Topic 2: The origins of individual differences: nature vs nurture, Apuntes de Psicología Diferencial

¡Descarga Topic 2: The origins of individual differences: nature vs nurture y más Apuntes en PDF de Psicología Diferencial solo en Docsity! Topic 2. The origins of individual differences: nature vs nurture 09/10/18 What do you know about genes and behaviour? Steven Pinker: cognitive psychologist who works at Harvard university, The Blank Slate. Nature “world within the skins” vs nurture -> blank state, “table rasa” Nature: our genetics determine our behaviour. Our personality traits and abilities are in our “nature. Nurture: our environment and life experiences determine our behaviour. We are “nurtured” to behave in certain way. Will an adopted child be more like her biological parents or like her adoptive parents? How can we figure it out? What we know so far is that there are some traits that could be explained by their birth parents but it’s going to be tricky to figure it out in a clinical environment. Today we know that nature and nurture BOTH help shape our behaviour. 2.1 Where do we come from? We come from genetic determinism, who said that the genome determines the organism completely. Genotype=Phenotype. However, things are much more complicated than that. Genetic determinism is the simplistic idea that genes alone control human nature, this seem particularly insidious. E.g, the flowering of medical genetics in the 1950s led to the notorious, now-debunked idea that men with an extra Y chromosome (XYY genotype) were more aggressive. The molecular biology approach (Basic): DNA -> RNA -> PROTEIN. There is a unidirectional relationship in the expression of the info contained in genes. The DNA is transcribed to RNA that finally produces cellular action. The monogenic risk scores: a huge mistake The scientific advance this time is the genome-wide association study (GWAS). Invented in 1996, GWAS has gained massively in predictive power with the advent of ‘polygenic scores. Today you can find virus with DNA from RNA, even you can find proteins without DNA: Prions. So, the relationship between DNA, RNA and PROTEIN is not linear. We need to put environment into the equation. DNA -> RNA -> PROTEIN Environment -> active receptors -> signals -> turn on turn off genes 2.2 Epigenetics Stress Air War Etc. In fact, we are what happened to us. “… Any process that alters genes activity without changing DNA sequence (just functional activation), and leads to modifications that can be transmitted to daughter cells” Until recently, all of our characteristics were thought to be shaped by two different factors: Nature and Nurture. Epigenetics is a new field showing us that environment can modify our genes. Epigenetics: Functionally relevant changes to the genome that do not involve a change in the nucleotide sequences. Examples of mechanisms that produce such changes are: DNA methylation and histone modification, each of which alters how genes are expressed without altering the underlying DNA sequence. DNA is a long, ladder-shaped molecule: the famous ‘double-helix’ shape. Inside our cells, DNA contains all the information to make us grow and live. Genes are short sections or ‘chunks’ of DNA. Throughout your life, depending on specific conditions, a chemical called methyl attaches to genes. This chemical “switches” on or off only a section of your genes. This process of methylation is known as gene regulation. These chemical methyl attachments are called epigenetic tags. Think of them like switches that turn certain genes on or off, making them active or inactive. Your lifestyle determines which genes get “switched on” or “switched off”. What (and how much) you eat, how much you exercise, if you smoke, if you get a disease, if you experience stress… can all impact the way your genes are expressed. During fertilization, mom & dad’s DNA mixed in the egg. During the first days after fertilization, the epigenetic tags are erased… mostly. A small number of tags remain on the offspring’s DNA. This are called imprinted genes. Thus, the environment and lifestyle choice of the parents actually modify the genetic code of their offspring. DNA methylation could be added up to a DNA sequence and active or repress genes. The epigenome at a glance: DNA is wrapped around proteins called histones, both the DNA and histones are covered with chemical tags. The second layer of structure is called the epigenome, which shapes the physical structure of the genome. The DNA code is fixed for life, but the epigenome is flexible. Epigenetic tags react to signals of the outside world (diet, stress). An example: child abuse is an environmental factor that leaves and epigenetic mark on the brain. In a comparison of suicide victims who were abused or not, only the abused victims had an epigenetic tag (methyl groups) on the GR (glucocorticoid receptor) gene. Interestingly, the GR gene receives a similar epigenetic tag in rat pups who receive low quality care from their mothers. -> We’ve got associations between early life stress and gene methylation in children. 2.3 Molecular genetics How is the relationship among genetics and behaviour?