heredity

Question 1

Behavior Genetics

Answer 1

• Study of the influence or roles of heredity
(nature) and environment (nurture) on
development

Question 2

Heredity

Answer 2

passing on of traits to offspring

Question 3

Heritability

Answer 3

degree of genetic influence on

a given trait or characteristic

Question 4

FERTILIZATION

Answer 4

Sperm and Egg each carry 23 single
chromosomes (not pairs), formed through
process of MEIOSIS

At conception, single cell with 46 chromosomes,
or 23 pairs, is formed: Zygote, then mitosis

Question 5

Errors in genetics

Answer 5

– Errors in base pairs, changes in sequencing,

chromosomal damage or duplication

Question 6

Sex-linked traits

Answer 6

Traits that differ in rate of occurrence between
males and females because of dominant and
recessive alleles on X and Y chromosomes
– X chromosome is BIGGER than Y, and has more
genetic info
• Many alleles (traits) on X do not have a “sister” or
corresponding trait on Y
– Recessive Alleles: any recessive allele on X
chromosome in MALES will result in TRAIT
EXPRESSION, whereas, a FEMALE must inherit the
trait from BOTH MOTHER AND FATHER
• Color blindness
– Dominant Alleles: will always be expressed in
FEMALES (any X will do); MAY be expressed in
males

Question 7

The G x E Interaction

Answer 7

• The interaction between nature
and environment
• Epigenetics: the study of the
epigenome, and factors that
influence it
• Epigenome: chemical tags/info on
chromosomes

Question 8

Twin Studies

Answer 8

study characteristics of MZ
and DZ twins
– Monozygotic twins: identical twins
• Originally one fertilized egg, which divided at the
first stage of conception in order to form TWO
fetuses; DNA is 100% identical
– Dyzogotic twins: fraternal twins
• Originally TWO fertilized eggs that developed at
the same time; DNA is 50% identical –> REGULAR
SIBLINGS

Question 9

Concordance rates

Answer 9

percentage of twins sharing
a trait or disorder

Monozygotic twins: co-twin of a depressed
twin is 2 TIMES as likely to have depression as the
co-twin of a depressed DYZOGOTIC twin

Question 10

Other methods to study heritability

Answer 10

Adoption studies: examines how adopted
child resembles biological parents and
adoptive parents with regard to various
characteristics
– E.g. Blood relatives more likely to have
depression than adopted relatives
• Family history: study the occurrence of
traits in biological family members
– Shared environment vs Nonshared
environment

Question 11

Heritability of Bipolar Disorder

Answer 11

Genetic Influences:
– 8-9% of first-degree relatives of people
diagnosed with Bipolar Disorder will ultimately
have Bipolar Disorder (GP incidence= 1%)
– Twin Studies:
• MONOZYGOTIC TWINS: 60-62%
Concordance rate
• DYZOGOTIC TWINS: 8-12% Concordance
rate
– Research suggests that 80% of variance is
genetic

Question 12

Temperament

Answer 12

Inherited personality traits
present in early childhood

Twin studies and adoption studies provide
support for heritability of temperaments
– 40 to 50% of variance

Question 13

Activity level

Answer 13

overall output of energy or behavior
• Vigor: intensity of behavior
• Tempo: speed of behavior

Question 14

Sociability

Answer 14

tendency to be with people rather than

be alone

Question 15

Emotionality

Answer 15

tendency to become physiologically

aroused in stressful situations

Question 16

Nature vs. Nurture: The effects of

the environment

Answer 16

We often talk about concordance rates,
but what about DISCORDANCE rates?
– In genetic studies, the variance that is NOT
accounted for by genetic influences reflects
the influence of the environment
– There are many ways in which environment
can influence personality development
• E.g. peer influences, experience-seeking, rewards
patterns, etc.