Study Questions 3-4 Flashcards
When are A-P and D-V axes specified during Drosophilia development
Determined during oogenesis, before fertilization
When are A-P and D-V axes specified during C.elegans developent
a-p axis is determine by site of sperm entry and d-v axis by formation of AB found cells
What is the difference between the two different types of blastoderm formed during drosophilia development
syncytical blastoderm- all nuclei contained in common cytloplasm
cellular blastoderm- all the cells are arranged in a single layerd jacket around yolky core of the egg
what are the types of genes invovled in determination of anterior-posterior axis in drosophillia
bicoid- fucntions as a transcription factor to activate anterior specific gap genes (hunchback)and a repressor to suppress posterior specific gap genes(caudal)
nanos- block translation of hunchback and upregulates caudal
What are the bicoid and nanos mRNAs produced during drosophilia oogenesis and where are the localized
Produced and secreted by nurse cell
Bicoid mRNA localized in anterior and nano mRNA
Nanos mRNA secreted by posterior ovarian nurse cells localized to posterior
What are the major posterior determinants in early drosophila development
Nanos and caudal
Define homeotic genes
act as selectors- activate the construction of segment-specifc traits like wings and legs
How is the dorsal-ventral polarity determined in the Xenopus embryo
sperm entry determines dorsal-ventral axis, which is liked to anterior-posterior axis determination
What are the two most important purposes of the balstocoel?
Permits cell migration during gastrulation and prevents early cell-cell interactions
Define regulative development
celld develop based on their locations in the embryo
define autonomous development
determination of cell fate acquired by cleavage, indepedent of interactions with neigbouring cells
Define Dorsal blastopore lip
location of the involuting marginal zone cells of amphibian gastrulation, acts as the center of differentiation
define spemann’s organizer
the dorsal lip cells of the blastopore and its derivatives (pretty much the same as blastopore lip), induces development of the nervous system
Define Nieuwkoop center
doral most vegetal blastomeres of xenopus blastula, induces the spemanns organizer
What is b-canenin
A transcription factor and important in specifying Nieuwkoop center
How does the amount of yolk influence cleavage in birds?
Discoidal meroblastic cleavage, embryo forms a blastodisc on top of the yolk
Have teloecithal egg cells, with the yolk concentrated at one end
Define primitive streak
formed by cells accumulating in the middle of the bird embryo, undergoes convergent extension
Define primitive groove
depression forms in the primitve streak and migrating cells pass through
Define hensens node
a funnel which migrating cells pass into the blastocoel, first site of gastrulation and located at the anterior of the primitive streak, analog spemanns organizer, IN AMPHIBIANS!
What are the first cells which are passing thorugh the primitive streak during gastrulation
endodermal precursors, undergo a transformation as the streak elongates towards the head
What is the chicken equivalent to the Xenopus Spemann organizer
Hensens node
What is the chicken equivalent to the amphibian blastopore lip?
PMZ, posterior marginal zone
What are the five characteristics of mammalian early cleavage?
1) division very slow
2) orientation of blastomere cleavage varies, second cleavage undergoes rotational cleavage
3) division are not necessarily synchronic
4) mammalian genome activated early in cleavage
5) compaction when the blastomeres huddle together
Define blastocyst
mammalian analog of the blastula
What is the role of trophoblast during embryonic implatnation
Role is to contribute to the further digesion of the uterus and formation of the placenta
What is the chorion
the embryonic portion of the placenta
What is formed during the first segregation of ICM? What is this structure called?
The hypoblast and epiblast, form the bilaminar germ disk.
What part of the bilaminar germ disk will develop into the embryo properly?
The epiblast
