Mammalian Cleavage Flashcards
Echinoderm/Amphibian: cleavage plane bisect than the second will be perpendicular to the first
holoblastic rotational
true or false
Mammal: bisect into two then the second: both are meridional
False (one is meridional, the other is equitorial)
-slow division and asynchronous
- embryo undergoes compaction
Blastocyst: equivalent of blastula
early expression of zygotic genes
holoblastic rotational (in mammalian cleavage)
what are the three characteristics of mammalian cleavage?
- asynchronous cleavage
- early midblastula transition
- compaction of blastocyst: peculiarity
where does oocyte gets fertilized?
Upper ⅓ of the fallopian tube
(hatches out of zona pellucida in the womb only)
which theory discusses the equivalence of blastomere nuclei
Weismann’s germ plasm theory
it states that gametes contains determinants which are abortion differentially into blastomeres which develop into different cell types
Weismann’s germ plasm theory
it talks about the possible source of differentiation of different blastocyst
-blind heterician
Weismann’s germ plasm theory
true or false
Weismann’s germ plasm theory states that the zygote, from being a single cell, when it divides the produce different blastomere, the cells don’t get different morphogenetic determinates that are differentially apportioned (that’s why fates are different)
False (the cells DO get different morphogenetic determinates)
what contradicted Weismann’s germ plasm theory
the nuclei that the blastomeres get during cleavage are actually equivalent
who experimented on newt zygote which, the results contradicted weismann’s germ plasm theory?
Spemann
on partially constricted newt zygote,
- 2 halves developed into normal embryos
- each cell contained the determinants for the whole embryo
what are the three experiments that contradicted weismann’s germ plasm theory?
- Spemann’s expt in newt zygote
- dragonfly : one of first of two nuclei fertilized egg was irradiated: a whole embryo still developed
- cloning experiments: first done in frogs
what can be learned after Weismann’s germ plasm theory was proved wrong?
the nucleus is not the source of differentiation of the fates of the cells
