoderm
-these cells do not contribute to formation of actual embryo but form the CHORION (outer layerthat surrounds embryo, which ensd up forming placenta)
they are the external cells that also bind the embryo to the uterus (task to make these is important for mammal development so that it can stick to the uterine wall (not elsewhere)
once at uterine wall, these have L-selectin on surface of cells to bind to endometrium sulfated polysaccharides of the uterine
trophectoderm
-this differentiation is the first differentiation event of mammalian embryogenesis
cavitation
Cavitation: A process whereby the trophoblast cells secrete fluid into the morula to create a blastocoel. The membranes of trophoblast cells pump Na+ ions into the central cavity, which draws in water osmotically, thus creating and enlarging the blastocoel.
As the blastocoel forms through cavitation, the ICM becomes positioned on one side of the trophoblast cells – this type of blastula is known as a blastocyst.
blastocyst
Cavitation forms the enlarging of the blastocoel… as it forms, the inner cell mass gets positioned on one side of the trypoblast cells,
Cthis type of blastula is known as blastocyst
zona pellucida preents the blastocyst from sticking to tube wall (not uterine), eventually the blastocyst releases proteases to digest this and hatches from the zona pellucida, allowing it to bind to the uterine wall
epiblast (mammals0
cells of inner mass form two layers, another name for this inner cell mass is bilaminar germ disc
this is one,
seperates into two parts:
1) Embryonic epiblast: forms embryo proper
2)cells that line amniotic cavity: aminotic fluid fills here
hypoblast
Second part of inner mass cell (bilaminar germ disc)
delaminate to form a layer facing the blastocoel
bilaminar germ disc
inner mass cells derives 2 layers… epiblast and hypoblast
these two together are the bilaminar germ disc (once the inner mass cells form into these two, both of them together is no longer called hte inner mass cell but called this)
embryonic epiblast
a part of the epiblast (whic is a part of the bilaminar germ disc)… this is the part that turns in to the embryo (embryo proper) theother part of the epiblast turns into amniptic cavity
amniotic cavity
other part of the bilaminar germ disc, this is the part that fills with amniotic fluid that is a shock absorber and prevents dehydration
cytotrophoblast
-original tryphoblasts form a layer called this
-originally adheres to endrometrium layer
syncytiotrophoblast
-cells that are able to grow by nuclear division without cytokinesis form this
-furthers progression of embryo into uterine wall by digesting uterine tissue
-original tryphoblast cells turn into this thing
trophoblastic lacunae
Cytrotrophoblasts secrete paracrine factors that attract maternal blood vessels, and maternal vasucular tissue is DISPLACED by trophoblasts…
forming this
amniotes
amnion
chorion
allantois
discoidal meroblastic cleavage
area pellucida
epiblast
subgerminal cavity
area opaca
marginal zone
hypoblast islands
secondary hypoblast (endoblast)
posterior marginal zone
primitive streak
primitive groove
Hensen’s node
Ammonites/chicks
amniotes
vertebrates who’s embryos form an amnion
amnion
“water sac”
- a membrane enclosing and protecting the embryo and its surroundings amnionic fluid
- water sac provides protection from desiccation and mechanical shock
chorion
essential for gas exchange
allantois
stores waste and helps mediates exchange
discoidal meroblastic cleavage
- occurs in bird eggs
- cleavage only occurs in the blastodisc and doesn’t extend into the yolk
- blastodisc: a small amount of cytoplasm sitting atop a large yolk
area pellucida
a 1-cell thick transparent layer of deep cells from the centre of the blastoderm which shedded and died
epiblast
upper layer of area pellucida (forms part of the area pellucida)
subgerminal cavity
a space that sits between the blastoderm and the yolk
area opaca
surrounds the area pellucida and is the peripheral ring that does not shed deep cells
- its opaque
marginal zone
in-between thin layer of cells
hypoblast islands
delaminate (divided) area pellucida cells which are primary hypoblasts/polyinvagination islands
- forms hypoblast
- found beneath epiblast
secondary hypoblast (endoblast)
the pushing of the hypoblast islands anterior due to deep yolky cells of posterior margin migrates anterior beneath the epiblast
Koller’s sickle
a crescent shaped cluster of cells beneath the epiblast at the posterior margin
posterior marginal zone
signalling center that plays key role in the formation of primative streak and hypoblast
primitive streak
the first morphological sign of gastrulation in amniotes that first arises from a local thickening of the epiblast at Koller’s sickle
- defines AP axis of avian embryo
- goes from posterior to anterior
-
primitive groove
the depression formed within the primitive streak where migrating cells pass into the deep layers of the embryo
Hensen’s node
a funnel shaped depression anterior end of the primitive streak
- the frog organizer and the fish shield
neural plate
neural tube
neurulation (primary & secondary)
neural crest
cerebellum
spina bifida
neural crest early vs. late migration
melanocytes
ectoderm : neuraltion and neural tube
neuralation: formation of the cns and the formation of neural tube from the neural plate
neural plate
region of dorsal ectoderm so specified to become neural ectoderm
Low levels of BMP caues it to be this
High levels of BMP cause it to be epidermins
Intermediate levels: cause ectoderm to be neural crest cells
neural tube
neural plates folds into a tube in a process called neuralation
-precursor of the CNS
neurulation (primary & secondary)
Primary: FORMS FROM EPITHELIUM
-invagination and rolling up of a sheet of cells that seperate as a tube from the overlying epithelium
Steps:
1) FOlding of neural plate
2) elevation of plate
3)Convergence of folds: making the neural groove
4)Closure of neural groove to make the neural tube
Three products of primary neuralation:
1) Epidermis
2) neural tube
3) neural crest cells
Presence of N cadherin instead of E cadherin drive cell adhesion needed for neural tube closure and seperation of neural cells from epidermis
Secondary: FORMS FROM MESENCHYME
building a new neural epithelium from mesenchymal cell condensation and subsequent cavitation. (note: mesenchyme to epithelial transition)
-more common in tail
Both can occur in the same animal, complete neural tube forms when both are combined
look at pic o slide6
neural crest
Neural crest cells: become many cell types including the PNS and melanocytes
intermediate levels of BMP cause ectoderm to be this
-form where the neural tube and epidermis meet in primary neuralation
-sometimes called fourth germ layer
Cranial neural crest cells: bone plus neurons, glial etc
Trunk neural crest cells: no bones but has rest
cerebellum
Function: MOTOR COORDINATION
spina bifida
Failure to close the posterior neural tube results in this
Failure to close the neural tube is a problem…
open ends of the neural tube are reffered to as anterior and posterior neuropores…
What helps prevent:
Follate vitamins (B9: folic acid)
Not understood well but there is a folate binding protein expressed on dorsalmost area of neural tube at time of fusion
Found this out cause follate receptors in mouse cause more likely neural tube failure to close posterior end in mouse
Foods can also cause disruption to the follate receptors ie fungal contaminants ( act. as a teratogen) the mycotoxin is called fumonisin
neural crest early vs. late migration
early:Snail2 transcription factor down-regulates cadherin-6B, a cadherin enriched in premigratory neural crest cells.
Early cells follow a ventral pathway through the anterior part of each sclerotome (chunks of mesoderm that will eventually form vertebral cartilage); they will become sensory and sympathetic neurons, adrenomedullary cells and Schwann cells.
Late:Late cells follow a dorsolateral pathway to become melanocytes
melanocytes
pigment cells
notochord
paraxial mesoderm
somites
dermomyotome
sclerotome
limb buds
progress zone
Apical ectodermal ridge
zone of polarizing activity
Mesoderm
notochord
- develops from the dorsal most region of mesoderm
- chordamesoderm forms it
paraxial mesoderm
- forms the somites which will form the axial skeleton (vertebrae, ribs), all skeletal muscle and the dorsal dermis, tendons, joints and dorsal aortic cells
- somatic mesoderm
somites
segmental block or ball of mesoderm formed for paraxial mesoderm adjacent to notochord
- forms most but not all the axial skeleton (vertebrae, ribs), all skeletal muscle, and the dorsal dermis, tendons, joints, and dorsal aortic cells
- gives rise dermomyotome and sclerotome
dermomyotome
- derived from somite forming the late somites dermatome which forms the dermis and myotome which forms the skeletal muscle
sclerotome
- the second the derivative from from somite forming the late somites syndetome which makes the tendons and sclerotome which forms the vertebral body (bones and cartilage, ribs, dorsal aorta cells
limb buds
a circular bulge that will form a further limb
- formed by the proliferation of mesenchyme cells from the somatic layer of the limb field lateral plate mesoderm (the limb skeleton precursor cells) and form the somites (the limb muscle precursor cells)
progress zone
underlying mesoderm
- Wnt/Fgf10 found here
Apical ectodermal ridge
- found along the distal margin of the wing bud (the boundary between dorsal and ventral)
- critical signalling centre for limb development
- induced by mesoderm cells secreting Fgf10
- maintained through positive feedback loops after established where Wnt/Fgf8 is signalling in the ectoderm and Wnt/Fgf10 is signalling in the underlying mesoderm
- maintains the underlying mesoderm in a plastic
proliferative state – enabling elongation of the
limb in proximal/distal axis - maintains expression of molecules responsible
for the anterior-posterior limb axis (thumb to
pinkie - interacts with proteins that specify
anterior/posterior as well as dorsal ventra
zone of polarizing activity
- signals from the limb bulb that signal development of the limb along the anterior-posterior axis
- Sonic Hedgehog (Shh)
