A Quick FAQ About
Epigenetics
- A: The early development
from zygote (egg cell in parthenogenetic organisms)
to the phylotypic stage is determined not by
zygotic genes but by the epigenetic information
provided by parent(s) to gametes (egg cell and
sperm cells) in the form of parental cytoplasmic
factors in a strictly determined spatio-temporal
order. That information regulates the spatiotemporal
expression pattern of zygotic genes up to the
phylotypic stage.
- A: There is evidence
suggesting that this epigenetic information
flows down from the CNS to gametes via specific
signal cascades by utilizing and modifying the
structure of microtubules and cytoskeleton of
the gamete (see
chapter
4 of Epigenetic Principles of Evolution).
- A: Adequate empirical evidence on
post-phylotypic development shows that the development
of various organs in metazoans depends on CNS
signals or signal cascades originating in the
embryonic CNS, the brain or the spinal cord
(see
chapter
6 of Epigenetic Principles of Evolution),
clearly suggesting that the embryonic CNS is
the source of the epigenetic information determining
organogenesis and individual development in
general.
- A:
Solid evidence shows that developmental changes
that lead to the appearance of qualitatively
new characters within the lifetime of individuals,
i.e. without changes in genes, result from activation
of signal cascades that start with brain signals,
implying that the brain is the source of the
epigenetic information determining the new characters
(see chapter 11 of
Epigenetic Principles of Evolution
 ).
- A:
Based on experimental evidence from the
studied cases of TDP, it may be concluded that
the epigenetic information for this epigenetic
inheritance originates in the CNS. That evidence
has made possible reconstruction of a generalized
mechanism of induction of the TDP which looks
as follows: the specific environmental stimulus
is received by sensory neurons, and converted
into electric spike trains that are processed
in specific neural circuits. The processing
of the stimulus, which is a computational non-genetic
process, generates information in the form of
a chemical output (neurotransmitter, neuromodulator,
etc.) that is released on specific secretory
neurons, which, in turn secrete a neurohormone
that starts the signal cascade for deposition
in the gamete of a parental factor that determines
the development of the new phenotypic character
in the offspring (see
chapter 12 of Epigenetic
Principles of Evolution).
- A:
No (if evolutionary change implies the appearance
in successive generations of a new character
that the parent(s) lacked).
- A: In
a few cases it has experimentally been
determined that the information for
activating signal cascades inducing
inherited changes is generated (not stored)
in the CNS by processing particular
environmental stimuli in neural circuits
whose chemical output (neurotransmitter or neuromodulator) activates the signal cascade
that enables deposition of a specific factor
in the egg cytoplasm (see
chapter 12 of
Epigenetic Principles of Evolution).
- A: All the evolutionary changes described in
chapter 14 of
Epigenetic Principles of Evolution (pp. 379-500) involve no changes in genes and
are epigenetically determined.
- A: Epigenetic mechanisms
determining evolutionary changes described in
chapter 14 of Epigenetic Principles of Evolutioninvolve changes in the patterns of expression of genes
(but not changes in genes themselves) involved in signal cascades
determining development of specific characters. The information necessary
for the activation and changes in the expression patterns of genes in the
signal cascade originates in the CNS [this seem to have been the case in the
evolution of the body size in laboratory strains of Manduca sexta,
evolution of wings in insects, evolution of caste polymorphism in some
insect species, evolution of horns in beetles, evolution of dentition in
vertebrates, evolution of plumage dichromatism in birds, evolution of
alternation of sexual and asexual generations in crustaceans, evolution of
flight in insects, evolution (evolutionary acquisition and loss) of vocal
learning in birds, evolution of migration light-dependent magnetic
orientation etc.
- A: While allopatric speciation, formation of new species may result
from geographic isolation of two groups of an original population, speciation occurring
in sympatry may be a cause and a mechanism of evolutionary change and phenotypic diversification.
- A: Metazoans have evolved neurocognitive mechanisms that make assortative mating
possible in sympatry.
- A: It is a neuro-cognitive mechanism that enables a group of individuals
of a population to recognize and preferably mate only with individuals of the opposite sex in sympatry displaying a
particular sensory (visual, auditory, olfactory, electric behavioral) character. This implies the occurrence of a change
in a sensory signal of the sender (most commonly males) and a corresponding change in the receiver’s (commonly females)
mate preference for that signal, but involves no changes in genes of the sender or the receiver.
- A: This conventional guess is not true. All the known changes in sender’s signals (visual, olfactory,
acoustic, electric, behavioral) involve neither changes in the existing genes (gene mutations) nor
the evolution of new genes
but only changes in the expression of existing functionally unchanged genes. As for the corresponding changes in the receiver’s
mate preferences, they result from changes in properties of respective neural circuits, which also are not related to any
changes in genes.
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