The design of life: part 3—an introduction to variation-inducing genetic elements
by Peter Borger
The inheritance of traits is determined by genes: long stretches of DNA that are
passed down from generation to generation. Usually, genes consist of a coding part
and a non-coding regulatory part. The coding part of the gene determines the functional
output, whereas the non-coding portion contains switches and units that determine
when, where and how much of the functional output should be generated. Point-mutations
in the coding part are predominantly neutral or slightly detrimental genetic noise
that accumulates in the genome, whereas point-mutations in the regulatory part of
DNA units can induce variation with respect to the amount of output. Previously,
in part 2, I argued that created kinds were frontloaded with baranomes: that is,
pluripotent genomes with an ability to induce variation from within. The output
of (morpho)genetic algorithms present in the baranome can readily be modulated by
variation-inducing genetic elements (VIGEs). VIGEs are frontloaded genetic elements
normally referred to as endogenous retroviruses, insertion sequences, LINEs, SINEs,
micro-satellites, transposons, insertion sequences, and the like. In the present
report, these transposable and repetitive DNA sequences are redefined as VIGEs,
which solves the RNA virus paradox. The (morpho)genetic algorithms were designed
in such way that VIGEs easily integrated into it and became a part of it, hence
making the program explicit.
Photo by Graham Manning, commons.wikimedia.org
The variation that Darwin saw in pigeons can be explained with the activation
or deactivation of existing genetic sequences for feather production in different
parts of the body. This gives no basis for asserting that pigeons could change into
something which is not a pigeon.
In order to fight off invading bugs and parasites, higher organisms have an elaborate
mechanism that induces variation in immunological defence systems. One particular
type of immune cells (B cells) produces defence proteins known as immunoglobulins.
Immunoglobulins are very sticky; they bind to intruders as biological tags and mark
them as ‘alien’. Other cells of the immune system then recognize the
intruder, and a destruction cascade is activated. To have a tag available for every
possible alien intruder, millions of B cells have their own highly specific gene
for immunoglobulin production. In the genome there is only limited storage space
for biological information, so how can there be millions of genes? Well, there aren’t.
Immunoglobulin genes are assembled from several pre-existing DNA sequences that
can be independently put together. The part of the immunoglobulin that does the
‘alien’ recognition contains several domains which are each highly variable.
Every single B cell forms a unique immunoglobulin gene by picking from several short
pre-existing DNA sequences. We also observe that later generations of immunoglobulins
are more specific than the earlier generations, in the sense that they bind more
tightly to invading microorganisms. Binding affinity to an invader is equivalent
to recognition of that invader. And the better the immune system is able to recognize
an intruder, the better it is able to clear it. The increased specificity is due
to somatic mutations deliberately introduced in the genes of the immunoglobulins.
A mechanism to rapidly induce mutations in immunoglobulin genes is present in the
B cell genome. This mechanism ensures that the recognition pattern specified by
the genes becomes increasingly specific for the intruder. This ability to recognize
and defeat all potential microorganisms is characteristic of the immune systems
of higher organisms, including humans. The genomes contain all the necessary biological
information required to induce variation from within. A flexible genome is required
to effectively ward off diseases and parasitic infections. B cells don’t wait
for mutations to happen; they generate the necessary mutations themselves.
Darwin revisited
Previously, in part 2,1
I argued that organisms are equipped with flexible, highly adaptable, pluripotent,
multipurpose genomes. Organisms are able to conquer the world through adaptive radiation
of baranomes. But how do baranomes unleash information? Do organisms have
to wait for selectable mutations to occur in order to rapidly invade and occupy
novel ecological niches? Or were the baranomes of created kinds equipped with mechanisms
to rapidly induce mutations, similar to the variation generated by B cells? Let’s
turn to Darwin’s The Origin of Species, where we will find some clues.
Darwin wrote quite extensively on variation, and in particular on the variation
of feather patterns in pigeons:
Box 1. Common names of some well-known variation-inducing genetic elements (VIGEs) in prokaryotes
(bacteria) and eukaryotes (yeast, plants, insects and mammals).
‘Some facts in regard to the colouring of pigeons well deserve consideration.
The rock-pigeon is of a slaty-blue, and has a white rump (the Indian sub-species,
C. intermedia of Strickland, having it bluish); the tail has a terminal
dark bar, with the bases of the outer feathers externally edged with white; the
wings have two black bars; some semi-domestic breeds and some apparently truly wild
breeds have, besides the two black bars, the wings chequered with black. These several
marks do not occur together in any other species of the whole family. Now, in every
one of the domestic breeds, taking thoroughly well-bred birds, all the above marks,
even to the white edging of the outer tail-feathers, sometimes concur perfectly
developed. Moreover, when two birds belonging to two distinct breeds are crossed,
neither of which is blue or has any of the above specified marks, the mongrel offspring
are very apt suddenly to acquire these characters; for instance, I crossed some
uniformly white fantails with some uniformly black barbs, and they produced mottled
brown and black birds; these I again crossed together, and one grandchild of the
pure white fantail and pure black barb was of as beautiful a blue colour, with the
white rump, double black wing-bar, and barred and white-edged tail-feathers, as
any wild rock pigeon! We can understand these facts, on the well-known principle
of reversion to the ancestral characters, if all the domestic breeds have descended
from the rock-pigeon.’2
Darwin argues—and correctly so—that all domestic pigeon breeds have
descended from the rock-pigeon. He even knew, as demonstrated above, how to breed
the rock-pigeon from several distinct pigeon races following a breeding pattern.
Darwin describes a breeding algorithm for pigeons, to obtain the ancestor
to all pigeons! But does he also describe an algorithm for breeding turkeys from
pigeons? No. Darwin doesn’t know such an algorithm. If he had found an algorithm
for breeding ducks or magpies from pigeon genomes, he would have had solid evidence
in favour of his proposal On The Origin of Species Through the Preservation of Favoured
Races. His breeding experiments led him to discover ‘the principle
of reversion to ancestral characters’, but contrary to common Darwinian wisdom,
it is also the falsifying observation to his proposal for the origin of
species. The observation that pigeons bring forth pigeons, and nothing
else but pigeons, is not exactly the evidence needed to argue for the common descent
of all birds. On the contrary! Darwin’s breeding experiments demonstrated
that a pigeon is a pigeon is a pigeon. Characteristics and traits within single
species of pigeons may vary tremendously, but he always started and ended with pigeons.
Breeding experiments have always shown, without exception, that novel and distinct
bird species do not arrive through artificial selection. Even Darwin argues that
there is no doubt that all varieties of ducks and rabbits have descended from the
common wild duck and rabbit.3
From the variation Darwin observed in wild and domesticated populations, it does
not follow that rabbits and ducks have some hypothetical common ancestor in a fuzzy
distant past. Darwin observed inborn, innate variation that already existed in the
genomes of the pigeons and it only had to be activated or expressed.
From the excerpt above, we may even get an impression of how it works. A genetic
algorithm for making feathers (a feather program) is part of the pigeon’s
genome and is present in every single cell. The feather program is present in billions
of pigeon cells, but it is NOT active in all those cells. Feathers are only formed
when the program is activated. The feather program is silent in cells where it should
normally not operate. Activation of the feather program in the wrong cells may often
be incompatible with life, but sometimes it may produce pigeons with (reversed)
feathers on the feet. The program may be derepressed or activated through a mechanism
that operates in the pigeon’s genome. Whether feathers appear on the feet
or on the head, and whether they appear normal or reversed is merely a matter of
activation and regulation of the feather program. But Darwin didn’t know about
silent genomic programs or how they could become active. He didn’t know about
gene regulation and molecular switches. Darwin did not know anything about genes
and genomes.
Analogous variation
The idea that Darwin had been working on for over two decades prior to the publication
of Origin, his idée fixe, was how organic change (i.e.
variation) present in populations might explain how novel species came into being.
Unchanging, stable species is not what Darwin had in mind. He pondered the riddles
of variation; he thought about laws and principles associated with the process of
variation and believed he could disclose them by the study of the formation of new
breeds. Drawing from what he knew about pigeon breeding and equine varieties, Darwin
describes some of his ideas about the ‘laws of variation’ in chapter
five of Origin:
‘Distinct species present analogous variations; and a variety of one species
often assumes some of the characters of an allied species, or reverts to some of
the characters of an early progenitor. These propositions will be most readily understood
by looking to our domestic races. The most distinct breeds of pigeons, in countries
most widely apart, present sub-varieties with reversed feathers on the head and
feathers on the feet, characters not possessed by the aboriginal rock-pigeon; these
then are analogous variations in two or more distinct races.’4
Darwin describes that the exact same traits can appear in distinct breeds of pigeons
and—importantly—these traits appeared independently in ‘countries
most widely apart’. If several breeds arrive with the same characteristics
independently, it is unlikely they do so because of chance. Rather, the pigeon genomes
may activate or derepress the same feather program independently. The effect is
that distinct breeds ‘in countries most widely apart’ acquire the same
characteristics. Over and over the same traits appear in separated populations of
organisms as the result of mutations ‘from within’. Animal breeders
like exuberant patterns and rarities; that is exactly what they are looking for
to select. Aberrant traits that are normally under stringent negative selection,
as might be the case for the pigeon’s reversed feathers, may readily become
visible as soon as the selective pressure is relieved; that is, when organisms are
reared and fed in the protective environment of captivity. Darwin called the phenomenon
of independent acquisition of the same traits analogous variation. It is
a common phenomenon well known to breeders, and Darwin easily found more examples
of analogous variation:
‘The frequent presence of fourteen or even sixteen tail-feathers in the pouter,
may be considered as a variation representing the normal structure of another race,
the fantail. I presume that no one will doubt that all such analogous variations
are due to the several races of the pigeon having inherited from a common parent
the same constitution and tendency to variation, when acted on by similar unknown
influences. In the vegetable kingdom we have a case of analogous variation, in the
enlarged stems, or roots as commonly called, of the Swedish turnip and Ruta baga
[sic] plants which several botanists rank as varieties produced by cultivation
from a common parent: if this be not so, the case will then be one of analogous
variation in two so-called distinct species; and to these a third may be added,
namely, the common turnip. According to the ordinary view of each species having
been independently created, we should have to attribute this similarity in the enlarged
stems of these three plants, not to the vera causa of community of descent,
and a consequent tendency to vary in a like manner, but to three separate yet closely
related acts of creation.’5
Analogous variation originates in the genome. Through rearrangement and/or transposition
of DNA elements, previously silent (cryptic) traits can be activated. The underlying
molecular mechanism can’t be merely random; if it were, then Darwin, and other
breeders, would not have observed the expression of the same traits independently
of each other. A more contemporary translation of analogous variation would be non-random
(or: non-stochastic) variation, and it implies some sort of mechanism.
Reversions
In the excerpt above, Darwin also describes what he calls reversions. By
this term he meant traits that are present in ancestors, then disappear in first
generation offspring, and then reappear in subsequent generations. Darwin acknowledged
that unknown laws of inheritance must exist, but still he talks about ‘the
proportion of blood’. Reversions are easily explained as traits present on
separate chromosomes, and the inheritance of such traits is best understood from
Gregor Mendel’s inheritance laws. Through Mendel’s discovery of the
genetic laws that underlie the inheritance of traits associated with chromosome
segregation (a hallmark of sexual reproduction), Mendel gave us a quantum theory
of inheritance. He found that traits are always inherited in well-defined and predictable
proportions, and do not just come and go. Darwin’s ‘reversions’
are traits that reappear in later generations due to the inheritance of the same
genes (alleles) from both parents.5 Darwin didn’t know about Mendel’s
laws of inheritance, neither did he know about how variation is generated in genomes.
What Darwin described in Origin, however, is that variation in offspring
is a rule of biology. What Darwin described in isolated species (whether domesticated
breeds or island-bound birds) was the result of a burst of abundant speciation resulting
from multipurpose genomes. Variant breeds of pigeons are the phenotypes of a rearranged
multipurpose pigeon genome. The Galápagos finches (with their distinct beaks
and body sizes) are the phenotypes of a rearranged multipurpose finch genome. Where
does the variation stem from in populations of Galápagos finches?
Darwin was well aware of the profound lack of knowledge on the origin of variation,
and did not exclude mechanisms or laws to drive biological variation:
‘I have hitherto sometimes spoken as if the variations so common and multiform
in organic beings under domestication, and in a lesser degree in those in a state
of nature had been due to chance. This, of course, is a wholly incorrect expression,
but it serves to acknowledge plainly our ignorance of the cause of each particular
variation.’6
Since Darwin’s days, almost all corners of the living cell have been explored
and our biological knowledge has expanded greatly. Through a vast library of data
generated by new research in biology, we now have the answers to many questions
of a biological nature that had puzzled Darwin. We may also have the answer to ‘the
cause of each particular variation’, although we may not be aware of it (yet).
That is not because it is hidden between billions of other books and hard to find.
No, it is because of the Darwinian paradigm. The mechanism(s) that drive biological
variations have been elucidated but are not yet recognized as such.
One of the findings of the new biology was that the DNA of most (if not all) organisms
contains jumping genetic elements. The mainstream opinion is that these elements
are the remnants of ancient invasions of RNA viruses. RNA viruses are a class of
viruses that use RNA molecule(s) for information storage. Some of them, such as
influenza and HIV, pose an increasing threat to human health. Are virus invasions
responsible for all the beautiful intricate complexity of organic beings? Is a virus
a creator? Most likely it is not. Otherwise why would we pump billions of research
dollars into research to fight off viruses? Could it be that mainstream science
is mistaken?
The RNA virus paradox
Here is one good reason for believing that mainstream science is indeed mistaken:
the RNA virus paradox. It has been proposed that these RNA viruses have a long evolutionary
history, appearing with, or perhaps before, the first cellular life forms.7 Molecular genetic analyses
have demonstrated that genomes, including those of humans and primates, are riddled
with ‘endogenous retroviruses’ (ERVs), which are currently explained
as the remnants of ancient RNA virus-invasions. RNA virus origin can be estimated
using homologous genes found in both ERVs and modern RNA virus families. By using
the best estimates for rates of evolutionary change (i.e. nucleotide substitution)
and assuming an approximate molecular clock,8,9 the families of RNA viruses
found today ‘could only have appeared very recently, probably not more than
about 50,000 years ago’.10
These data imply that present-day RNA viruses may have originated much more recently
than our own species. The implication of a recent origin of RNA viruses and the
presence of genomic ERVs poses an apparent paradox that has to be resolved. I will
argue, in order to resolve the paradox, we should abstain from the mainstream idea
that ERVs are remnants of ancient RNA virus invasions.
This intricate mechanism for transposition of ERVs seems to be irreducibly complex
(and thus a sign of intelligent design) since all ERVs and RNA viruses use the same
or similar genetic components.
Solving the RNA paradox can only be accomplished by asking questions. First, we
have to ask ourselves, What do scientists mean when they refer to genetic elements
as endogenous retroviruses (ERVs)? In addition, we have to ask, How do
ERVs behave, and what—if any—are their functions? ERVs have been extensively
studied in microorganisms, such as baker’s yeast (Saccharomices cerivisiae)
and the common gut bacterium Escherichia coli. Most of our knowledge on
the mechanisms of transposition of ERVs comes from those two organisms. In yeast,
the ERV known as Ty is flanked by long terminal repeats and specifies two
genes, gag and pol, which are similar to genes found in free operating
RNA viruses. This is the main argument why scientists believe RNA viruses and ERVs
are evolutionarily closely related. The long terminal repeats enable the ERV to
insert into the host’s DNA. The transposition and integration is a stringently
regulated process and seems to be target or site-specific.11,12
During the transpositions of an ERV, the host’s RNA polymerase II makes an
RNA template, which is polyadenylated to become messenger RNA. The gag
and pol mRNAs are translated and cleaved into several individual proteins.
The gag gene specifies a polyprotein that is cleaved into three proteins,
which form a capsid-like structure surrounding the ERV’s RNA. We may ask here:
why is a capsid involved? It should be noted that single stranded RNA molecules
are very sticky nucleotide polymers and the capsid may prevent the ERV from sticking
at wrong places. The capsid may also be required to direct the ERV to the right
spots in the genome. The pol polyprotein is cleaved into four enzymes:
protease, reverse transcriptase, RNase and integrase. Protease cleaves the polyproteins
into the individual proteins and then the RNA and proteins are packed into a retrovirus-like
particle. Reverse transcriptase forms a single-stranded DNA molecule from the ERV
RNA template, whereas RNase removes the RNA. The DNA is then circularized and the
complementary DNA strand is synthesized to create a double-stranded, circular copy
of the ERV, which is then integrated into a new site in the host’s genomic
DNA by integrase’s activity. This intricate mechanism for transposition of
ERVs seems to be irreducibly complex (and thus a sign of intelligent design) since
all ERVs and RNA viruses use the same or similar genetic components.
Variation-inducing genetic elements (VIGEs).
What can the function, if any, of ERVs be? If we follow the mainstream opinion,
ERVs integrated into the genomes a very long time ago as viral infections. Currently,
ERVs are not particularly helpful. They merely hop around in the genome as selfish
genetic elements that serve no function in particular. They are mainly upsetting
the genome. Long ago, however, RNA viruses are alleged to have significantly contributed
to evolution by helping to shape the genome.
It’s hard to imagine this story to be true, and not only because of the RNA
virus paradox. Modern viruses usually do not integrate into the DNA of the germ
line-cells; that is, the genes of an RNA virus don’t usually become a part
of the heritable material of the infected host. If we obey the uniformitarian principle,
we are allowed to argue: ‘What currently doesn’t happen didn’t
happen a long time ago, either’. To answer the question raised above, we must
start finding out more about some biological characteristics of a less complicated
jumping genetic element, the so-called insertion-sequence (IS) element.
IS elements are DNA transposons abundantly present in the genomes of bacteria. IS
elements share an important characteristic with ERVs: transposition. Genome shuffling
takes place in bacteria so frequently that we can hardly speak of a specific gene
order. The shuffling of pre-existing genetic elements may unleash cryptic information
instantly as the result of position effects. Shuffling seems to be an important
mechanism to generate variation. But what is the mechanism for genome shuffling?
The answer to this question comes unexpectedly from evolutionary experiments, in
which genetic diversity (‘evolutionary change’) was determined between
reproducing populations of E. coli. During the breeding experiment, which
ran for two decades, it was observed that the number and location of IS (‘insertion
sequence’) elements dramatically changed in evolving populations, whereas
point mutations were not abundant.13
After 10,000 generations of bacteria, the genomic changes were mostly due to duplication
and transposition of IS elements. A straightforward conclusion would thus be that
jumping genetic elements, such as the IS elements, were designed to deliberately
generate variation—variation that might be useful to the organism. In 2004,
Lenski, one of the co-authors of the studies, demonstrated that the IS elements
indeed generate fitness-increasing mutations.14
In E. coli bacteria IS elements activate cryptic—or silent—catabolic
operons: a set of genetic programs for food digestion. It has been reported that
IS element transposition overcomes reproductive stress situations by activating
cryptic operons, so that the organism can switch to another source of food. IS elements
do so in a regulated manner, transposing at a higher rate in starving cells than
in growing cells. In at least one case, IS elements activated a cryptic operon during
starvation only if the substrate for that operon was present in the environment.15
It is clear that in Lenski’s experiments, IS elements did not evolve over
night. Rather, the IS elements reside in the genome of the original strain. During
the two decades of breeding, the IS elements duplicated and jumped from location
to location. There was ample opportunity to shuffle genes and regulatory sequences,
and plenty of time for the IS elements to integrate into genes or to simply redirect
regulatory patterns of gene expression. Microorganisms may thus induce variation
simply through shuffling the order of genes and put old genes in new contexts: variation
through position effects that can be inherited and propagated in time. It’s
hardly an exaggeration to state that jumping genetic elements specified by the bacterium’s
genome generated the new phenotypes.
Transposition of IS elements is mostly characterized by local hopping, meaning that
novel insertions are usually in the proximity of the previous insertion and may
be a more-or-less random phenomenon; the site of integration isn’t sequence
dependent. Bacteria have a restricted set of genes and they divide almost indefinitely.
Therefore, sequence-dependent insertion and stringent regulation of transposition
may not be required for IS-induced reshuffling of bacterial genomes; in a population
of billions of microorganisms all possible chromosomal rearrangements may occur
due to stochastic processes. In ‘higher’ organisms the order of genes
in the chromosomes is more important, but there is no reason to exclude jumping
genetic elements as a factor affecting the expression of genetic programs through
position effects. Transposable elements may therefore be a class of variation-inducing
genetic elements (VIGEs) in ‘higher’ organisms. Indeed, ERVs, LINEs
and SINEs resemble IS elements in bacteria in that they are able to transpose. In
fact, these elements may be responsible for a large part of the variability observed
in higher organisms and may even be responsible for adaptive phenotypes. The genomic
transposition of VIGEs is not just a random process. As observed for Ty
elements in yeast, integration of all VIGEs may originally have been designed as
site or sequence specific. It should be noted that VIGEs might qualify as redundant
genetic elements, of which the control over translocation may have deteriorated
over time.
VIGEs in humans
Mobile genetic elements make up a considerable part of the eukaryotic genome and
have the ability to integrate into the genome at a new site within their cell of
origin. Mobile genetic elements of several classes make up more than one third of
the human genome.
Human endogenous retroviruses (ERVs) are, as with yeast ERVs, first transcribed
into RNA molecules as if they were genuine coding genes. Each RNA is then transformed
into a double stranded RNA-DNA hybrid through the action of reverse transcriptase,
an enzyme specified by the retrotransposon itself. The hybrid molecule is then inserted
back into the genome at an entirely different location. The result of this copy-paste
mechanism is two identical copies at different locations in the genome. More than
300,000 sequences that classify as ERVs have been found in the human genome, which
is about 8% of the entire human DNA.16
Figure 1. Variation-inducing genetic elements (VIGEs) are found throughout all biological
domains, ranging from bacteria to mammals. In yeast, insects and mammals we observe
similar designs. (Homologous sequences are indicated by the same colour).
Long terminal repeats retrotransposons (LTR retrotransposons)
are transcribed into RNA and then reverse transcribed into a RNA-DNA hybrid and
reinserted into the genome. LTRs and retroviruses are very similar in structure.
Both contain gag and pol genes
(figure 1), which encode a viral particle coat (GAG), reverse transcriptase (RT),
ribonuclease H (RH) and integrase (IN). These genes provide proteins for the conversion
of RNA into complementary DNA and facilitate insertion into the genome. Examples
of LTR retrotransposons are human endogenous retroviruses (HERVs). Unlike RNA retroviruses,
LTR retrotransposons lack envelope proteins that facilitate movements between cells.
Non-LTR retrotransposons, such as long interspersed elements (LINEs), are
long stretches (4,000–6,000 nucleotides) of reverse transcribed RNA molecules.
LINEs have two open reading frames: one encoding an endonuclease and reverse transcriptase,
the other a nucleic acid binding protein (figure 1). There are approximately 900,000
LINEs in the human genome, i.e. about 21% of the entire human DNA. LINEs are found
in the human genome in very high copy numbers (up to 250,000).17
Short interspersed elements (SINEs) constitute another class of VIGEs that
may use an RNA intermediate for transposition. SINEs do not specify their own reverse
transcriptase and therefore they are retroposons by definition. They may
be mobilized for transposition by using the enzymatic activity of LINEs. About one
million SINEs make up another 11% of the human genome. They are found in all higher
organisms, including plants, insects and mammals. The most common SINEs in humans
are Alu elements. Alu elements are usually around 300 nucleotides long,
and are made up of repeating units of only three nucleotides. Some Alu elements
secondarily acquired the genes necessary to hop around in the genome, probably though
recombination with LINEs. Others simply duplicate or delete by means of unequal
crossovers during cell divisions. More than one million copies of Alu elements,
often interspersed with each other, are found in the human genome, mostly in the
non-coding sections. Many Alu-like elements, however, have been found in the introns
of genes; others have been observed between genes in the part responsible for gene
regulation and still others are located within the coding part of genes. In this
way SINEs affect the expression of genes and induce variation. Alu elements are
often mediators of unequal homologous recombinations and duplications.18
Figure 2. Schematic view of the central role VIGEs may play to generate variation, adaptations
and speciation events. Lower part: VIGEs may directly modulate the output of (morpho)genetic
algorithms due to position effects. Upper part: VIGEs that are located on different
chromosomes may be the result of speciation events, because their homologous sequences
facilitate chromosomal translocations and other major karyotype rearrangements.
Repetitive triplet sequences (RTSs) present in the coding regions of proteins
are a class of VIGEs that cannot actively transpose. RTSs are usually found as an
intrinsic part of the coding region of proteins. For instance, RTSs can be formed
by a tract of glycine (GGC), proline (CCG), or alanine (GCC). Usually RTSs form
a loop in the messenger
(m)RNA that provides a docking site for chaperone molecules or proteins involved
in the mRNA translation. RTSs may increase or decrease in length through slippery
DNA polymerases during DNA replication.
Conclusions and outlook
Now that we have redefined ERVs as a specific class of VIGEs, which were present
in the genomes from the day they were created, it is not difficult to see how RNA
viruses came into being. RNA viruses have emerged from VIGEs. ERVs, LINEs and SINEs
are the genetic ancestors of RNA viruses. Darwinists are wrong in promoting ERVs
as remnants of invasions of RNA viruses; it is the other way around. In my opinion,
this view is supported by several recent observations. RNA viruses contain functional
genetic elements that help them to reproduce like a molecular parasite. Usually,
an RNA virus contains only a handful of genes. Human Immunodeficiency virus (HIV),
the agent that causes AIDS, contains only eight or nine genes. Where did these genes
come from? An RNA world? From space? The most parsimonious answer is: the RNA viruses
got their genes from their hosts.
These observations make it plausible that all RNA viruses have their origin in the
genomes of living cells through recombination of host’s DNA elements
The Rous arcoma virus (RSV), which has the ability to cause tumours, has only 4
genes: gag, pol, env and src. In addition, the
virus is flanked by a set of repeat sequences that facilitate integration and promote
replication. Gag, pol and env are genes commonly present
in ERVs. The src gene of RSV is a modified host-derived src gene
that normally functions as a tyrosine kinase—a molecular regulator that can
be switched on and off in order to control cell proliferation. In the virus, the
regulator has been reduced to an on-switch only that induces uncontrolled cell proliferation.
The src gene is not necessary for the survival of RSV, and RSV particles
can be isolated that have only the gag, pol and env genes.
These have perfectly normal life cycles, but do not cause tumours in their host.
It is clear the virus picked up the src gene from the host. Why wouldn’t
the whole vector be derived from the host? VIGEs may easily pick up genes or parts
thereof as the result of an accidental polymerase II read-through. This will increase
the genetic content of the VIGE because the gene located next to the VIGE will also
be incorporated. An improper excision of VIGEs may also include extra genetic information.
Imagine for instance HERV-K, a well-known human-specific endogenous retrovirus,
transposing itself to a location in the genome where it sits next to the src
gene. If in the next round of transposition a part of the src gene was
accidentally added to the genes of HERV-K, it has already transformed into a fully
formed RSV (see figure 3). It can be demonstrated that most RNA viruses are built
of genetic information directly related to that of their hosts.
Figure 3. RNA viruses originate from VIGEs through the uptake of
host genes. In the controlled and regulated context of the host DNA, genes and VIGEs
are harmless. A combination of a few genes integrated in VIGEs may start an uncontrolled
replication of VIGEs. In this way, VIGEs may take up genes that serve to form the
virus envelope (to wrap up the RNA molecule derived from the VIGE) and genes that
enable them to leave and re-enter host cells. Once VIGEs become full-blown shuttle
vectors between hosts, they act as virulent, devastating and uncontrolled replicators.
Hence, harmless VIGEs may degenerated into molecular parasites in a similar way
normally harmless cells turn into tumors once they lose the power to control cell
replication. VIGEs are on the basis of RNA viruses, not the other way around. The
scheme outlined here shows how the Rous sarcoma virus (RSV) may have formed from
a VIGE that integrated the env gene and part of the src gene (a
proto-oncogene: for details see text).
The outer membranes of influenza viruses, for instance, are built of hemagglutinin
and neuraminidase molecules. Neuraminidase is a protein that can also be found in
the genomes of higher ‘host’ organisms, where it serves the function
to modify glycopeptides and oligosaccharides. In humans, neuraminidase deficiency
leads to neurodegenerative lysosomal storage disorders: sialidosis and galactosialidosis.19 Even so-called orphan genes,
genes that are only found in viruses, can usually be found in the host genomes.
Where? In VIGEs!
To become a shuttle-vector between organisms, all that is required is to have the
right tools to penetrate and evade the defenses of the host cell. HIV, for instance,
acquired part of the gene of the host’s defence system (the gp120 core) that
binds to the human beta-chemokine receptor CCR5.20
These observations make it plausible that all RNA viruses have their origin in the
genomes of living cells through recombination of host’s DNA elements (genes,
promoters, enhancers). Every now and then such an ‘unfortunate’ recombination
produces a molecular replicator: it is the birth of a new virus. Once the virus
escapes the genome and acquires a way to re-enter cells, it has become a fully formed
infectious agent. It has long been known that bacteria use genes acquired from bacteriophages—i.e.
bacterial viruses that insert their DNA temporarily or even permanently into the
genome of their host—to gain reproductive advantage in a particular environment.
Indeed, work reaching back decades has shown that prophage (the integrated virus)
genes are responsible for producing the primary toxins associated with diseases
such as diphtheria, scarlet fever, food poisoning, botulism and cholera. Diseases
are secondary entropy-facilitated phenomena. Virologists usually explain the evolution
of viruses as recombination: that is, a mixing of pre-existing viruses, a reshuffling
and recombination of genes.21
In bacteria, viruses may therefore be recombined from plasmids carrying survival
genes and/or transposable genetic elements, such as IS elements.
Discussion
Where did all the big, small and intermediate noses come from? Why are people tall,
short, fat or slim? What makes morphogenetic programs explicit? The answer may be
VIGEs. It may turn out that the created kinds were designed with baranomes that
had an ability to induce variation from within. This radical view implies that the
baranome of man may have been designed to contain only one morphogenetic algorithm
for making a nose. But the program was implicit. The program was designed in such
way that a VIGE easily integrated into it, becoming a part of it, hence making the
program explicit. Most inheritable variation we observe within the human population
may be due to VIGEs—Elements that affect morphogenetic and other programs
of baranomes. It should be noted that a huge part of the genomic sequences are ‘redundant’
adaptors, spacers, duplicators, etc., which can be removed from the genome without
major affects on reproductive success (fitness). In bacteria, VIGEs have been coined
IS elements; in plants they are known as transposons; and in animals, they are called
ERVs, LINEs, SINEs, and microsatellites. What these elements are particularly good
at is inducing genomic variation. It is the copy number of VIGEs and their position
in the genome that determine gene expression and the phenotype of the organism.
Therefore, these transposable and repetitive elements should be renamed after their
function: variation-inducing genetic elements. VIGEs explain the variations
Darwin referred to as ‘due to chance’.
I will address the details of a few specific classes of VIGEs and argue why modern
genomes are literally riddled with VIGEs in a future article. With the realization
that RNA viruses have emerged from VIGEs the RNA paradox is solved. For many mainstream
scientists this solution will be bothersome because VIGEs were frontloaded elements
of the baranomes of created kinds and that implies a young age for their common
ancestor and that all life is of recent origin.
Further reading
References
- Borger, P., Evidence of the design of life: part
2–Baranomes, J. Creation 22(3):68–76, 2008.
Return to text.
- Darwin, C., The Origin of Species by means of Natural
Selection or
The Preservation of Favoured Races in the Struggle for Life, first published
by John Murray, 1859. References from Penguin Classics, pp. 85–86, 1985. Return to text.
- Darwin, ref. 2, p. 80. Return to text.
- Darwin, ref. 2, p. 195. Return to text.
- Many recessive traits that come and go in offspring and inherit
in a Mendelian fashion can be understood as inactivated redundant genes.
Return to text.
- Darwin, ref. 2, p. 173. Return to text.
- Strauss, E.G., Strauss, J.H. and Levine A.J., Virus evolution;
in: Fields, B.N., Knipe, D.M. and Howley, P.M. (Eds.), Fundamental virology,
3rd ed., Raven Press, New York, pp. 141–159, 1996. Return to
text.
- Jenkins, G.M. et al., Rates of molecular
evolution in RNA viruses:
a quantitative phylogenetic analysis, J. Mol. Evol. 54:152–161,
2002. Return to text.
- Sala, M. and Wain-Hobson, S., Are RNA viruses adapting or
merely changing? J. Mol. Evol. 51:12–20, 2000. Return to text.
- Holmes E.C., Molecular clocks and the puzzle of RNA virus
origins, J. Virology 77:3893–3897, 2003.
Return to text.
- Barabaugh, P.J., Post-transcriptional regulation of transposition
by Ty retrotransposons of Saccharomyces cerevisia, J. Biol. Chem.
270:10361–10264, 1995. Return to text.
- Wilke, C.M., Maimer, E. and Adams, J., The population biology
and evolutionary significance of Ty elements in Saccharomyces cerevisiae,
J. Genetics 86:155–173, 1992. Return
to text.
- Papadopoulos, D. et al., Genomic evolution
during a 10,000-
generation experiment with bacteria, Proc. Natl Acad. Sci. USA, 96:
3807–3812, 1999. Return to text.
- Schneider, D. and Lenski, R.E., Dynamics of insertion sequence
elements during experimental evolution of bacteria, Res. Microbiol.
155:319–327, 2004. Return to text.
- Hall, B.G., Transposable elements as activators of cryptic
genes in E. coli, Genetica 107:181–187,
1999. Return to text.
- Belshaw, R. et al., Long-term reinfection
of the human genome
by endogenous retroviruses, Proc. Natl Acad. Sci. USA 101(14):4894–4899,
2004. Return to text.
- Pierce, B.A., Genetics: A conceptual approach, W.H.
Freeman, New York, p. 311, 2005. Return to text.
- Lonnig, W.E. and Saedler, H., Chromosome rearrangements and
transposable elements, Annu. Rev. Genet. 36:389–410,
2002. Return to text.
- Neuraminidase deficiency, National Centre for Biotechnology
Information, Online Mendelian Inheritance in Men, <www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=256550>,
5 December 2008. Return to text.
- Nolan, K.M., Jordan, A.P. and Hoxie, J.A., Effects of partial
deletions within the HIV-1 V3 Loop on coreceptor tropism and sensitivity to entry
inhibitors, J. Virol. 82: 664–673, 2008.
Return to text.
- Hamilton G., Virology: the genes weavers, Nature
441:683–685, 2006. Return to text.
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