close

Вход

Забыли?

вход по аккаунту

?

Miért nehéz az egyedfejlődés problémája?

код для вставкиСкачать
The problem of development
Eörs Szathmáry (Alpbach 2005)
Collegium Budapest
Eötvös University Budapest
What’s this?
Let’s take another look!
Aggregation of the slime mold
пЃ®
пЃ®
The amoebae gather into a focus
Individual cells become bipolar
Propagation of the cAMP signal
and chemotaxis
пЃ®
пЃ®
Central cell emits a
dose of cAMP then it
rests for a while
Neighbouring cells
creep toward the
signal while they also
release a dose of
cAMP
Formation of Dictyostelium
fruiting body
пЃ®
пЃ®
In the slug pre-stalk
cells are first
Finally pre-spore cells
creep to the front
Why is the problem of
development so difficult?
пЃ®
We do not build developing machines:
physiology is „easy”, embryology is
„difficult”
Preformation versus epigenesis
пЃ®
пЃ®
Homonculus in the
sperm
Epigenetics:
complexity truly
increases
Self-assembly of the virus capsid
пЃ®
Subunits are composed of proteins
The process of aggregation
Formation of
the anteroposterior axis
of Drosophila
Do the genes programme
ontogenesis?
In a sense yes, BUT
пЃ® A bag of elephant proteins is not an
elephant
пЃ® Structure that self-assemble
пЃµ Virus particles
пЃµ The formation of sponges
пЃ® Limitations of the jigsaw puzzle principle
пЃ®
Wave-like properties of development
Wave forms are largely independent of
chemical composition
пЃ® Animal coat patterns (zebra, tiger, etc.)
пЃ® BUT altered genes can alter the shape of the
elephant
пЃ® Somehow molecules determine form even if
they do not self-assemble
пЃ® BUT HOW?
пЃ®
The lesser know work of Alan
Turing
пЃ®
пЃ®
пЃ®
пЃ®
пЃ®
English mathematician
Breaking of the german
code
Creator of the „universal
Turing machine”
His relevant paper:
Philosophical
Transactions of the Royal
Society (1952)
What is behind animal
coat patterns?
Theory of a chemical standing wave
пЃ®
пЃ®
пЃ®
пЃ®
пЃ®
Two compounds: an
activator and an inhibitor
The activator helps its
own formation
Inhibitor inhibits the
formation of the activator
Both compounds degrade
Inhibitor diffuses much
faster
A kГ©miai ГЎllГіhullГЎm
пЃ®
пЃ®
пЃ®
пЃ®
In a well-stirred medium both concentrations reach
equilibrium
If the solution is not stirred, then a positive fluctuation in
activator concentration will enhance itself
Fluctuation is due to chance
Inhibitor concentration also rises, but its higher diffusion
rate decrease the amplitude
The coat of a fish
пЃ®
пЃ®
Growth as well as REGENARATION seems to
follow a Turing mechanism
Reaction-diffusion systems
Wolpert: a „French flag”
A simple model of
pattern formation
Positional information and
pattern formation
пЃ®
пЃ®
Each person has a
specific seat in the
stadium
In each seat a specific
poster must be shown
Hair patterns in Oncopeltus as
indicator of polarity
пЃ®
пЃ®
Hairs point backwards on the cuticule
Removal of segment boundary reverses the
direction of hair growth
Development of the chick limb
пЃ®
The zone of polarizing activity (ZPA) directs the
formation of the order of digits
The effect of ZPA
Prepattern and consequence
пЃ®
Morphogen is the sonic hedgehog protein
Again the axis
of Drosophila
The expression of maternal
bicoid mRNA
пЃ®
Both mRNA and
protein can be
visualized by
appropriate
compounds
Determination of the 2nd evenskipped (eve) stripe
пЃ®
пЃ®
пЃ®
Bicoid and hunchback
proteins activate
Giant and KrГјppel
inhibit
Not too elegant!
Gene expression and pattern
пЃ®
Combinatorial
determination
VizsgaidЕ‘pontok
JanuГЎr 7, 14, 21, 28 KEDDEK, SzabГі
JГіzsef terem 10-12 Гіra
пЃ® JanuГЎr 9, 16, 23 CSГњTГ–RTГ–KГ–K, SzabГі
JГіzsef terem
пЃ®
Документ
Категория
Презентации
Просмотров
3
Размер файла
8 006 Кб
Теги
1/--страниц
Пожаловаться на содержимое документа