Chapter 2

Question 1

What are the key factors for studying hereditary factors of development?

Answer 1

Genotypes: coded by DNA
Phenotypes: interactions between genes and environments – physical, behavioural, psychological

Question 2

What was the Jim twins case and what did it reveal?

Answer 2

2 identical twins were separated at birth and reunited at age 39. They found many social and personal similarities. While some of them could have been coincidence, factors such as their likes and dislikes that may have led them there could have been genetic.

Question 3

What are sex chromosome-linked traits?

Answer 3

Controlled by genes located on the X or Y chromosomes— rather than the autosomes.

EXAMPLE: Haemophilia is an X-linked recessive disorder, so males express the condition with one haemophilia allele, while females with one allele are carriers because the normal allele is dominant.

Question 4

What is single gene inheritance?

Answer 4

A single gene controls the expression of a trait. Dominant alleles are expressed in the phenotype, or physical appearance, of an organism, while recessive alleles are only expressed when two copies are present.

Question 5

What are homozygous, heterozygous and incomplete dominance of alleles?

Answer 5

HOMOZYGOUS: two identical alleles for a trait (both blue eyes = blue eyed kid)

HETEROZYGOUS: Two different alleles for a trait dominant allele overtakes (curly + straight allele = curly hair)

INCOMPLETE: a dominant allele does not completely mask the effects of a recessive allele, and the organism shows a blending of both alleles (curly + straight allele = curly hair)

Question 6

What is meant by “behavioural genotypes reflect polygenetic inheritance”?

Answer 6

Human behaviours are influenced by many genes plus environment rather than one “behaviour gene.”

Question 7

How do we study behavioural genetics with twin studies?

Answer 7

Monozygotic twins are central because they have the same genotype.

Dizygotic twins can be studied to isolate the effect of environment without genotype.

Question 8

What is the concept of epigenesis in understanding genes alongside behaviour?

Answer 8

The multiple levels of the environment that drive development

Gene –> cellular environment –> individual’s behaviour –> family influences –> cultural influences

Question 9

What is the concept of reaction rage in understanding genes alongside behaviour?

Answer 9

The same genotype can produce a range of phenotypes in reaction to the environment. Your genes determine a minimum and maximum limit of effect environment may have.

Question 10

To what extent is behaviour influenced by genetic heritability or environment from parents?

Answer 10

• Parent genes impact child’s genes which impact child’s environment.
• Parent genes directly impact child’s environment (maybe through niche-picking too)
• Child’s genes impact child’s phenotype which have a reciprocal relationship with the child’s environment

Question 11

What is niche-picking?

Answer 11

Deliberately seeking environments that fit one’s hereditary. Genes influence your preferences and abilities, so as you grow older, you choose environments that suit those traits (ex: your major). This reinforces your gene expression.

Question 12

What are non-shared environmental influences?

Answer 12

Factors that cause differences among siblings because parents don’t provide the exact same environments for all of their children. (EX: gender socialization).

While parents do create environment, the child also provides their own environment through their choices.

Question 13

In “Why delayed onset of mental illness? Genes impact suspect brain areas late”

(1) What kind of study did the researchers perform?

(2) What did the researchers find regarding the relevance of considering age when assessing heredity of brain and behavioural phenotypes?

Answer 13

1) A twin study

2) Parts of the brain that are more heritable changes a lot throughout life stages, particularly adolescence because they become expressed more or take longer to develop thus they show up later