College of Education

School of Continuing and Distance Education 2014/2015 – 2016/2017

PSYC 223

Research Methods

Session 6 – GENES AND BEHAVIOR

Lecturer: Dr. Adote Anum, Dept. of Psychology Contact Information: aanum@ug.edu.gh

Session Overview

• The role of genetics in behavior development has been studied extensively in psychology. To a large extent, human behavior is a result of interaction between genes which have been inherited from the parents and environment. In this session, we will focus on the principles that explain the influence of genes in behavior development. You will be introduced to the basic theory of genetics. You will learn about some important terminologies in genetics and behavior. You will also learn about the principles that guide sex determination and also learn about some disorders that occur when there are problems in the genetic processes during conception.

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Session Outline

The key topics to be covered in the session are as follows:

• Basic Principles in Genetics and hereditary

• Sex Determination

• Chromosomal Aberrations/Disorders

You are required to arrange your slides to reflect the outline provided, so that students know when topics start and end. This will also help the video editor breakdown your videos to reflect the sessions.

It is advised that you have a minimum of three or four topics (approximately 30 minutes per topic) so that your videos are broken down to explain the key topics and for easy referral by students.

You can divide a very broad topic to sub-topics where necessary

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Reading List

• Read Chapter One of Biological Psychology 9th Edition by J. W. Kalat; pages 12 - 20

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BASICS PRINCIPLES IN GENETICS Topic One

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• The laws of genetics were first derived by Gregor Mendel (1865 and 1866), who was a 19th century monk who’s laws form the theoretical basis of our understanding of the genetics of inheritance.

• Mendel planted and studied garden peas and derived a law known as Mendelian inheritance law.

• Mendel discovered that, when he crossed purebred white flower and purple flower pea plants (the parental or P generation), the result was not a blend. Rather than being a mix of the two, the offspring (known as the F1 generation) was purple-flowered

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Mendel’s Principles of Genetics

• Parental Generation

• Parental Gametes/traits

• F1 Genotype

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The Genetics of Behavior

• Genes are basic units of heredity that maintain their structural identity from one generation to another.

• Genes are aligned along chromosomes (strands of genes) and come in pairs.

The Genetics of Behavior

• A gene is a portion of a chromosome and is composed of deoxyribonucleic acid (DNA).

• DNA serves as a model for the synthesis of ribonucleic acid (RNA).

The Genetics of Behavior

• RNA is a single strand chemical that can serve as a model for the synthesis of proteins.

• Proteins determine the development of the body by:

• forming part of the structure of the body.

• serving as enzymes that serve as biological catalysts and regulate chemical reaction in the body.

Some Basic Terminologies

• Allelles

– one alternative form of a given allelic pair; tall and short are the alleles for the height of an individual

• Homozygote

– An individual which contains only one allele at the

allelic pair; for example DD is homozygous dominant and dd is homozygous recessive

• Heterozygote

– an individual which contains one of each member of the gene pair; for example the Dd heterozygote

Some Basic Terminologies

• Genotype – The full set of all the genes that an organism/individual possesses

• Phenotype – literally means "the form that is shown"; it is the outward, physical

appearance of a particular trait. The appearance of an organism that results from the interaction of genes with one another and with the environment

• Dominant – the allele that expresses itself at the expense of an alternate allele;

The member of the gene pair that is routinely expressed

• Recessive – an allele whose expression is suppressed in the presence of a

dominant allele

The relationship between Genes, Cells, and Behavior

Chromosomes and Genes

• Human somatic cells have 23 pairs of chromosomes

– One copy from the mother (X) and one copy from the father (Y)

– Autosomes: Pairs 1-22

– Sex chromosomes: Pair 23

Genes Proteins Cells Behavior

• Genes do not directly produce behaviors.

• Genes produce proteins that increase the probability that a behavior will develop under certain circumstances.

• Genes can also have an indirect affect.

– Genes can alter your environment by producing behaviors or traits that alter how people in your environment react to you.

The Genetics of Behavior

SEX DETERMINATION Topic Two

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The Genetics of Behavior

• Types of genes include:

– Autosomal genes - all genes except for sex- linked genes.

– Sex-linked genes - genes located on the sex chromosomes.

• In mammals, the sex chromosomes are designated X & Y.

– Females have two X chromosomes (XX).

– Males have an X and a Y chromosome (XY).

The Genetics of Behavior

• During conception females parent contribute an X chromosome and male parent contribute X or a Y chromosome.

• If an X chromosome is contributed by the male, the off-spring is female.

• If a Y chromosome is contributed by the male, the off-spring will be male.

• The Y chromosome contains genetic information (SRY) that turns the foetus into a male child.

The Genetics of Behavior

• The human Y chromosome has genes for 27 proteins

• The human X chromosome has genes for approximately 1500 proteins.

• Thus, sex-linked genes usually refer to X-linked genes. (Example: Red-green color deficiency, Hemophilia)

• Sex-limited genes are genes that are present in both sexes but mainly have an effect on one sex (Chest hair, breast size, etc.)

CHROMOSOME ABERRATION Topic Three

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Chromosomal Aberrations & Disorders

• A chromosome anomaly, abnormality, aberration, or mutation is a missing, extra, or irregular portion of chromosomal DNA.

• It can be from an unusual number of chromosomes (more or less than 2) or a structural abnormality in one or more chromosomes.

• Genetic disorders involve aberrations in part of a chromosome (or the entire chromosome).

• We will focus on some examples in this topic.

Selected Genetic Disorders

• We will describe the following Chromosome disorders:

– Huntington’s

– Down’s syndrome

– Turner’s syndrome

– Klinefelter’s syndrome

Huntington’s Chorea

• Huntington's Chorea, is an inherited, autosomal degenerative disorder of the Central Nervous System, caused by a dominant gene. – This means that everyone who inherits the gene from

one of his/her parents will develop the disease,

– It results in motor and cognitive disturbances – It characterized by hyperkinesias - abnormal, purposeless,

involuntary motor movements that can occur spontaneously or only when the patient is trying to do something

Trisomy 21 (Down Syndrome)

• Down’s Syndrome

– Chromosomal abnormality resulting in mental retardation and other abnormalities, usually caused by an extra chromosome 21 (trisomy 21)

– There is a total of 47 chromosomes instead of 46.

• It is a rare disorder (Incidence: 1:800)

• However the incidence increases with the age of mother, i.e., older mothers are more likely to have one

Down Syndrome - Physical features

• Short height • Slanting eyes • Severe mental deficiency with decline in the IQ with age • Deficit in social skills – delay in development • Flat and low nasal bridge • Malformed large ears • Broad short hands • Epicanthal folds of the eyes

– An epicanthal fold is skin of the upper eyelid that covers the inner corner of the eye

• Prominent and protruding tongue (scrotal tongue)

Down’s Syndrome – medical consequences

• Inability to reach normal growth and development

• Congenital heart defects in infants, early mortality

• Cardiac problems

• Renal anomalies

• Faster aging process and tendency to develop diseases of aging, such as Alzheimer's at a relatively early age.

Down’s Syndrome - treatment

• There is no specific treatment for Down syndrome.

• Treatment is available for the health problems that the person might have.

• They are placed in special education programs to help them with cognitive and social development

and

• To provide them with occupational skills

Turner’s Syndrome

• Turner’s syndrome (TS) is a condition in which a female is partly or completely missing an X chromosome.

• The physical features include a short and webbed neck, low-set ears, low hairline at the back of the neck and short in stature.

• Their intelligence is normal.

• They do not develop breasts, they do not have menstrual cycles and they do not have children

• Other features include heart defects, low thyroid hormone and problems with vision and hearing problems.

• Likeother chromosomal disorder, there is no treatment

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Klinefelter’s Syndrome

• Klinefelter syndrome (KS) occurs when a boy is born with one or more extra X chromosomes. – Also known as 47, XXY

• Symptoms are usually not observed until puberty. – They include, sterility, weak muscles, great height, poor

coordination, less body hair, small genitals, breast growth, and less interest in sex.

– Intelligence is usually normal; however, reading difficulties and problems with speech are more common.

– Symptoms are typically more severe if three or more X chromosomes are present

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References

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