ROLE OF mRNA IN EMBRYONIC DEVELOPMENT
131
(c) Stage 26-28
-32
"C II hr
^P^^'X ! h r ° '*C 4 hr 30 J
40
80
120 160 200 240
40
80
120 160 200 240" 920
RNA/DNA
FIG. 10. Saturation of DNA with RNA from different stages [mature eggs (a);
gastrulae (b); tail-bud embryos (c); differentiated
tadpoles (d)], labeled for
various lengths of time. In experiment (a), the eggs were labeled by injecting
3 2
P
into the female 1 day before ovulation. In each experiment, 10-20 jig of DNA were
incubated with increasing amounts of labeled RNA. The numbers shown in
ordinates refer to the percentage of DNA that can be saturated by the RNA of
each stage.
observation will give information on the stability of mRNA present at
various stages. It will be discussed in detail in the next section.
V. Stability of Messenger RNA Present at
Different Stages of Development
A. Chase Experiments
When RNA from embryos labeled with
3 2
P from the beginning of
development is hybridized with increasing amounts of DNA, the percentage of radioactivity bound to DNA increases according to a complex
% Saturation
3i
2
j
i •!
1 0