Lecture 8: Biology and Behaviour

Question 1

DNA

Answer 1

deoxyribonucleic acid. It is the molecule that carries the biochemical instructions involved in the formation and functioning of an organism

Question 2

Gene

Answer 2

sections of chromosomes and portions of DNA. Basic unit of heredity in all living things.

Question 3

Chromosome

Answer 3

thread-like molecules made up of DNA, containing many genes

Question 4

Genome

Answer 4

the complete set of genes in any organism (human genome project –mapping the entire human genome)

Question 5

What is DNA made out of

Answer 5

DNA is made of two linked strands that wind around each other in a double helix formation. It has two carbohydrate or sugar backbones – base pairs of protein in the middle

Question 6

Human genome project

Answer 6

Human genome project – international project with goal of mapping the entire sequence of human genes

Question 7

Genotype

Answer 7

the genetic material an individual inherits

Question 8

Phenotype

Answer 8

the observable expression of the genotype, including body characteristics and behaviour

Question 9

Environment

Answer 9

includes every aspect of the individual, and his or her surroundings, other than genes

Question 10

Parent genotype to child genotype

Answer 10

Genetic material is passed on as chromosomes- long, threadlike molecules made up of DNA:

Carry all of the biochemical instructions involved in the formation and functioning of an organism

Genes are sections of chromosomes that are the basic units of heredity for all living things

Karyotype: an individual’s complete set of chromosomes ->

Karyotype of how each of the chromosomes (23 pairs) come together

Question 11

Mechanisms contributing to genetic diversity

Answer 11

Mutation: A change in a section of DNA. Caused by random or environmental factors (e.g., teratogens)

Random assortment: The shuffling of the 23 pairs of chromosomes in the sperm and egg; chance determines which member of the pair goes into the new sperm and egg

Crossing over: The process by which sections of DNA switch from one chromosome to another during meiosis, further increasing genetic variability

Question 12

Child genotype- phenotype

Answer 12

Although every cell in your body contains copies of all the genes you received from your parents, only some of those genes are expressed.

Regulator genes Largely control the continuous switching on and off of genes that underlie development across the lifespan

A given gene influences development and behaviour only when it is turned on

Important for healthy development

Question 13

Gene expression - Alleles

Answer 13

About a third of human genes have two or more different forms, known as alleles.

The dominant allele is the form of the gene that is expressed if present.

The recessive allele is not expressed if a dominant allele (that is of the same role) is present.

A person who inherits two of the same alleles for a trait is described as homozygous.- two recessive or two dominant.

A person who inherits two different alleles for a trait is described as heterozygous.(one of each)

Question 14

Mendelian inheritance patterns

Answer 14

Biological parents

B- dominant gene for brown hair

b-recessive gene for blond hair

Heterozygous

Children can have brown or blond hair

Question 15

The “male” disadvantage

Answer 15

The Y chromosome has only about a third as many genes on it as the X chromosome

Many alleles on the X chromosome do not have a corresponding allele on the Y chromosome that could suppress the action.

Therefore, individuals with only one x-chromosome (as suppose to having two) are more likely to suffer a variety of inherited disorders caused by recessive alleles on the X chromosome (e.g., colour blindness)

Question 16

Genetic origins of human diseases and disorders

Answer 16

Over 5,000 human diseases and disorders are presently known to have genetic origins

Recessive gene: PKU, sickle-cell anaemia, cystic fibrosis

Single dominant gene: Huntington’s disease

Sex-linked inheritance: Fragile-X syndrome, haemophilia

Errors in meiosis (resulting in a zygote with fewer or more than the normal complement of chromosomes) – e.g., Down syndrome

Question 17

Down syndrome

Answer 17

Down syndrome (Trisomy 21)

21 st chromosome- 3 chromosomes instead of 2, causing down syndrome.

Question 18

Polygenic inheritance

Answer 18

The mendelian dominant-recessive pattern of inheritance pertains to relatively few human traits (e.g., hair colour, blood type etc.)

Many other traits are governed by more than one gene (e.g., height, intelligence…- not determined by one gene)

Polygenic inheritance applies to most traits and behaviours of interest to behavioural scientists

Question 19

The effects of environment on phenotype

Answer 19

A given genotype can develop differently in different environments - env meaning anything that is not the genetic info itself- everything around us

“Environment” relates to anything that is not the genetic information itself
This idea is expressed by the concept of the “norm of reaction

Question 20

Norm of reaction (Dobzhansky, 1955)

Answer 20

Refers to all the phenotypes that could theoretically result from a given genotype, in relation to all the environments in which it could survive and develop

Question 21

The case or PKU

Answer 21

Children with phenylketonuria (PKU)— a disorder that is related to a defective gene on chromosome 12—are unable to metabolise phenylalanine

Present in some foods such as sweeteners
With early diagnosis and a properly restricted diet, however, cognitive impairment resulting from PKU can be avoided

Genotype can result in different phenotypes depending on the environment

Question 22

Behaviour genetics research design

Answer 22

How variation in behaviour and development results from the combination of genetic and environmental factors

The family study is the mainstay of modern behaviour-genetics research.

Correlations between the measure of the trait in individuals with different relationships are examined to see if they are higher for individuals who:
Are genetically more similar
Share the same environment

Question 23

Types of family studies

Answer 23

Twin-Study Designs: Correlations for pairs of monozygotic twins (identical and share the same zygote) on a trait of interest are compared to those of dizygotic twins (non-identical twins)

Adoption Studies: Researchers examine whether adopted children are more like their biological or their adopted relatives (documentary Three Identical Strangers might be of interest)

Question 24

Minnesota study of twins reared apart

Answer 24

Located and studied twin siblings who have not met since they were infants

Begun 1979, longitudinal study (followed up individuals in different parts of their lives)

The team of investigators were struck by the similarities they found in traits like IQ, reaction to stress, and traditionalism

Also personality, hobbies, professions…

These similarities may be influenced by selective placement and similarities in fostering environments as well as by genetic factors

Question 25

Shared Environmental effects

Answer 25

Most obvious source of shared environment is growing up together in the same family
Behavioural geneticists, however, have found surprisingly little effect of shared environment on some aspects of development

Question 26

Non-shared environment

Answer 26

Non-shared environment effects include experiences unique to the individual

Siblings may have quite different experiences within the same family and their experiences outside the family may diverge sharply

The primary effect of non-shared environmental factors is to increase the differences among family members