Genes

Genetics is the study of how traits
are passed on from parents to children. Genetics have been observed and studied
for a long time, constantly changing, evolving and challenging the research
throughout the years. Behavioral genetics is the study of the relative effects
of heredity and the environment on behavior and mental processes.

            In
order to understand behavioral genetics, it’s important to understand how and
where your genes and genetic make-up come from. In the beginning, we have
conception. At this time, each parent contributes chromosomes containing DNA.
DNA is the material in which is encrypted with genes. Humans have different
DNA, each having their own distinguished and unique features. However, this is
not the case for identical twins. The characteristics we possess are all
related to which genes we possess, controlling the transmission of traits. Some
traits, like a blood type or a widow’s peak, are only defined from one single
gene. Other traits, such as eye color or hair color, are polygenic, meaning
they are controlled by multiple genes, some of which are dominant and some that
are recessive.

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            Other
than studying and learning about how genes affect us as individuals, behavioral
genetics is also the study of how and when they are passed onto one generation
to another (Wiley, 2015). This is why scientists study identical and fraternal
twins. Identical twins share all of the same genes because they develop from
one egg, fertilized by one sperm. They are always the same sex and always have
the same genetic makeup. Fraternal twins are a little different. They only
share about half of their genes and are formed when two separate sperm
fertilize two separate eggs, this is why fraternal twins can be either the opposite
or the same sex. Ironically, fraternal twins are no more genetically similar
than non-twin siblings, they just share identical environments for the nine
months they are in the womb.

            Some
studies that test intelligences between twins show that identical twins have
more similar intelligence test scores than fraternal twins (Plomin &
Spinath, 2004; Trzaskowski et al., 2013) which would imply that the genetic
makeup of a person influences their intelligence. Since identical twins share
the same genetic makeup, it would make sense why their test scores are more
similar than fraternal twins.

            Twins,
however, are not the only family dynamic that researchers like to study. They
also study whether adopted children are more like their adoptive parents or
their biological parents. The adoptive parents control the home environment,
but the biological parents control the hereditary genes. This is an important
piece for researchers, as it can help further the knowledge and information
regarding which has a greater influence on a person; environment or genetics.
This study is also used to gather information for the “Nature vs Nurture”
debate. Using these family studies has helped prove that many traits and
disorders, like depression and/or intelligence are most strongly influenced by
genetics and not environment (Davies et al., 2011; Kang et al., 2012; Stein et
al., 2012).

            The
findings from these studies have allowed behavioral genetics to estimate the
heritability of various traits. Heritability is the statistic that provides a
percentage of variation in a population in regard to genetic factors versus
environment. There are however, misconceptions regarding genetics. There is a
lot of information that can be misconstrued, leading to false information or
misunderstandings. It is important to remember the following three cautions
when reading hereditability estimates; (1) heritability estimates do not apply
to individuals, but apply to groups, (2) genes and the environment are
interactive and inseparable and (3) genetic traits are not fixed and can vary
(Wiley, 2015).

             Height has one of the highest heritability
estimates, but your own height may vary in regard to your parents and/or your siblings
because of the individual combination of genes each person has (with an
exception to identical twins). It is impossible to predict a single
individual’s height from heritability, but you can make an estimate for the
group as a whole. It is also important to remember that genes have a strong
influence on disease and behavior, but genetic studies do not reflect how an
environment modification may change the outcome. For example, if you inherit a
possible genetic predisposition for cancer or diabetes, you may improve your
odds of not acquiring that trait by changing your lifestyle or taking
precautions.

            Behavioral
genetics and the study of such, gives scientists and researchers vital
information regarding how traits and genes work, how they are passed down from
generation to generation and how they affect both individuals and groups alike.
This is also why studying twins and other family dynamics like adoptive
families and siblings are so important. It gives researchers so much
information when it comes to how genetics, heredity and traits work. Behavioral
genetics give some insight to the ‘Nature vs Nurture’ debate and can be used to
understand and treat many different health problems in our world today. 

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