How is behavioral genetics studied

Monozygotic twins occur when a single zygote or fertilized egg splits apart in the first two weeks of development. The result is the creation of two separate but genetically identical offspring. About one-third of twins are monozygotic twins. Monozygotic twins occur in birthing at a rate of about 3 in every deliveries worldwide about 0. Monozygotic twins are genetically nearly identical and they are always the same sex unless there has been a mutation during development.

The children of monozygotic twins test genetically as half-siblings or full siblings, if a pair of monozygotic twins reproduces with another pair of identical twins or with the same person , rather than first cousins. Sometimes two eggs or ova are released and fertilized by two separate sperm.

The result is dizygotic or fraternal twins. About two-thirds of twins are dizygotic. These two individuals share the same amount of genetic material as would any two children from the same mother and father. Older mothers are more likely to have dizygotic twins than are younger mothers and couples who use fertility drugs are also more likely to give birth to dizygotic twins. Consequently, there has been an increase in the number of fraternal twins in recent years Bortolus et al.

In vitro fertilization IVF techniques are more likely to create dizygotic twins. For IVF deliveries, there are nearly 21 pairs of twins for every 1, The amniotic sac also called the bag of waters or the membranes , is a thin but tough transparent pair of membranes that hold a developing embryo and later fetus until shortly before birth. Fraternal twins each have their own placenta and own amniotic sac. Figure 1. Dizygotic twins come from two separately fertilized eggs and have their own placentas and amniotic sacs.

This is known as placentation. Figure 2. Conjoined twins are monozygotic twins whose bodies are joined together during pregnancy. This occurs when the zygote starts to split after day 12 following fertilization and fails to separate completely. This condition occurs in about 1 in 50, human pregnancies. Most conjoined twins are now evaluated for surgery to attempt to separate them into separate functional bodies.

The degree of difficulty rises if a vital organ or structure is shared between twins, such as the brain, heart or liver.

You begin to use your environment; you hang out with people who are like-minded. The one grandchild will be hanging out with other kids who read books, who are interested in intellectual conversations.

Language development has been studied a lot. An interesting question that behavioural geneticists have begun to address is about learning the second language, how does that fit with it. It turns out that many of the same genes are involved. People who are good at verbal measures in their first language will tend to be pretty good in a second language.

But there are some specific genetic factors. The bottom line of that research is that about a third of the genetic influences on learning a second language are overlap with the ability to learn first language, but about a third of the genetic effects are different, and then about a third overlap with just general intelligence. Much of psychology and the life sciences is not asking about individual differences, they are just asking about universal questions about the human species.

A real transformation of research in this area up until now people have been concerned about just simply asking whether genetics is important and then asking how important.

That question has been pretty much answered across-the-board. We go beyond that to ask questions about the development, about the relationship between traits like a big issue right now is in psychopathology and mental illness there is all these different diagnoses.

Neural Basis of Social Interaction Neuropsychologist Chris Frith on mirror neurons, perception of biological motion, and mentalizing It turns out that genetic effects are pretty much the same that is the same genes are causing many of these so-called different disorders.

A third area the first — development, the second — multivariate is the interplay between genes and environment. So, if nature and nurture are important a lot of researchers are interested in how they work together, the interplay, the correlation and the interaction between genes and environment as they affect development.

DNA is the best tool we have for predicting problems at which allows us to intervene to prevent problems which is the way all of medicine is going. The excitement now is about trying to find these genes and we are at the turning point where we are beginning to find genes which will allow us to make individual predictions about genetic risk and resilience, vulnerability and strength which will eventually allow us to predict problems and then hopefully begin to prevent them.

DNA and Behavioral Genetics. Behavioral geneticist Robert Plomin on the prediction of GCSE results, reading disability, and the heritability of intelligence. Brain Training. Neuropsychologist Barbara Sahakian on cognitive training, areas of the brain that get affected in Alzheimer's disease, and improving cognitive function through games.

Neural Basis of Social Interaction. Genetic influence on human psychological traits: A survey. Current Directions in Psychological Science Points out the extant literature demonstrating genetic effects on virtually all behavioral traits that have been studied.

This article takes the next step by questioning how specific genes interact with the environment to affect behavior.

Bouchard posits that the pervasiveness of heritability across traits may generalize to all species, not just humans.

Available online by subscription. DiLalla, Lisabeth Fisher, ed. Behavior genetics principles: Perspectives in development, personality, and psychopathology. Resulted from a festschrift for Professor Irving I. Gottesman, a pioneer in behavioral genetics research. Geared to researchers and students in the field. Kim, Yong-Kyu. Handbook of behavior genetics. New York: Springer. DOI: Intended for students of genetics, psychology, and psychiatry.

Chapters describe research in various areas of behavior including psychopathology, intelligence, and personality. Behavioral genetic relevance is discussed, as are cutting-edge methodologies and the directions these fields will take in the future.

Malouff, John M. Rooke, and Nicola S. Schutte, The heritability of human behavior: Results of aggregating meta-analyses.

Current Psychology A meta-analysis of the heritability of eight different behavioral characteristics across hundreds of twin and adoption studies. This review suggests that human behavior in general is approximately 41 percent heritable. The authors also identify possible moderators of genetic influence, which will be important for future studies to consider.

Rutter, Michael. Genes and behavior: Nature-nurture interplay explained. Malden, MA: Blackwell.