Genetic+research-twin+studies,+family+studies+and+adoption+studies

=** ﻿ ﻿ Genetic research**=

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Researchers study twins because they share common genetic mateiral.



There are two types of twins: **monozygotic** (MZ) and **dizygotic** (DZ).

that splits into two. 2. These twins are of the same sex and should look very much alike. || 2. DZ twins will not be any closer genetically than brothers and sisters - they will have about 50 percent their genes in common. 3. These twins are not necessarily of the same sex. ||
 * Monogygotic (MZ) || 1. Monozygotic twins are genetically identical because they are formed from one fertilized egg
 * Dizygotic (DZ) || 1. Dizygotic means from two seperate eggs.
 * It should be the case that the higher the genetic relationship, the more similar individuals will be if the particular characteristic being investigated isinherited. In twins research, the correlation found is called the ** concordance rate. **

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Unlike twin studies, this is a more representative sample of the general population. A child inherits half its genes from the mother and father. It follows that ordinary brothers and sisters will share 50 percent of their genes with each other; grandparents will share 25 percent of their genes with their grandchildren; and first cousins will have 12.5 percent of their genes in common.



In family studies, these different degrees of genetic relatedness are compared with behavior. **The notion is that concordance rates will increase if heridability is high and vice versa.** For example, if the heritability of IQ is high, there should be a strong correlation in IQ between children and their mothers, but a weak correlation in IQ between second cousins, and very little, if any, between strangers.

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In principle, adoption studies allow the most direct comparison of genetic and environmental influences of behavior. Adopted or foster children generally share none of their genes with their adoptive parents, but they do share 50 percent of their genes with their natural mother. Therefore, if the heritability of a behavior is high and enviornment has little part to play, then the behavior of adopted children should correlate more strongly with the behavior of their natural mother than their adoptive mother. If, on the other hand,the environment has the strongest role to play, the reverse pattern should be found.




 * Adoption studies are often criticized as these children are not representative of the general population.
 * In addition, adoption agencies tend to use **selective placement** when findings homes for children, trying to place children with families who are similar in as many ways as possible to the natural parents.
 * In addition, adoption agencies tend to use **selective placement** when findings homes for children, trying to place children with families who are similar in as many ways as possible to the natural parents.

Overall, these approaches to the study of the relative influence of genetic make-up and the environment allow researchers to determine **the extent of genetic influence. It is clear that there is a correlation between several behaviors and genetic inheritance.**


 * Q: Explain why twin, adoption, and family studies are important for the argument of genetic makeup versus environmental influences?**

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