Genes and genetics, a bit of history

Everybody talks about genes these days, mainly keeping this old and crazy idea that genes can keep  hidden secrets, with no possibility of changes, but recent researches show how much we still have to learn from them, but first, a little bit of history...

 

Since far-off times humans have realized that many of their bodily and psychological characteristics as well as their diseases, concentrated in some families and that these traits tend to be inherited from one generation to another. Thus they figured out that genetics plays an important role in not only cognitive but human development in general. 

 

Learning, is not exempt from this influence, at one way or another, some skills are scheduled since before birth, but they will be modeled with  culture and environment influences that allows these primary skills. 

It's not the case beginning a debate on whether genetics has more weight than the environment or Vice Versa,  what this post wants to highlight is the existence of critical periods that can be, if necessary, be extended, thanks to brain plasticity and depend on learning strategies, ensure that a child can compensate the nature's shortcomings or caused by environment .

This is because sometimes is easy to put away the legacies that parents give their children genetically speaking, because it is controversial to talk about whether the role of the environment is more or less important than the genes (Velázquez, 2004). It is known that genes contribute much to the development, but the environment exacerbates or represses this input. To the end of the day, If how can we be  geniuses of music if we don't have access to a musical instrument?, why do certain activities are easier than others?, Why schools aren't able to create geniuses?. 

In order to answer all those questions, it would be interesting to explain a bit of history, to mention that studies on the genetic relationships began in the year of 1900 with some research from someone called Mendel, however is interesting to note that Mendel carried out his discoveries almost without a previous research history.

 

  The history of prior knowledge to Mendel studies dating back to biblical times, as in genesis, a reference that Jacob, employed a method is presented for their sheep and goats raised mottled offspring (Strathern, 1999), bt it was not until  1694, when Camerarius reported the existence of sexes in plants and carried out the first experiments on pollination.  

Years later, entre1761 and 1767 Kölreuter, had done  research on hereditary mechanisms using plants,  however, the findings of this research appeared to confirm the current genetic theories at the time (mixed bloods), since the intersection between different varieties of Nicotiana (Nicotiana tabacum is a herbaceous perennial plant, of the family of the Solanaceae, whose leaves occurs most of the tobacco consumed in the world today), originating a hybrid of intermediate appearance between the parents which concluded this was due to two factors that each parent contributed in the same proportion to the characteristics of the offspring. The factors found by Mendel is what we currently know as genes (Strathern, 1999) .

Between 1822 and 1824, three independent researchers, Knight, Goss and Seton, realized studies based on pea (peas), discovering the dominance of some characters in generation 1 and segregation of several hereditary features in generation 2; However, do not they studied later generations or the numerical distribution of the characteristics of each generation, so it was not possible to extend the data from their studies.

Returning with Mendel, it has been written that he was fond of plants and to improve crops, although there is evidence that initially worked with mice, activity that seemed somewhat out of place to their superiors, for what made a change of experimental material to over 14 species of plants (Mendel said in any writing that he did not believe that his superiors knew that plants have sex). 

The pea, plant that finally worked, is a hermaphroditic species which has no sex chromosomes and it is easy to cut the stamens, avoiding in this way the self fertilization. Traits studied in such plants by Mendel are stable, although not studied intermediate conditions. For the form of the seed employed 253 hybrid (filial generation 1, F1), which had been obtained from a cross between the smooth seed plants and plants of rough seed, which originated only smooth phenotype, and is inferred a single genetic formula (genotype, Ll). But when the hybrids are crossed, it obtained 7324 seeds, of which 5474 were smooth and rough skin 1850, which somewhat complicated first finds, this generation called it subsidiary 2, F2 (Morgado, 2001; Barahona, Suarez and Martínez, 2001).

However, despite all the essential knowledge to explain the genetic mechanisms, most of the information for your understanding was obtained in years after Mendel, with the discovery of the desoxyribonucleic acid (DNA) carried out by Johann Friedrich Miescher in 1868; nucleic acids name are due to Richard Altmann, who thus called them in 1879.

But in this historic journey, it's not possible to forget the findings of Watson and Crick, doctors who allowed to know that the genetic information is contained in the molecular structure of desoxyribonucleic acid (DNA) which is found on the inside of a nucleus of the cell, in structures called chromosomes. However their findings were made possible the work of Rosalind Franklin who was an expert in x-ray crystallography and that thanks to her work was possible to elucidate the structure of the DNA double helix. 

Thanks to the joint work of these researchers from Cambridge, is found that desoxyribonucleic acid is a type of macromolecule that is part of all living cells and that there is contained the genetic information necessary for the development and operation of known living organisms and some viruses, being responsible for its transmission of heritable traits to the next generation. Within the DNA is very organized and associated with different proteins, which forms the structure known as chromatin (Watson, 2000).

References: 

Barahona, A., Suárez, E. y Martínez, S. (2001) Filosofía e historia de la biología. México. Facultad de Ciencias. UNAM. 

Kaback, DB. (2013)  The modest beginning of one genome project. Genetics. 194 (2) 291-299.

Morgado, E. (2001) ¿Cuán Mendeliana es la patología genética humana?. Clínica y Ciencia vol. 1 Nº 3. 48-59.

 

Strathern, P. (1999) Crick, Watson y el ADN. Siglo Veintiuno Editores. España.

Vásquez  Laslop, M. y Velázquez Arellano, A. (2004) Genómica y el desarrollo de un nuevo individuo. En A. Velazquez (2004) Lo que somos y el genoma humano: des-velando nuestra identidad. Ediciones científicas universitarias. UNAM. FCE.

Watson, J. (2000) La doble hélice. Alianza Editorial. Madrid.

Study of the brain through images, cytoarchitecture and electrical activity

To continue our  journey around the annals of the history of the study of the brain, is worth mentioning that the neuroanatomy has undergone revolutionary changes in the last decades. That leap has been made possible thanks to the introduction of new imaging techniques such as: X-Ray computed tomography (CT, also called computed tomography CT), (PET) Positron Emission Tomography and Magnetic Resonance Imaging (MRI), thanks all these tools, it is possible to observe the structure and activity of the brain in unprecedented detail.

All those datas, specially volumetric and structural studies, CT and MRI are of crucial importance to understand brain differences and give answer to many questions, specially about neuro degenerative diseases (Allen, Bruss and Damasio, 2005). 

However, this neuro technological revolution did not begin from nothing or yesterday, all these amazing possibilities probably began  in 1783 with physician Luigi Galvani who was a passionate about anatomy,  and who had the idea of using electricity to move the leg of a dead frog. Does that sounds like Frankenstein?,  what was this idea of moving a leg of a dead frog?,  well, he began efforts to stimulate and visualize neural activity, and some explain this open a door to  analyze living brains now.

Many years later, in 1937, a neuroscientist Charles Sherrington could see points of light signals in neuronal activity, this surprised to a Spanish physiologist,  Jose Delgado, and  he used radio waves to study the brain of a bull in 1963.

But it was not until 1971 that voltage fluorescent studies begin to become popular, and during decade of  1980 with the fluorescent dye, it was possible to see how calcium concentration changes while it's synthesized in a cell, and this  opened doors for the study of the brain on a larger scale (Miesenbock, 2008).

I can't forget during  this tour, including another researcher that made important contributions to the study of the brain, so I must remember to Korbinian Broadman, who conducted research that allowed to distinguish 52 brain regions, thanks to his studies on cerebral cytoarchitecture made on histological samples that permitted find anatomical definitions of different brains, and his studies currently  are known as  areas of Broadman which are used to mapping the brain, since they have been associated with specific activities and brain functions  (Kandel, Schwartz & Jessel, 2000).

Among the researchers that devoted his time to understand the functions relate to anatomical  Broadmann's areas there is a name, Wilder Penfield, who was a Canadian neurosurgeon and during his surgeries he stimulated with an electric pulse small points on the surface of the brain at the same time he asked to patient if he or she  felt something (this was necessary to determine exactly which region he had to operate). 

He found out that when different regions of the brain are stimulated in this way, the patient could have different perceptions (Harrison, Ayling & Murphy, 2012). For example, when it was stimulated the occipital lobe, patient saw flashes of light, but if it was stimulated  the parietal area, persons could heard buzzing, or maybe noticed tingling in any part of the skin, or maybe if stimulation was done in another region the patient begin moving any part of the body. 

Based on these observations, Penfield made a neurocortex map,  since  he could find where each sensory modality was represented in a specific part of the cerebral cortex, and he figured out it was not only possible to relate  a cortical region for each sensory modality, but that each part of the body had assigned to a specific region in the cortex, but on the opposite side of the body; for example a patient responded to a  electrical  stimulation on the left motor cortex with a movement of right leg. 

Therefore all his research made  possible to recognize areas on the surface of the cerebral cortex and relate them to different processes, finding in each patient  areas  where it was possible to recognize a specific taste, a vivid childhood memory or the fragment of a long-forgotten melody (Sagan, 2003; Shreeve, 2005; Library of archives of Canada, 2009). 

One of the reported cases, is about a patient who during a brain surgery said, he could  listened with luxury of detail, a interpretation of a composition of orchestral when it stimulated an area specified in his brain with an electrode. Other patients experienced a specific emotion, a sense of familiarity or the full memory of an experience of childhood, all simultaneously, forgetting the fact they were in an operating room talking to the surgeon. 

Some patients explained these memories as small dreams, but did not appear in them the symbolism characteristic of  a reverie (Shepperd, 2004). In the specific case of electrical stimulation of the occipital lobe, which is related to the vision, a patient said to be seeing butterflies flying around, so real and palpable, that even lying on the operating table, stretched out the hand to catch them (Sagan, 2003). 

All this experiences gave a good idea how the brain is divided into areas and allowed to map and  understand much better those parcels of information processing.

 However, even though there have been isolated area and process specific, neuroscience still cannot understand how it is possible to carry out the processing of information and the storage and handling of data that day to allow us to understand the environment and adapt to it, and I think the main question of neuroscience is: how do electric and chemical impulses become subjective experiences?.

References:

Allen, J.; Bruss, j. & Damasio, H. (2005) structure of the human brain. Research and science. 23 - January. 68-75.

Harrison TC., Ayling OGS, Murphy, TH. (2012) Cortical Disctinct circuit mechanisms for complex forelimb movement motor and map topography. Neuron. 72 (2) 397-409.

Kandel, E.; J.H Schwartz, Jessell, t. (2000) h Principles of Neural Science. New York: McGraw-Hill.

Library Archives of Canada (2009) Famous Canadian Physicians. (Available online): http://www.collectionscanada.gc.ca/physicians/030002-2400-e.html.

Miesenbock, g. (2008) Lighting up the brain. Scientific American . Vol. 299. NUM. 4 34-43.

Sagan, C. (2003) the Dragons of Eden: speculations on the evolution of human intelligence. Barcelona. Criticism.

Shepherd, g. (2004) The synaptic organization of the brain. Oxford, University press.

Shreeve, j. (2005) Cornina complet brain: she is all... is here. National Geographic.  207  (3) 6-12.