18 Genetics and Environment

Tabitha Panmei

Content Table

Learning outcome of the Module

1.      Introduction

2.      Genetic and Environmental Effects on Quantitative Traits

3.      Gene and Environment interactions

4.      Environmental Influences on Gene Activity

5.      Changes in the environment that impact survival of  individuals and species

6.      Genetic and Environmental influences on Human

7.      The Nature of Genetic influence

a)      Cognitive abilities

b)      Personality and Interest

8.      Effects of Heredity and Environment on our personality

a)      Heredity

b)      Environment

9.      Nature and Nurture Influence Human Development

10.  Information of the debate in genetic and environment

Learning outcome of the module

• After seeing this module, you would understand the interaction of genetic and environment.
• You would know how genes influence through environment.
• You may understand the effect caused by heredity and environment.
• We can see the history of debates bring up by different author about the nature (gene) and Nurture (environment).

1.    Introduction

The study of genes that they are and how they work is known as Genetics. The living organism which inside the cell to control how living organisms inherit features from their ancestors is gene; for example, children look like their parents because they inherited with their parents’ genes. Genetics explain how the features of parents pass to their children from generation to the next generation.

In genetics, the feature of a living thing is known as trait. Some traits of an organism’s morphology are its form and structure; like eye-color, height and weight. Other sorts of traits are not easily seen like blood types or resistance to diseases. It is a complicated way our genes and environment interact to produce a different trait. In example, the general design of a tiger’s stripes is inherited, whereas the actual stripe pattern on an individual tiger is influenced by environmental factor from where they live.

Genes are made up DNA which copied and inherited across generations to next generation. The DNA which are present in our body are made up of nucleotide, simple units that line up in a particular order within a molecule and it carry genetic information’s like how the order of letter on a page of text carries information. It have own language which is known as genetic code, that allows the genetic machinery to read the information in the genes in triplet sets of codons.

A gene cannot give same exact information between the one organism and another, and also different copies of a gene do not always give exactly the same instructions. The uniqueness of each form of a single gene is known an allele. In example, one allele for the gene for hair color could instruct the body to produce a lot of pigment, producing black hair, while a different allele of the same gene might give garbled instructions that fail to produce any pigment, giving white hair. Mutations are in random changes in genes, and can produce new alleles. Mutations produce new traits, such as when mutations to an allele for black hair produce a new allele for white hair. This appearance of new traits in organism is important in study of evolution.

2. Genetic and Environmental Effects on Quantitative Traits

We found that characteristics of an organism of living thing are determined by his/her genetic endowment that is gene received from the earlier generation. Thus a person is born with a fixed genetic endowment but its phenotypic express depends on the environment in which they grow. Genes cannot work in a vacuum nor can the environment shape an organism without genes. They have unique combination of genes functioning in single environment. Thus the interaction of heredity and environment is significant in shaping the expression of phenotype showing in individual. It referred to Nature verses Nurture interaction between heredity and environment which in final analysis are the determinants of the biological characters of the individual, and both are equally important.

For example, in case of blood groups, the differences between individuals are genetic origin. Even such traits require an environment before they develop. Similarly, when differences are entirely environmental in origin underlying genetic basis concerned on character. The RBC count of individuals can also depend on the environment which they live. Likewise, the heredity determines the capacity of individuals to vary the concentration of RBCs by atmospheric oxygen tension. So, the differences of individual may have both genetic and environmental factor. Some of the important effects are nutritional state and other climatic factors. Uneasy environment can produce effects like abnormal gene. The most important is similarity in effect of polygenic determination and normal environmental variation. It depends not only on environment variation but also on genotype interacting. Twin studies is the best assessed for the example of relative interaction between heredity and environment. It plays a major role in the history of human genetics. Most of the conclusion in human behavioral genetics is based on twin study data.

3.    Gene and Environment interactions

·         Identical twins find similar friends.

·         Identical twins treated more similarly (or differently) than fraternal twins.

·         It is not nature vs. nurture, but the interaction of nature and nurture that drives development.

·         Environmental risks that interact with genes to predict vulnerability and resilience

·         Measured Gene-Environment Interactions and Mechanisms Promoting Resilient Development.

Fig 1.1 showing interaction of gene and environment:

4.    Environmental Influences on Gene Activity

• Antenatal depression in pregnant women due to higher methylation.
• Suicide victims have more methyl groups in glucocorticoid receptor genes.
• Higher methylation, increased susceptibility to stress in gene expression in older twins associated with greater in methylation.

5.    Changes in the environment that impact survival of individuals and species

• UV light exposer.
• Exposure to radiation such as uranium mining, atomic bombs, medical work with radiation.
• Human activity involving chemical released in soil, air, and water.
• Legal and illegal drugs.
• Availability of resources such as food, clean water, space, and shelter.
• Climatic changes.
• Human activity (habitat destruction and pollution).
• Natural disasters (flood and volcano).
• Parasites, bacteria, and viruses.

6.    Genetic and Environmental influences on Human behavioral

It is difficult to determine whether genetics (“nature”) or the environment (“nurture”) has a stronger influence on behavior, and it is largely believed that human behavior is an intricate result of both. For example, a preference for a particular food could be genetically based, it could be because you ate it growing up, or it could be a combination of both. In most cases, behavior is the result of a dynamic interplay between nature and nurture. Studies on identical twins are often used to determine what can be attributed to genetic influences and what can be attributed to environmental influences. Identical twins share the same genotype, meaning their genetic makeup is the same. Researchers have discovered, however, that the phenotype (or the observable expression of a gene) of identical twins grows apart as they age. Our genes influence how we respond to our environment, and at the same time the expression of our genes are changed by the environment around us; therefore the relationship between genetic and environmental influences cannot be easily separated. Human behavior hunts to identify and characterize in both the genetic and the environment sources for individual differences in human behavior. This topic has not been reviewed in the series since 25 years pasts. We have taken a broader perspective that might be customary, electing to consider the behavioral genetic research, although it emphasis on research published in the past 5 years. The reader want to consult the recent general review of this area, as well as specific reviews of behavioral genetic research on crime and violence, behavioral medicine, psychiatric genetics, intelligence, and personality.

7. The Nature of Genetic influences

There are two way which nature of genetic influence:

a) Cognitive abilities– It is more focus on behavioral genetic perspective and psychological trait. Some of the example is given below.

•  Psychopathology- It studies the behavioral disorder in twin and adoption.
• Schizophrenia- It studies the linkage to identify several chromosomal regions as candidates for containing a schizophrenia susceptibility locus.
• Manic Depression – It studies the depressive illness in linked 14 different chromosomal regions, but none of which can be confirmed till now.
• Alchoholism- It studies to identify single genes contributing to risk of alcoholism have used the association method. It involved in the metabolism of alcohol, aldehyde dehydrogenase and alcohol dehydrogenase. Approximately 50% of individuals of East Asian ancestry inherit inactivity of mitochondrial form ALDH.

b) Personality and Interest- It utilized most widely scheme for characterizing personality traits is the big five- extraversion, agreeableness, conscientiousness, neuroticism, and openness.

8.      Effects of Heredity and Environment on our personality

Every individual have a different from other. In various way, either in physical or psychological. Even the twins are no exception to this. They are different in some aspects on other. If we look at people from psychological point, these differences are quite obvious. Even the children from one parent differ and differ from parents. They will have some similarities with some forefathers on grand-parent instead of their parents.

The basic effects of personality development are heredity and environment.

a) Heredity- In heredity it refers to the genetic inheritance received by every individual at the same of conception. The origin of human life can be traced to a single cell called zygote formed by the union of sperm and ovum. The sperm and ovum contain 23 pairs of chromosomes out of which one will be sex determining chromosome. Female have 23 pairs of XX chromosomes and male have 22 pairs of XX and 2 single, represented as XY. Father lead to male offspring, XX from both parents give rise to female. Each chromosome has innumerable genes. These genes are the real determiners of heredity characteristics. Which pass from one generation to the next? At the time of conception, the genes from chromosomes of both the father and mother fuse together and determine the traits of the offspring to produce a new one. The physical characteristics are change due to the change in the genes transmitted. Fraternal twins are different from each other, because they are born out from different genes. However, we can find more resemblances in identical twins because they are born out of monozygotic.

b) Environment- In environment, it is studying on the fields of society and even the whole world. The word environment is restricted to environment within mother’s womb and just born, as well as the environment around the individual. Environment also plays a very important role in determining the behavior and personality development of an individual. The environmental influences are than which act upon the organism at the earlier stages of development before and after birth. In environment it includes the extrinsic forces, influences and conditions which affect the life, nature, behavior, the growth, development and maturation of living organism

For example, we can say the zygote is surrounded by a jelly like substance known as cytoplasm. The cytoplasm is an intracellular environment which influences the development. Life begins with single cells formed and a new internal environment comes into existence. Foetus develops the endocrine glands which gives rise to another intracellular environment. Hormones are necessary for normal development, but defects in hormone secretion over or under secretion may lead to congenital deformities.

9.    Nature and Nurture Influence Human Development

In terms of nature and nurture, it is related to the relative importance of an individual’s innate qualities as compared to an individual’s personal experiences which causes differences in individual, especially in the traits of behavioral. The assonant express on “nature and nurture” in English has been use since the time of Queen Elizabeth and goes back to medieval French. There are two combination concepts of nature and nurture influence complementary is from ancient time. The phrase given in modern sense by English Victorious polymath Francis Galton discuss the influence of heredity and environment on social advancement, Galton was influenced by the book called “On the Origin of Species written” by his half-cousin, Charles Darwin. It view that humans acquire all or almost all their behavioral traits from “nurture” was termed tabula rasa (blank slate) by John Locke in 1690. A “blank slate view” in human development psychology assumed that human behavioral traits develop exclusively from environmental influences, which was widely held during 20th century. The debate between “blank-slate” denial of the influence of heritability, but the view admitting both environmental and heritable traits, has often been cast in terms of nature versus nurture. These two conflicting approaches to human development was the core of an ideological dispute over research agendas during the half of the 20th century. Both nature and nurture factors were found to be contributed substantially, often in an extricable manner, such views were seen as naive or outdated by most scholars of human development by the 2000s. In their survey in 2014, scientist finds out some of the written dichotomy of nature versus nurture. In the fields of research, the scientists find out close feedback loops on “nature” and “nurture” influence one another constantly, and in other fields, but till now it is unclear about the dividing line between an inherited and an acquired trait.

10. Information of the debate in genetic and environment

John Locke (1690): He concerned about Human by often cited as the foundational document of “blank slate” view. Locke was criticizing René Descartes’ by claiming an innate idea of God universal to humanity and his view was harshly criticized in his own time.

Anthony Ashley-Cooper, 3rd Earl of Shaftesbury: They criticized Locke idea by denying the possibility of any innate ideas, which Locke “threw all order and virtue out of the world”, leading to total moral relativism.

Leda  Cosmides,  John  Tooby  and William  James (1842–1910):  They  argued  by  giving  a comment human have more instincts than animal, and get more freedom of action in the result of 8

Genetics and Environment

having more psychological instincts. The question of “innate ideas” or “instincts” was of importance in the discussion of free will in moral philosophy. Philosopher cast in terms of “innate ideas” in 18th century by established the presence of universal virtue and prerequisite for objective morals.

J. L. Mackie: The argument was inverted in 20th century, as philosophers argued till now about the evolutionary of the origins of human behavioral traits which forces us to concede that there is no foundation for ethics while others treat ethics as a field in complete isolation from evolutionary considerations. There was increased in the interest of environment role in since early 20th century due to a reaction of strong focus on pure heredity in the wake of the success of Darwin’s theory of evolution. During 20th century, the social sciences also developed the project of studying the influence of culture in clean isolation from questions to “biology”.

Franz Boas’ (1911): He established a program that would dominate American anthropology for the next fifteen years in any of the given population, biology, language, material and symbolic culture, which are autonomous. After World War I, tool of twin studies was developed experimental setup intended to exclude all confounders based on inherited behavioral by traits. This study was designed to decompose the variability of a given trait in a given population into a genetic and an environmental component.

John B. Watson (1920s and 1930s): He established the school of purist behaviorism. Which will follow for a decades. Watson convinced the complete dominance of cultural influence over anything heritability contribution, by claiming” Give me a dozen healthy infants, well-formed, and my own specified world to bring them up in and I’ll guarantee to take any one at random and train him to become any type of specialist I might select – doctor, lawyer, artist, merchant-chief, beggar-man, thief, penchants, tendencies, abilities, vocations, and race of his ancestors.

Ashley Montagu( 1940s to 1960s): He was a notable proponent of this purist form of behaviorism which allowed no contribution from heredity whatsoever, “Man is man because he has no instincts, because everything he is and has become he has learned, acquired, from his own culture with the exception of the instinctoid reactions in infants to sudden withdrawals of support and to sudden loud noises, the human being is entirely instinct less.”

Calvin Hall (1951): He studied the dichotomy opposing nature to nurture ultimately fruitless. Robert Ardrey (1960s): He argued for innate attributes of human nature, especially concerning territoriality, in the widely-read African Genesis and the territorial imperative. Which organized opposition to Montagu’s kind of purist “blank-slatism” began to pick up in the 1970s, notably led by E. O. Wilson (On Human Nature 1979). Twin studies established in many cases, a significant heritable component.

Donald Brown (1980s): He contributes to the area of rectangle, its length or its width?” In a comparable avenue of research surveyed hundreds of anthropological studies from around the world and collected a set of cultural universals.

Genetics and Environment

Richard Lewontin, Steven Rose and Leon Kamin: They criticize “genetic determinism” from a Marxist framework, arguing “Science is the ultimate legitimator of bourgeois ideology if biological determinism is a weapon in the struggle between classes, then the universities are weapons factories, and their teaching and research faculties are the engineers, designers, and production workers. There debate shifted away from whether heritable traits exist to whether it was politically or ethically permissible to admit their existence. The authors deny by requesting that evolutionary inclinations could be discarded in ethical and political discussions regardless of whether they exist or not.

Watson or Montagu: Since 1990s, with the advances of genetic, they start studying heritability to perform easier and more numerous,. By the late 1990s, an overwhelming amount of evidence had accumulated that amounts to a reputation of the extreme forms of “blank-slatism”.

Harris : He criticized the point “parental upbringing which seems to matter less than previously thought” to the implicate “parents do not matter”.

Steven Pinker (2002): He presented the summarized of “The Blank Slate” on his book “The Modern Denial of Human Nature” which was instrumental in bringing attention of a wider public the paradigm shift away from the behavior purism of the 1940s to 1970s that had taken place over the preceding decades. Pinker portrays dedication to pure blank-slatism as an ideological dogma linked to two other dogmas found in the dominant view of human nature in the 20th century, which he termed “noble savage and ghost in the machine”. Pinker argues all the three dogmas were held onto for an extended period even in the face of evidence because they were seen as desirable in the sense that if any human trait is purely conditioned by culture, any undesired trait may be engineered away by purely cultural. Pinker focused on responsible for unduly repressing evidence to the contrary, notably the fear of political or ideological consequences.

Summary

• Genetics is the study of genes that they are and how they work. Genes are units inside a cell that control how living organismsinherit features from their ancestors; for example, children usually look like their parents because they have inherited their parents’ genes.
• Genetics tries to identify which features are inherited, and explain how these features pass from generation to generation.
• The allelic interactions known for a particular gene the genotype can be used to predict the phenotype. With one gene controlling a trait we have three possible genotypes, AA, Aa and aa and depending on the allelic interactions (dominance or incomplete dominance) we can have two or three phenotypes.
• Gene and Environment interactions in several ways.
• Epigenetics in Humans–Antenatal depression and anxiety- higher methylation
• Suicide victims – elevated methylation in hippocampus. More methyl groups in glucocorticoid receptor genes of abused. Umbilical cord blood, higher methylation and higher later cortisol, increased susceptibility to stress.Greater discordance in gene expression in older twins – associated with greater differences in methylation.
• Changes in the environment that impact survival of individuals and species.
• One of the longest, and at times most contentious, debates inWestern intellectual history concerns the relative influence of genetic and environmental factors on human behavioral differences, the so-called nature-nurture debate.
• Cognitive abilities- It has been more extensively studied from a behavioral genetic perspective than any other psychological trait.
• Personality and Interest– The most widely utilized scheme for characterizing personality traits is the Big Five- extraversion, agreeableness, conscientiousness, neuroticism, and openness.
• The basic effects sources of personality development are heredity and environment:

a) Heredity- It refers to the genetic inheritance received by every individual at the same of conception. The origin of every human life can be traced to a single cell called zygote.

b) Environment- It is the fields of society and even the whole world. The word environment is restricted to mean the environment within mother’s womb and just born, as well as the environment around the individual.

• The constrasts in terms nature and nurture relate to the relative importance of an individual’s innate qualities (nature in the sense of nativism or in-nativism) as compared to an individual’s personal experiences in causing individual differences, especially in behavioral traits.

Reference

 Suggested book

• Daniel L. Hartl and Andrew G. Clark (1997) Principles of Population Genetics. Library of Congress cataloging-in-Publication Data, 3rd edition
• Phillip W. Hedrick (2005) Genetics of Population. Jones and Barlett Publishers, Inc
• Matthew B. Hamilton (2009) Population Genetics. John Wiley and Sons Ltd, Publication.