Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Instinct encoded in DNA?

Tags:
  1. May 3, 2012 #1
    I was wondering how instinct or other forms of 'memory' are encoded in DNA. It seems there is a reservoir of knowledge that is stored in some way. Is this currently explained in genetics?
     
  2. jcsd
  3. May 3, 2012 #2

    Pythagorean

    User Avatar
    Gold Member

    I think instinct and memory are more emergent properties that come from the interactions between genetics and environment. In the most general sense, a memory is a representation of interactions with the environment stored internally in a system and DNA can do that in a more reduced way, but the specific kind of memory you're thinking of emerges from cellular networks which DNA underlies.

    DNA doesn't know about what's going on with memories and stimulus. This might possibly answer the question in your other thread about evolution and perception. On the one hand, the system has to have lots of internal degrees of freedom to sufficiently model external representations. But on the other hand, it has to keep the core code (DNA) safe, so it tends to be very stable.

    But the DNA is a like a multiple choice set of answers. Protein networks in cells turn off and on genes as they're needed, and some genes may never need to be expressed for a particular organism. This is kind of the arsenal of DNA the cells have, but for the most part it is fixed. It doesn't receive any information bout what the organism is perceiving. That is the central dogma of biology.

    So apparently, it's only by chance that this arrangement of molecules in this environment leads to this behavior that is so beneficial.

    DNA, in its own right, has been compared to associative memory:
    http://staff.elka.pw.edu.pl/~RNOWAK2/publ/assocmem.pdf [Broken]

    But this is a different kind of memory. You might call it uber-long-term memory.
     
    Last edited by a moderator: May 6, 2017
  4. May 4, 2012 #3
    Good response, thank you.

    I see that this thread is related to my other thread on perception. To ask the question differently...I observe directly that behavior is passed on, simply watching squirrels demonstrates this. I then ask how is behavior and capacity (tremendous and immediate climbing skill by young squirrels) passed on. Lets leave asside "soft inheritance" for now. What is the nature of this encoding? How is this information 'held' in the DNA? I have no idea about the information capacity of DNA (I would like to know), but it seems that particular structures in the brain get communicated through DNA. Does DNA have sufficient information storing capacity?
     
  5. May 4, 2012 #4

    Pythagorean

    User Avatar
    Gold Member

    It's a code with an alphabet of four letters. Little proteins come along and take a chunk of the code and make a simple copy of it called RNA, leaving the DNA safe. In a string of different combinations of these four letters in the RNA, every set of three letters is considered a "codon" and these codons are "read" by a ribosome that creates an "amino acid". So the ribosome will make several amino acids in a row and they might fold up or change geometry a bit into a functional shape and we call this a "protein" and the proteins are little molecular machines that do magnificent things at the molecular level.

    http://en.wikipedia.org/wiki/Genetic_code
     
  6. Nov 9, 2013 #5
    instinct in embryonic brain

    DNA has all the alfabets of life, and it also has the alfabets for instinct "memory knowledge".
    Did you want to know how this memory looks like in embryonic brain and how it is made with the DNA?
    I would like to know it too. John
     
  7. Nov 10, 2013 #6

    Ygggdrasil

    User Avatar
    Science Advisor

    In many animals, basic instincts and behaviors are encoded in the organism's DNA. The DNA provides instructions for the animal to build specific neural circuits to perform certain behaviors in response to certain stimuli. For example, flies have an escape response triggered by certain stimuli, such as a shadow passing over them. Researchers have identified a specific nerve cell in the fly that controls this response and this nerve cell is the same in all flies of the same species. Artificial stimulation of this nerve cell triggers the escape response. The nematode worm, C. elegans is probably the animal where the neural circuitry for many innate behaviors, as well as the genetic elements controlling the development of the circuitry, is best understood (for example, see http://www.ncbi.nlm.nih.gov/books/NBK20005/).

    In humans and other higher mammals, however, the situation is very different. Humans are born with very few innate behaviors and instincts. For example, whereas many animals (insects, fish, reptiles, amphibians, etc.) are fully capable of walking, feeding themselves and even surviving independently after birth, human babies can do practically nothing after birth and cannot survive without a caretaker. The difference here is that the DNA of humans does not specify a wiring diagram for the brain. Rather this wiring diagram is formed in response to the experiences of the individual. For example, if you were to take a newly born baby and cover its eyes for its entire early childhood, the child's neural circuitry for interpreting visual stimuli would not develop and the child would be blind despite the fact that the child's eyes work perfectly well. Another consequence of this strategy is that everyone will develop different neural circuits to perform the same functions. For example, whereas the same nerve cell will trigger the same escape response in all flies, activating a specific nerve in humans would likely trigger very different responses in different individuals.

    While this wiring-on-the-fly strategy has many disadvantages in the younger phases of life (babies and children are very much dependent on others for survival), this plasticity of the brain associated with the wiring strategy gives humans an unparalleled ability to learn. This neural plasticity is likely one reason why humans can learn complex tasks like reading and writing while other organisms cannot.
     
  8. Nov 10, 2013 #7

    Pythagorean

    User Avatar
    Gold Member

    There was an interesting distinction made in a study on neuronal regulatory function between innate behavior and learned behavior in barn owls:

    ---

    This is an interesting phenomena. It can actually be suppressed by suppressing the signaling of the neurons involved. If you don't suppress their activity, they try to make correlations on what are essentially noise signals in the system and "hard wire" the system by misinterpreting the meaningfulness of those signals.

    The hardwiring function is also discussed in the Caroni et al paper; it comes from these molecular casings that coat the neurons called perineuronal nets. This prevents further activity-induced plasticity from taking place.

    Caroni P, Donato F, Muller D. (2012) Structural plasticity upon learning: regulation and functions. Nat Rev Neurosci. 2012 Jun 20;13(7):478-90. doi: 10.1038/nrn3258.
    http://www.ncbi.nlm.nih.gov/pubmed/22714019
     
  9. Nov 11, 2013 #8
    Hi Pythagorean: I was actually wondering about dualistic nature of brain. One part has "instinct knowledge" already part of the structure from our ancestors ( ROM type, that you are not able to change). how has it been formed? The other is brain that you can "program", that means, put in and take out information.
     
  10. Nov 11, 2013 #9

    Pythagorean

    User Avatar
    Gold Member

    I wouldn't consider instinct knowledge as coming from our ancestors... at least not in the sense that they discovered something and it stuck in their DNA or whatnot.

    It's more just that particular sets of instinctual traits happened to emerge form reduced DNA instructions and those traits were successful in producing offspring who could successfully produce more offspring. It's like following a set of instructions "go left", "go right", "go straight" but the instructions weren't written with any goal in mind... they just happened to lead to a place that enabled recurrence.

    The instruction sets that were successful are what we have today, but they're not memories. They are the result of successful mutations. Babies are born with a whole set of reflexes that essentially enables their survival. When they first leave the womb and air hits their face, they begin to breathe. This isn't because a baby in the past discovered breathing at birth, it's because of mutation... and any organism that didn't have this mutation died and couldn't reproduce.
     
  11. Nov 11, 2013 #10

    Q_Goest

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Hi Ygggdrasil. Are you saying that if an animal's eyes were covered in the same way the child's eyes were, the animal would still be able to see?
     
  12. Nov 11, 2013 #11

    Ygggdrasil

    User Avatar
    Science Advisor

    It depends on the animal. The "wiring-on-the-fly" strategy applies mostly to mammals (and indeed, the dark-rearing experiments were done in mammals like mice and cats and not humans), so most mammals will behave similarly to us. I would suspect, however, that dark rearing of simpler animals like insects might not interfere with the proper development of the neural circuits to process visual information.
     
  13. Nov 12, 2013 #12

    Q_Goest

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Interesting! thank you.
     
  14. Nov 12, 2013 #13
    Aren't human babies born prematurely, their (our) brains are still developing years after birth, I believe walking (Inuit babies are wrapped tight long time after birth) and talking are human instincts, they are complicated motor movements that has nothing to do with reflexes (breathing).
    Anyways, past life memory can be something that can or can not be explained with DNA?
    Strange, my cat was born blind as all cats are but cat's vision is weird, maybe because of that?
    Talking about cats, behavior of my cat and African lions are similar. There hasn't been meeting with cats has there?
     
  15. Nov 12, 2013 #14

    Pythagorean

    User Avatar
    Gold Member

    Prematurely is defined with respect to the organism. So as a matter of technicality, no, most human babies aren't.

    But yes, ignoring semantics, our enormous heads mean that mothers must give birth to their children sooner than other mammals do and a lot of brain development takes place outside of the womb. Humans are quite useless when they're born: they can't even support their own heads. Many other mammals are born practically knowing how to walk.
     
  16. Nov 12, 2013 #15

    Evo

    User Avatar

    Staff: Mentor

    Sorry, this is a science forum, please read the rules. We don't allow mysticism.
     
  17. Nov 24, 2013 #16
    Hi Pythagorean. Some of the early separated twin studies are interesting. One twin has been doing the very same things in his/her life as the other one.
    What happens must be in the part of DNA that develops in to brain. If you just take the average of the studied twins there is no correlation but that is not what we are interested in. John
     
  18. Nov 24, 2013 #17

    Pythagorean

    User Avatar
    Gold Member

    Yes, twin studies are an interesting way to tease apart genetics from environment, but I don't understand what you're asking or saying.

    You also have to remember that their are influences in the womb too (for example, monozygotic twins can be monoamniotic and monochorionic and these can lead to different nutrient intake rates for each which can have effects on brain development).
     
  19. Feb 16, 2017 #18
    I have read a couple of threads I found via search, but none actually explain simply for me how it is that instinct is first formed and then inherited. I understand that instincts are presumably selected for, but it's not apparent to me how that happens. I just don't know enough about evolution.

    Given that species change occurs through changes to DNA in germ cells being passed on through reproduction, does it follow that the same process underpins instinct formation? That is, some genetic change to germ cell DNA confers a new "hard-wired" behaviour that may or may not be beneficial. If beneficial it is selected for and over time complex behaviours evolve that are coded for within DNA. In which case at an abstract level evolution of instinctual behaviour conforms to the same paradigm as evolution of physical characteristics and given that physical characteristics at the neural level are what generates instinctual behaviours, we are really looking at the same thing in both cases? In other words is the evolution of physical characteristics via reproduction and selection all there is?
     
  20. Feb 17, 2017 #19

    Pythagorean

    User Avatar
    Gold Member

    Yeah, it's just like anything else that's formed. Some random mutation made a small difference statistically in the population, providing advantage to survival or reproduction. In this case, the random mutation could be in the genes that code for neural organization or individual neuron properties (including 2nd messenger signaling). The random mutation may lead to a slightly different wiring that biases towards a certain input/output relationship (e.g. a muscle reflex that triggers when skin sensors are activated) that reduces infant mortality rates. As time goes by and more mutations occur, eventually another one in some other random aspect of cell organization happens to contribute to that reflex, too, and it becomes even more selected for... one, two, skip a few million years, and you have the palmar grasp reflex.

    "is the evolution of physical characteristics via reproduction and selection all there is?"

    Too strong of a statement to say it's "all there is". Does it all have a physical correlate? Yes. But it doesn't necissarily have to be limited to DNA-based inheritance if epigenetics carries the information through methylation. In which case, methylation is the physical correlate.
     
  21. Feb 17, 2017 #20

    BillTre

    User Avatar
    Science Advisor

    Yes. Instinctive behavior will (to the extent that it is genetically determined) will be underlain by the same selection process as everything else.
    The genes involved will direct developmental processes (perhaps with some environmental input, such as visual stimuli to promote normal visual system development).
    This results in a nervous system whose functioning underlies behavior, including instinctual behavior.

    The genetic component of behavior control can be pretty exact.
    bendless: is a fruitfly mutation that, among other things, blocks an escape instinct.
    The reflex occurs when the fly sees a increasing area of dark in its visual field (potential approaching predator). This triggers a giant escape fiber (axon) to fire, which triggers leg motoneurons to fire, which causes the fly to jump off the substrate, which in turn turns on (lack of contact between feet and substrate) the the flies flight system (fly flies away).
    The bendless mutation deletes a particular synapse between the giant fiber and the leg motoneurons, blocking that step in the behavior and therefore to escape response.

    bendless was found in a genetic screen for mutations in which this behavior (which is normally strong) does not occur. Flies in which the behavior occurred (and therefore did not have mutations affecting this behavior) ended up dead in the test apparatus (fell into a pot of oil). The survivors did not jump, did not die, and carried mutations. Thousands to millions of flies were tested in this way, which amounts to a selection (artificial not natural). Geneticists like selection screens because most of the initial work to find the mutants is done by the selection process making screening the huge numbers of flies feasible.

    Mutations in several different genes were found in this screen indicating there are many ways (genetically) to modify this particular behavior.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Instinct encoded in DNA?
Loading...