Transcript SR6e Chapter 3 - Flip Flop Ranch

CHAPTER 3
GENES, ENVIRONMENT
AND DEVELOPMENT
Learning Objective
 What
do evolution and species
heredity contribute to our
understanding of universal
patterns of development?
Species Heredity

Genetic endowment
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Examples in humans
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What species members have in common
Govern maturation and aging processes
Two eyes, sexually mature at ages 12-14
Evolved through natural selection
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Genes passed on which allow species to
adapt
Evolution
 Evolution:
Charles Darwin (1809-
1882)
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Specie characteristics change over
time
New species can evolve from earlier
ones
 Main
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–
arguments
There is genetic variation in a species
Natural selection
 Adaptive
genes passed on more frequently
Kettlewell’s Moths
 An
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–
interaction
Genetic variability (color of wings)
Adaptation to a specific environment
(country vs.city)
 Survival
–
Requires adaptation
 Adaptation
–
Genetic variability
Modern Evolutionary
Perspectives
 What
we do today was adaptive for
our ancestors
 Species heredity based on natural
selection
 Genetic make-up gradually changes
 New or modified species arise
 Cultural evolution based on learning
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–
Better ways of adapting learned
Shared through language
Learning Objectives
 What
are the basic workings of
individual heredity, including the
contributions of genes,
chromosomes, the zygote, and the
processes of mitosis and meiosis?
 Note the difference between
genotype and phenotype.
Individual Heredity – The
Genetic Code

Zygote: Union of sperm & ovum at
conception
–
Contains 23 pairs of chromosomes
 One
pair from each parent
 Each pair influences a characteristic

Chromosomes: thousands of genes
containing DNA
 Meiosis: process producing sperm, ova
 Mitosis: cell-division process creating all
other cells
–
Throughout life
The Human Genome
Project
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Massive genome analysis projects
999/1000 human base chemicals:
identical
1/1000 accounts for differences between
us
Humans/Chimps share 96% genetic
material
Gene variants evolved in recent centuries
–

Adaptations to food sources, diseases,etc.
Findings also useful to identify genes
associated with disease, drug treatments
Genetic Uniqueness and
Relatedness

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ID twins: zygote divides forms 2
individuals
64 trillion genetically unique babies per
any couple
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2 chromosomes in sperm or ovum
Males: XY, Females: XX
Parent/Child: 50% related genetically
Siblings: on average 50% related
genetically
Fraternal twins: 2 ova released, fertilized
by 2 sperm
Translation of the Genetic
Code
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Genotype: genetic makeup a person
inherits
Phenotype: expressed traits of the person
Genes: instructions for development
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Regulator genes turn gene pairs on/off at
different times
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Characteristics like eye color
Turned on for adolescent growth spurt
Turned off in adulthood
Always influenced by environmental
factors also
Learning Objectives
 How
are traits passed from
parents to offspring?
 What is an example of how a
child could inherit a trait through
each of the three mechanisms
described in the text?
Mechanisms of Inheritance
 Single
–
–
gene-pair inheritance
Dominant gene = dominant trait
Recessive genes
 Trait
expressed if paired with a similar
gene (Homozygous)
 Trait not expressed if paired with
dissimilar gene (Heterozygous)
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–
Recessive traits: homozygous
recessive
Dominant traits: hetero or homozygous
gene pair
Example: Sickle-Cell
Disease
 About
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9% affected in US
Homozygous recessive
 Heterozygous
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Can transmit gene to offspring
If both parents carriers: 25% chance
 Example
–
are “carriers”
of incomplete dominance
Offspring may have sickling episodes
Sex-Linked Inheritance
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Single genes located on sex
chromosomes
Actually X-linked
Males - no counterpart on Y chromosome
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Females - counterpart on 2nd X
chromosome
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Only needs one to be color-blind
Usually for normal color-vision (dominant)
Must inherit on both to be color-blind
Also Hemophilia, Duchene MS, others
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X-Linked Inheritance
Polygenic Inheritance
 For
most important human
characteristics
–
Height, intelligence, temperament, etc.
 Trait
influenced by multiple pairs of
genes
 These traits are normally distributed
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I.e., found in the same proportion in all
populations
Learning Objectives
 What
methods are used to screen
for genetic abnormalities?
 What are the advantages and
disadvantages of using such
techniques to test for prenatal
problems?
 What are some abnormalities that
can currently be detected with
genetic screening?
Mutations
 A change
in gene
structure/arrangement
 Produces a new phenotype
 More likely in sperm than in ova
 May be harmful or beneficial
 Can be inherited by offspring
Chromosomal
Abnormalities
 Errors
in chromosome division
during meiosis
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Too many or too few chromosomes
result
Most spontaneously aborted
 Down
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Syndrome: Trisomy 21
Physical characteristics
Mental retardation
Related to age of both parents
Often develop Alzheimer’s in middle
age
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The rate of Down
syndrome births
increases steeply
as the mother’s
age increases.
Sex chromosome
Abnormalities
 Turner’s
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syndrome: 1/3000 females
Single X chromosome: small, unable to
reproduce
 Klinefelter
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syndrome: 1/200 males
XXY: Sterility, feminine traits
 Fragile
X syndrome: one arm on X is
fragile
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Usually males (sex-linked inheritance)
Most common heredity cause of MR
Genetic Diagnosis and
Counseling
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Helps people understand and adapt
Prenatal diagnosis: techniques include
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Amniocentisis, preimplantation genetic
diagnosis
Human genome project yielded much info
Eg., Huntington’s disease
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Deterioration of nervous system
Single dominant gene
One affected parent = 50% chance in
offspring
Learning Objectives
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How do scientists study the contributions
of heredity and environment to behavioral
characteristics?
Describe the logic of the methods, as well
as strengths and weaknesses of each
method
How can concordance rates help
researchers estimate the influences of
heredity and environment?
How do genes, shared environment, and
nonshared environment contribute to
individual differences in traits?
Behavioral Genetics
 Genetic/environmental
cause of
traits
 Heritibility estimates
 Experimental and selective breeding
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Tryon’s maze-bright rats
 Twin,
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adoption, family studies
Reared together or apart
Concordance rates
Estimating Influences
 Genetic
similarity
– Degree
 Shared
– Living
of trait similarity
environmental influence
in the same home
 Non-shared
environmental
influences
– Unique
experiences
Molecular Genetics
 Analysis
–
of genes and their effects
May compare humans with other
animals
 Eg. Alzheimer’s
disease
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Most common form of old age
dementia
– Twin studies show heritability
– Possible genetic links being tested
– Environmental factors also being tested
 High
cholesterol, head injury
Learning Objectives
 How
do genes and environments
contribute to individual differences in
intellectual abilities, personality and
temperament, and psychological
disorders?
 What do researchers mean when
they talk about the heritibility of
traits?
 Which traits are more strongly
heritable than others?
IQ: Accounting for
Individual Differences
 Correlations
highest in identical
twins
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Genetic factors determine trait
 Correlations
higher if twins reared
together
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Environmental factors
Non-shared experiences influential
 Identical
twins more alike with age
Temperament &
Personality
 Temperament
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Identical twins = .50 to .60
Fraternal twins = 0 (even reared
together!)
 Personality
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Correlations
Correlations Similar
Shared environment unimportant
Genetic inheritance important
Non-shared experiences important for
differences
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Correlation
between
the traits of
identical
twins
raised
apart in
Minnesota
Twin Study.
Psychological Disorders
 Schizophrenia
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ID twins: 48%
Fraternal twins: 17%
Affected parent increases risk even if
adopted at birth
 Inherited
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concordance rates
predisposition
Environmental factors (triggers)
Prenatal exposure to infection
suspected
Learning Objectives
 What
is an example that illustrates
the concept of a gene-environment
interaction?
 What are three ways that genes and
environments correlate to influence
behavior?
 What are the major controversies
surrounding genetic research?
Gene-Environment
Interactions
 Based
on correlations
 Eg., Sociable genes
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Passive interaction
 Create
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Evocative interaction
 Smiley
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social home environment
baby gets more social stimulation
Active interaction
 Shy
child seeks solitary activities