THE CONTROL OF EMBRYONIC HEMOGLOBIN SYNTHESIS
FRED H. WILT
Department of Zoology, University of California, Berkeley, California
I. Introduction
89
II. Formation of Hemoglobin
90
A. Erythropoiesis
90
B. Chemistry of Hemoglobin
91
C. Biosynthesis of Hemoglobin
92
D. Heterogeneity of Hemoglobin
97
E. Shift from Embryonic to Adult Hemoglobin
102
III. Embryology of Hemoglobin Formation
106
A. Amphibia
106
B. The Chick
108
IV. Control of Embryonic Hemoglobin Formation
114
A. Studies with Metabolic Inhibitors
114
B. Stimulation of Hemoglobin Synthesis
119
V. Conclusions
120
References
122
I. Introduction
A common introduction to developmental biology often attempts to
define "differentiation." Efforts to clearly state the questions to be
addressed to the embryo are still current, and one often hears discussions
about this or that "key" to differentiation. Perhaps the idea of a "key"
to differentiation should be suspect, for it ignores the fact that differentiation is a progressive change, composed of many interacting processes. Different criteria for identifying the stations marking the progression may be chosen, or the length of the journey may be arbitrarily
delimited, but in all but the narrowest intervals of time or space interacting processes are involved. One lesson for the student of developmental
biology is made amply clear by recent advances in molecular biology:
in most instances the nuclear genetic repository of different cells in a
given organism is probably identical, i.e., the sequence of bases in the
DNA is probably invariant; but the phenotypes of an organism's cells
may vary widely, in a more or less stable way. This can only be accomplished ultimately by control of expression of the information in the
89
FRED H. WILT
Department of Zoology, University of California, Berkeley, California
I. Introduction
89
II. Formation of Hemoglobin
90
A. Erythropoiesis
90
B. Chemistry of Hemoglobin
91
C. Biosynthesis of Hemoglobin
92
D. Heterogeneity of Hemoglobin
97
E. Shift from Embryonic to Adult Hemoglobin
102
III. Embryology of Hemoglobin Formation
106
A. Amphibia
106
B. The Chick
108
IV. Control of Embryonic Hemoglobin Formation
114
A. Studies with Metabolic Inhibitors
114
B. Stimulation of Hemoglobin Synthesis
119
V. Conclusions
120
References
122
I. Introduction
A common introduction to developmental biology often attempts to
define "differentiation." Efforts to clearly state the questions to be
addressed to the embryo are still current, and one often hears discussions
about this or that "key" to differentiation. Perhaps the idea of a "key"
to differentiation should be suspect, for it ignores the fact that differentiation is a progressive change, composed of many interacting processes. Different criteria for identifying the stations marking the progression may be chosen, or the length of the journey may be arbitrarily
delimited, but in all but the narrowest intervals of time or space interacting processes are involved. One lesson for the student of developmental
biology is made amply clear by recent advances in molecular biology:
in most instances the nuclear genetic repository of different cells in a
given organism is probably identical, i.e., the sequence of bases in the
DNA is probably invariant; but the phenotypes of an organism's cells
may vary widely, in a more or less stable way. This can only be accomplished ultimately by control of expression of the information in the
89