1. Fate Maps
Defined as a chart or surface mapping
showing the fate of an early embryo in
blastula stage called Fate Maps.
The number of cells marked into different
areas
Which develop into a particular organ or
organ system.
Methods of Construction of Fate
Maps
1. Using natural markings
2. 2. Using artificial markings
1. Natural Markings: some ascidians, Styela,
Ciona, Cynthia , the cytoplasm of the
fertilized eggs have natural colour differences
in various regions, 4 regions of the egg can
be distinguished from the cytoplasm, they
are –
(a) Upper hemisphere with clear cytoplasm
represents epidermal ectoderm called
ectoplasm
3. (b) Postero ventrally the yellow coloured area
which is the prospective mesoderm, called
mesoplasm
(c) Antero dorsally grey coloured area with 2
developmental prospects Upper neural
ectoderm called the neuroplasm & the lower
one which form the Notochord called the
chordaplasms
(d) A vegetal area of dark grey yolky plasm is the
prospective endoderm and called endoplasm
4. 2. Artificial markings: In some animals natural
colour differentiation of egg cytoplasm does not
occur , therefore some artificial methods
have been used to construct fate maps.
(a) Vital staining marking methods: discovered by
Wather Vogt (1925),using vital dyes which stains
the cells & do not interfere with normal process
of development. The stain carriers are used like
agar , cellophane, stained with dyes like Nile blue
sulphate, Neutral red, Janus green,Bismark brown
etc pressed against the chosen area , dyes
diffuses into the blastomeres & helps in the
5. construction of map of prospective organs
forming areas. E.g Amphioxus, frog, chick &
mammal.
(b) Carbon particle marking method:discovered
by Spratt (1946), a tiny particles of carbon
applied to the surface of an embryo, which
sticks to the egg surface & used as markers ,
their movements helps in the construction of
fate maps.
6.
7. (C) Radioactive marker method:Recent
method,the radio active markers like tritiated
Thymidine or cells of different species with
different staining properties grafted to the site
of study.
Significance
Helps in understanding gastrulation.
