294
CHARLES Ε.
WILDE
tions and maintains the cells in their proper differentiative pathway. It
is obvious to the most casual observer that the pathways of differentiation are highly varied, nor is their any a priori reason to assume that
differentiative events are in any sense similar chemical reactions.
Indeed, the reverse case is highly probable.
If the problem is approached from the level of the cell itself, dissecting
downward by all available means through the particulate components
of the cell, to macromolecules then to molecules, atoms and ions,
appears that there are several broad categories of phenomena into which
differentiative activities can be grouped. As will be seen the groupings
are not necessarily exclusive, but rather point to a series of initiator -
succedent phenomena at the molecular level. The classification then
depends on the identification of the initiator reaction of the series and
its morphological location within or without the cell.
Drawing on the wealth and precision of data from genetics, one is
led to consider that the genetic code as exemplified by chromosomal
deoxyribosenucleic acid serves as a complex series of initial cues the
response to which is signalized in the synthesis of specific protein
enzymes, perhaps through the mediation of ribosenucleic acid. The
specificity of the enzyme pattern in turn cues the response of the cell
along particular synthetic pathways and mediates the selection of
suitable substrates for further syntheses. The result of the synthetic
chain will be manifested in the form and function of the differentiated
cell. This type of 'one-way drive' has yet to be tested by exacting
experiments in 'reverse gear'. There are two areas of investigation
among vertebrates where 'reverse drive' in terms of the chemistry of
differentiative processes could be tested.
Barb keratin of the turkey is quantitatively different in terms of
amino acid residues from rachis or calamus keratin in the same animal.
Barb keratin of the turkey is chemically distinct from barb keratin of
goose (Schroeder and Kay, 1955). A possible 'reverse drive' experiment
would lie in the analysis of the chemical composition of the keratins in
feathers developing from transplants between the two types of fowl, or
between any fowl where the necessary antecedent organic chemical data
were known. The embryologist would expect each species to retain its
specific morphological feather pattern, but what of the chemical
composition of the keratins in the transplant, host or donor? Host amino
acid residues would indicate some externally enforced alteration of the
synthetic processes of the donor cells, while the maintenance of donor
chemical patterns would indicate that the genetic endowment of the
donor cells was able to cue proper syntheses even in the face of a faulty
or erroneous substrate pool.
The human heritable anaemias are in part categorized by minor
CHARLES Ε.
WILDE
tions and maintains the cells in their proper differentiative pathway. It
is obvious to the most casual observer that the pathways of differentiation are highly varied, nor is their any a priori reason to assume that
differentiative events are in any sense similar chemical reactions.
Indeed, the reverse case is highly probable.
If the problem is approached from the level of the cell itself, dissecting
downward by all available means through the particulate components
of the cell, to macromolecules then to molecules, atoms and ions,
appears that there are several broad categories of phenomena into which
differentiative activities can be grouped. As will be seen the groupings
are not necessarily exclusive, but rather point to a series of initiator -
succedent phenomena at the molecular level. The classification then
depends on the identification of the initiator reaction of the series and
its morphological location within or without the cell.
Drawing on the wealth and precision of data from genetics, one is
led to consider that the genetic code as exemplified by chromosomal
deoxyribosenucleic acid serves as a complex series of initial cues the
response to which is signalized in the synthesis of specific protein
enzymes, perhaps through the mediation of ribosenucleic acid. The
specificity of the enzyme pattern in turn cues the response of the cell
along particular synthetic pathways and mediates the selection of
suitable substrates for further syntheses. The result of the synthetic
chain will be manifested in the form and function of the differentiated
cell. This type of 'one-way drive' has yet to be tested by exacting
experiments in 'reverse gear'. There are two areas of investigation
among vertebrates where 'reverse drive' in terms of the chemistry of
differentiative processes could be tested.
Barb keratin of the turkey is quantitatively different in terms of
amino acid residues from rachis or calamus keratin in the same animal.
Barb keratin of the turkey is chemically distinct from barb keratin of
goose (Schroeder and Kay, 1955). A possible 'reverse drive' experiment
would lie in the analysis of the chemical composition of the keratins in
feathers developing from transplants between the two types of fowl, or
between any fowl where the necessary antecedent organic chemical data
were known. The embryologist would expect each species to retain its
specific morphological feather pattern, but what of the chemical
composition of the keratins in the transplant, host or donor? Host amino
acid residues would indicate some externally enforced alteration of the
synthetic processes of the donor cells, while the maintenance of donor
chemical patterns would indicate that the genetic endowment of the
donor cells was able to cue proper syntheses even in the face of a faulty
or erroneous substrate pool.
The human heritable anaemias are in part categorized by minor