Chapter 8 Flashcards
After the egg has been fertilized and metabolism activated,_______ and _______ begin
cleavage and gastrulation
_______ begin to form during gastrulation
body axis
Model invertebrates display type I embryogenesis:
- immediate activation of _______ genes
- rapid specification of _______
- relatively small number of cells at the start of _______
1) zygotic
2) blastomeres
3) gastrulation
What are the 4 model invertebrates?
1) snails (gastropod mollusks, protostome)
2) C. elegans (nematode, protostome)
3) Sea Urchins (echinoderms, dueterostome)
4) ascidians (tunicates, dueterostome)
Model invertebrates are:
1) easy to maintain in _______
2) short _______ time
3) Large numbers of _______ in each generation
4) easy genetic and surgical _______
1) lab
2) generation
3) offspring
4) modification
______: animals that gastrulate
metazoan
_______: basal phyla that have only 2 germ layers
diploblasts
_______: have mesoderm, third germ layer
triploblasts
diploblasts lack a true _______ and have ectoderm and endoderm
mesoderm
Triploblastst are _______ meaning they show bilateral symmetry
bilaterians
In protostomes, the blastopore becomes the _______
mouth
In protostomes, coelom forms through _______
schizocoely
Describe the process of schizocoely?
hollowing out solid core cells (mesoderm) to form coelom
_______: organisms that molt their external skeleton
ecdysozoans
- protostome
_______: display spiral cleavage and common trochophore larval pattern
lophotrochozoans
- protostome
What are the 4 groups of animal phylums that represent protostomes?
1) Mollusks
2) annelids
3) nematodes
4) arthropods
In deuterostomes, the blastopore becomes the _______
anus
In deuterostomes, coelom forms through _______
enterocoely
Describe the process of enterocoely
extending mesodermal pouches from the gut form coelom
Lancelots and tunicates do not have a backbone, but their larvae have _______
notochords and pharyngeal pouches
What are the 5 “phylums” that represent deuterostomes?
1) echinoderms
2) hemichordates
3) cephalochordates
4) tunicates
5) vertebrates
- 3,4,5 are chordates
Snails undergo _______, _______ cleavage
spiral holoblastic
- protostome
In spiral cleavage, blastomeres touch one another more closely. They sit in _______ of the nearby cells
grooves
- most thermodynamically stable arrangement
_______: blastula with very small blastocoel or no blastocoel
stereoblastulae
- snails has fewer cells than sea urchins
In snails, R/L axis is determined by the expression of _______ family paracrine factors
nodal
In snails, the first two cleavage planes are nearly _______ producing 4 large blastomeres
meridional
- down the middle
In snails, subsequent divisions after the first 2, are unequal, producing _______ (towards the animal pole) and _______
micromeres
macromeres
In snails, the angle of cleavage planes in mitotic apparatus is determined by cytoplasmic mRNA provided to the oocyte from the _______ cells
mother’s
- maternal affect
In Lymnaea peregra, this direction of coiling (LvR spiral) is controlled by alleles of the _______ gene
formin
Formin mRNA encodes a protein that binds to _______ and helps align the cytoskeleton
actin
Formin mRNA is _______ positioned as early as the 2-cell stage
asymmetrically
In snails, mothers with dd carry a homozygous frameshift, the mRNA for Formin is rapidly _______ and can’t be donated to the egg cytoplasm
degraded
_______ coiling: opening to the right
It is caused by what allele?
Dextral
- (D = dominant allele)
_______ coiling: opening to the left
It is caused by what allele?
Sinistral
- (d = recessive allele)
In order to construct a fate map for snails, scientists:
1) injected large _______ conjugated to _______ dyes into specific micromeres then monitored them
2) _______ of developing embryos
polymers; fluorescent
live imaging
- confirmed that protostome
the morphogenic determinants in snails all initiate gastrulation at the _______ pole very early, when only a few dozen cells have formed
vegetal
- autonomous specification
In snails, mRNA’s for some TF’s and paracrine factors partitioned by their association with certain _______
What mechanism allows this?
centrosomes
- allows for mRNA to be partitioned
- shape formed by 3’UTR
In spirally-cleaving embryos, a unique mechanism of positioning _______ determinants during cell divisions occurs
endomesodermal
Spirally cleaving embryos extend a bulb of _______ from one cell prior to and during division and then reabsorb it after division
cytoplasm
Extension of a bulb of cytoplasm creates a _______
tre-foil stage embryo
A tre-foil stage embryo contains:
1) cleavage orientation in _______
2) _______ and _______ formation
3) specifying _______ axis
4) guiding _______ gland and _______ inductive interactions
1) D blastomeres
2) mesodermal and intestinal
3) dorsal/ventral
4) shell; eye
The bulb of cytoplasm in a Tre-foil stage embryo is called a _______
Polar-lobe
in snails, the _______ is required for heart and gut formation
mesentoblast
- (4d blastomere)
- connected to polar lobe
What are the 3 major determinants acting in the process of polar-lobe creation?
1) TF
2) translation
3) signaling pathway
1) b-catenin
2) nanos
3) Notch
All cell fates have been largely determined by inductions from the _____ series of blastomeres
D
- the organizer
in snails, the _______ forms @ ___-days post fertilization as a separate hole not associated with the blastopore
anus
12
In snails, gastrulation occurs through what two gastrulation mechanisms
1) epiboly
2) invagination
