Chapter 6

Question 1

What is a genome?

Answer 1

A genome refers to the complete set of genes an organism possesses.

Question 2

How many genes does the human genome approximately contain?

Answer 2

The human genome contains between 20,000 and 25,000 genes.

Question 3

How are the genes in the human genome organized?

Answer 3

All these genes are located on 23 pairs of chromosomes.

Question 4

What do the 23 pairs of chromosomes in the human genome represent metaphorically?

Answer 4

One way to think about the human genome is to consider it as a book containing 23 chapters, with each chapter being a chromosome pair.

Question 5

Where are the genes located within a cell?

Answer 5

The genes are located within the nucleus of each cell.

Question 6

Do red blood cells contain genes? Why or why not?

Answer 6

Red blood cells do not contain any genes because they lack a nucleus.

Question 7

How many copies of the genome does each human possess in their body?

Answer 7

Each human has roughly 100 trillion copies of our genome within our bodies.

Question 8

How do the number of genes humans possess compare to other species like mice and worms?

Answer 8

Although the number of genes humans possess is similar to the number estimated for mice and worms, human genes are decoded into proteins in a more variable manner than in other species.

Question 9

What field studies the genetic and environmental influences on individual differences in personality?

Answer 9

Behavioral genetics.

Question 10

What is eugenics, and why is it controversial?

Answer 10

Eugenics is the notion that we can design the future of the human species by fostering the reproduction of persons with certain traits and discouraging the reproduction of persons without those traits. It is controversial because of its ideological implications and potential for misuse.

Question 11

Can environmental factors influence genetic traits? Give an example.

Answer 11

Yes, finding that a personality characteristic has a genetic component does not mean that the environment is powerless to modify that characteristic. For example, height is largely genetic, but nutrition can significantly influence it.

Question 12

What percentage of individual differences in height can be attributed to genetic differences?

Answer 12

Genetic research has confirmed that roughly 90 percent of the individual differences in height are indeed due to genetic differences.

Question 13

Define heritability.

Answer 13

Heritability is a statistic that refers to the proportion of observed variance in a group of individuals that can be accounted for by genetic variance.

Question 14

What is the difference between phenotypic variance and genotypic variance?

Answer 14

Phenotypic variance refers to observed individual differences, such as in height, weight, or personality. Genotypic variance refers to individual differences in the total collection of genes possessed by each person.

Question 15

What does environmentality refer to in genetic research?

Answer 15

The percentage of the observed variance in a group of individuals that can be attributed to environmental (nongenetic) differences.

Question 16

Why is heritability considered an estimate rather than a definitive measure?

Answer 16

Heritability is an estimate because it depends on both the range of genetic differences and the range of environmental differences in a given population at a specific point in time.

Question 17

Name three methods used in behavioral genetics to study heritability.

Answer 17

Selective breeding with animals, family studies, and twin studies.

Question 18

Explain the difference between monozygotic (MZ) twins and dizygotic (DZ) twins.

Answer 18

Monozygotic (MZ) twins come from a single fertilized egg that divides into two, sharing 100% of their genes. Dizygotic (DZ) twins come from two separate fertilized eggs, sharing 50% of their genes.

Question 19

What is the equal environments assumption in twin studies?

Answer 19

The assumption that the environments experienced by identical twins are no more similar to each other than the environments experienced by fraternal twins.

Question 20

What can be inferred if adopted children show a positive correlation with their adoptive parents on a particular trait?

Answer 20

This provides strong evidence for environmental influences on the personality trait in question.

Question 21

How do family studies help in understanding the heritability of personality traits?

Answer 21

Family studies correlate the degree of genetic relatedness among family members with the degree of personality similarity, helping to determine if traits are heritable.

Question 22

What is the significance of studying twins reared apart in behavioral genetics?

Answer 22

Studying twins reared apart allows researchers to disentangle genetic influences from environmental influences since the twins share genes but not the same environment.

Question 23

Which personality traits have been most studied in behavioral genetic designs?

Answer 23

Extraversion and Neuroticism.

Question 24

What have studies found about the heritability of Extraversion and Neuroticism?

Answer 24

Studies have found that Extraversion and Neuroticism have significant heritability estimates, with Extraversion around 40% and Neuroticism around 30-50%.

Question 25

How do adoption studies contribute to our understanding of heritability?

Answer 25

Adoption studies help to differentiate between genetic and environmental influences by comparing adopted children to both their adoptive and biological parents.

Question 26

What role do shared and nonshared environmental influences play in shaping personality?

Answer 26

Shared environmental influences have little impact on personality variables, whereas nonshared environmental influences, such as unique experiences of individual children, play a significant role.

Question 27

What is genotype–environment interaction? Provide an example.

Answer 27

Genotype–environment interaction refers to the differential response of individuals with different genotypes to the same environments. For example, children with low MAOA activity are more likely to develop antisocial behavior

Question 28

What are passive, reactive, and active genotype–environment correlations?

Answer 28

• Passive genotype–environment correlation: parents provide both genes and environment to children without the children’s active role.
• Reactive genotype–environment correlation: parents respond to children differently based on the children’s genotypes.
• Active genotype–environment correlation: individuals with certain genotypes create or seek out particular environments.

Question 29

What is the DRD4 gene, and what personality trait is it most associated with?

Answer 29

The DRD4 gene is located on chromosome 11 and is associated with novelty seeking, which involves a tendency to seek out new and potentially risky experiences.

Question 30

What controversy exists around genetic research on intelligence?

Answer 30

The controversy centers on concerns that genetic findings may be misused to label individuals as superior or inferior, and may lead to preferential treatment in education or jobs, as well as arguments that standard intelligence tests do not capture all facets of intelligence such as social and emotional intelligence