@Magerette:
You asked for it. Here's how genes and memory works. I have deliberately simplified it a lot, omitting most details. Still it's a lot of maybe boring stuff to read. Don't say I didn't warn you.
1. Genes=Recipes for proteins.
Proteins are important substances in our cells, and they come in a lot of different shapes and with different functions. Each protein is made up of a sequence of amino acids, of which there are 20 normally used in human proteins. The hormone Insuline is among the smallest proteins, consisting of 51 amino acids, most proteins contain hundreds. For each protein, the exact sequence of amino acids is crucial, even a small deviation may completely disrupt its function. Thus it's important that each protein is made in the same way each time. And it's important that say Insulin is made exactly the same way also in our chikldren. That is the responsibility of DNA.
The DNA molecules which build our chromosomes are long strands contaiing sequences of nitrogen bases, two and two stands linked together. There are 4 different nitrogen bases: Adenine, Guanine, Cytosine and Thymine. We can say that these bases create a language consisting of 4 letters: A,C,G and T. The words in this language are all made of 3 letters (also called triplets), giving 64 possible words. These triplets represent amino acids, we can say that they are the names of the amino acids in DNA. An example: the triplet "TTG" is a DNA-ish for the amino acid "Phenylalanine". Each time a protein is made, a sequence of triplets is decoded, translated into the proper sequence of amino acids. (The cell uses special structures for this job, the so called ribosomes)
One particularly important group of proteins are the enzymes. Enzymes are catalyzers, that is, they speed up chemical reactions - in this case chemical reactions within the cells. By itself, these chemical reactions are slow. Only reactions catalyzed by enzymes run at practically useful speeds. Therefore, the set of enzymes within our cells determine the chemistry. And since enzymes are proteins, the recipes for each of them is stored in DNA. And this is how DNA determines the properties of our cells and by extension our bodies.
An example: Man is one of the (few) mammals that don't make Vitamin C, and therefore need it as a nutrient. Most mammals make their own. Why? Because they have the enzyme(s) for it. We don't. Why? Because our DNA doesn't containe the recipe.
2. Memory
There is much we don't know about how memory works, and even more that I don't know. Admittedly I am a bit rusty.
Nerve cells (also called neurons) are cells with a lot of branching extensions (filaments), which connect to other nerve cells. This is the anatomical basis for the two main functions of this type of cells:
- they're excitable, they react to stimuli by creating impulses (or signals) which then traverse the neuron and its extensionss
- they can transmit impulses from one cell to another
It is estimated that we have around 100 billion nerve cells in our brains with a total 100 trillion connections.
The connection between two nerve cells is called a synapse. The synapse is a one way coupling between the cells, that is, the impulse can transmit from one cell (called the presynaptic neuron, but we'll just call it Neuron1) to the other (Neuron2), and not the other way. When an impulse in Neuron1 reaches the synapse, a chemical substance called a neurotransmitter is released into the synapse. There are a lot of different transmittors: Acetylccholine, norepinephrine, dopamine, serotonine.... The transmitter molecules move across the synaptic space and attach to the surface of neuron2. By doing that they affect the excitability of that cell. Given enough stimuli a new impulse is created here, but usually more than one discharge of transmitter is needed.
Actually there are more than 2 neurons in a typical synapse. Some of these neurons will increase the excitability of neuron2, others may lower it. Together these neurons determine the overall excitability in the synapse. Another word for this is resistance. The higher the resistance, the more exciting discharges is needed to transmit a nerve signal.
And now comes the interesting part: The resistance may change over time, and this is how we learn new things, by lowering resistance in some synapses, and increasing resistance in others. The result is a narrowing and a change in the paths nerve signals take through the brain. Consider how an infant learns to catch a toy. Or a spider. Or tha daddy's glasses. Initially it's mainly random movements, occasional hits, but mostly misses. Over time the movements becomes more an more precise, as the brain finds the most efficient pathway of the nerve signals involved.
In other words, learning is implemented as a change of signal paths. The same principles apply when storing memories. (I can't say that's all there is, but changing connectivity and signal paths is an important part of it).
So, while gene expression and memory are both complicated, they're very different phenomena.
3. Genetic memory.
Genetic memory can mean several things:
In evolution it represent changes in genetic material during evolution of a species (not necessarily the entire set of changes). This history is part of the germ cells of the species, and is transferred from parent to the offspring.
Immunological memory. Antibodies are not created from one continous DNA segment. In stead different, smaller segments are combined in order to make these molecules. This allow for a huge variation of antibodies, and is also the basis for identifying and remembering for microbes you've been infected with. This type of memory is not transferred to the next generation, and the offspring is therefore not protected against infectious diseases from their parents. Admittedly newborn infants gets some protection from their mothers, because antibodies are transferred to the fetus through the placenta, and mother's milk also contain antibodies. But this is only temporary - when they're gone, the child has to develop it's own immunity.
The only way to transfer genetic information to the offspring is through the germ cells. Developing immunity affect how genes are expressed in the cells of the immune apparatus. But this does not change the germ cells, and therefore does not transfer to your children.
I've seen no example of memory of events you experience, facts, and languages you learn being stored in the genes. And even if it happened, I can see no way that changing genes in the brain could affect the genes of your germ cells. After all the cells giving rise to your germ cells are made before you were born, and in female babies, the eggs are actually halfway made when at birth.
So all in all - I don't believe these stories, that is if one tries to explain them by genetics.
4 One final question: How do children "inherit" the tastes, preferences and habits of their parents? Well, you may inherit physiological properties affecting for instance taste. I've read somewhere, don't bother checking it, that cats lack taste buds sensitive to sugars, and therefor is not attracted to sweets. Similar mechanisms may be involved in humans, I don't know. But in general I think most shared preferences are the result of you learning a lot from your parents during the 20 years or so you live with them. It's called social inheritance in Norway.
I did warn you.
