Behavior Genetics

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Dec 14, 2012 (4 years and 7 months ago)

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Behavior Genetics

Chromosomes, Genes, & You


23 pairs of rod
-
like structures within nuclei
of cells


Genes, composed of DNA


DNA is template for production of RNA


RNA produces proteins from amino acids


You are a collection of proteins


Human Chromosomes


Genes and Environment


Need both genes and environment for life


Different environments


different
developments


Different genes


different developments


Gene x Environment Interaction


effect of gene depends on type of
environment


effect of environment depends on genes


Mitosis and Meiosis


Mitosis


exact duplication of DNA


Meiosis


production of eggs and sperm


Crossing Over


exchange of material
between paired chromosomes


Each gamete
gets
only one chromosome
from each pair


Random Assortment of chromosomes


No two gametes likely identical



Sexual Reproduction


Produces genetic diversity in offspring


Good strategy for dealing with a changing
environment


In steady environment asexual
reproduction is better strategy.


Hydras change back and forth between
sexual and asexual


Some species
lost the ability to reproduce
asexually

Hydra in Pond Water


Defining Sex


Female = makes few but large gametes


Male = makes many but small gametes


Chromosomal
sex:


Humans: XX
= female, XY =
male


Birds: ZZ = male, ZW = female


Some Insects: XX = female, X0 = male


Hormonal sex


Genital sex


Gender identity



Simple Inheritance


Locus
--

location of gene on chromosome


Alleles
--

different forms of genes that can
be found at a locus.


Homozygous
--

same allele on both
chromosomes


Heterozygous
--

different alleles


Phenotype


observable characteristics


Genotype


genetic composition

A/B/O Blood Types


The A gene codes for protein A


The B gene codes for protein B


The O gene codes for no protein


A and B are dominant over O.


AA or AO


blood type A


BB or BO


blood type B


AB


both proteins produced (codominance)


OO


blood type O

Genetic Context


Action of a gene depends on other genes


May be dominant in one genetic context,
recessive in another.


Gene as a funnel in a series.


The smallest funnel limits the rate of flow
and determines the outcome.


Rate Limiting Step


Red/White Snapdragons


The red/white gene controls a rate
-
limiting step.


Homozygous white


very little of the enzyme
associated with red coloration is present.


Heterozygous


medium amount of enzyme,
pink flowers.


Homozygous Red


lots of the enzyme, red
flowers.


Codominance


both genes affect flower color.


Purple/White
Pea Flowers


Is a threshold amount of chemical necessary to
make flowers
purple.


At rate limiting step one allele allows for
production of not enough for
purple.


Other allele (dominant) allows for enough to
make flowers purple.


If have one or two of the dominant genes,
flowers are purple.


Dominance


the recessive genes
have
an effect
only in the
homozygous
condition.


The Basenji is fearful of strangers.




The cocker spaniel is not.


What About A Cockenji?


Inheritance of Fearfulness


John Paul Scott and John Fuller


Basenji x Basenji


fearful pups


Cocker x Cocker


fearless pups


Basenji x Cocker


fearful pups


Dominant F gene codes for Fearfulness


Recessive f gene codes for fearlessness


F
1

dogs are heterozygous, Ff


Breed F
1

Dogs With Each Other

Mother

Father

F

f

F

FF

Ff

f

fF

ff

Backcross F
1

Dogs With Cockers

F
1

Cocker

F

f

f

fF

ff

f

fF

ff

Backcross F
1

Dogs With Basenji

F
1

Basenji

F

f

F

FF

Ff

F

FF

Ff

Nature & Nurture: Heritability


Nature = Effect of genes


Nurture = Effect of environment/learning


What % of differences among individuals
in a population are due to genetic
differences among the individuals.


Inbred mice: 0%


Outbred mice in controlled environment:
100%

Behaviorists’ Delusion


If a trait can be modified by environmental
change or learning, it must have been
established by environmental factors.


PKU


genetically caused inability to
metabolize properly certain foods.


Detected by testing babies’ blood.


Treated environmentally


avoid certain
foods.

Habitat Selection


Genes


Habitat Selection


Behavioral
Development


Two subspecies of
Peromyscus
maniculatus


One normally lives in the forest.


The other in the prairie.


What causes behavioral differences
between the subspecies, genes or
environment?

The Deer Mouse


Wecker, 1964, Scientific American


Gave field
-
caught mice choice of habitat.


They chose the one typical of their
subspecies.


Gave lab
-
born mice choice of habitat.


Ditto. Their genes determined their
choice


If the habitat affects a behavioral trait, is
that due to environment (proximal) or
genes (ultimately)?



Parenting Styles and Offspring
Competence


Observed correlation between parenting
style and competence of child.


Parental style


child’s competence ?


Different babies evoke different parental
responses.


Child’s genes


child’s competence


parental style ?



Child’s genes


child’s behavior


parental style


child’s competence ?

Inheritance of Polygenic
Characteristics


Tryon, 1940


Maze intelligence of rats.


Breed brightest with brightest, dullest with
dullest.


Six generations


two new strains of rats.


Cross
-
Fostering to control for effect of
parental style.

Cross
-
Fostering and Maze
Intelligence

Biological Mother

Foster
Mother

Bright

Dull

Bright

25

15

Dull

20

10

Inheritance in Humans


Can’t do selective breeding experiments


Can correlate genetic similarity with
psychological similarity


Of those genes on which humans differ,
what percentage do you share with your


monozygotic twin


100%


dizygotic twin, sibling, parent


50%


half
-
sib, grandparent, aunt, uncle


25%


cousin, great grandparent


12.5%


Monozygotic Twins


Obtain many pairs of
monozygotic twins.


Measure each twin on
some characteristic,
such as intelligence.


Compute Pearson
r
.


Here
r

= .85

Pair

a

b

c

d

e

f

one

1

3

6

7

8

9

other

3

4

4

5

8

7

Nontwin Siblings


Obtain many pairs of
nontwin siblings.


Measure each sib.


Compute Pearson
r


Here
r

= .47


Do same with aunts,
cousins, etc.


r

decreases as does
genetic similarity


Pair

a

b

c

d

e

f

one

1

3

6

7

8

9

other

5

1

4

9

5

6

Genetic and Psychological
Similarity


Data like these can be use to estimate
heritability.


Extroversion


Neuroticism


Dominance and aggressiveness


Intelligence


Even political conservativism.

If Your Mother Took Home the
Wrong Baby


Would that baby have grown up to be just
like you are now? (Do genes matter?)


Would you, raised by other parents, have
turned out the same? (Does environment
matter?)

Reluctance to Accept Behavior
Genetics


Accept that genes affect physical
characteristics, but


Resist idea that they affect mental and
behavioral characteristics.


The delusion of free
will.


We did not chose our genes.


If they determine our behavior, our will is
not free.



Genes


Nervous System


The brain and nervous system is a
physical characteristic.


Genes affect its development.


Our mental states and behavior are under
the control of the brain and nervous
system.


Thus, genes affect our mental life and
behavior.

If Your Mom Took a Puppy Home
From the Hospital


Instead of you


And raised it as her child.


Would that dog be just like you are now?


Of course not.


Genes explain differences between
species.


Why not differences between individuals of
same species?

Egalitarianism


All persons should have equal political and
social rights.


Do all have to be equal to have equal
rights?


If so, behavior genetics is a threat to
egalitarianism.


I think not. We should celebrate our
diversity, not deny it.



Racism and Behavior Genetics


Immigration policy, IQ, and national origin


Other racist BS (Bad Science)


No good evidence that genes related to
skin color are directly related to
psychological attributes.






Correlates of Skin Color


Skin color can be indirectly related to
psychological attributes in a racist society.


Imagine
Blue People

subject to racial
discrimination.


Not given same economic & social rights.


Such racism would cause Blue People to
differ psychologically from others.


The Blue Fugates


Blue Hemoglobin


Methemoglobin


Diaphorase normally converts to red.


Recessive condition = no diaphorase


Inbreeding in remote locations


Treatment with methylene blue.

Martin Fugate


A blue Frenchman.


1820, Troublesome Creek, Eastern KY.


Wife carried the recessive gene.


Four of their seven children were blue.


The blue clan spread in isolated
community.


Later, coal mining and railroads brought
new people, outbreeding.


Benjamin Stacy


Very blue at birth, rushed to hospital in
Lexington.


Discovered he descended from Martin
Fugate.


Is now relatively normal in color.


Lips and nails turn blue when cold or
angry.

Genetic Engineering


1985, Monsanto Company


Human gene transferred in petunia plants


Human chorionic gonadotropin.


Medically used to induce ovulation


& to stimulate production of testosterone.


Gene was passed on to next generation of
petunias.

Firefly Tobacco


1986, UC San Diego


Gene from firefly transferred to tobacco.


Produce enzyme luciferase.


Plant glows in the dark.


Also transferred to monkey cells.

Firefly Tuberculosis


1993, Albert Einstein College of Medicine.


Firefly genes into TB bacteria.


If healthy, the bacteria glow.


If an antibiotic weakens them, stop
glowing.


Allows more rapid identification of effective
antibiotic for new strains of TB.

Jellyfish Glow Pigs


Genetic Testing


Do you have genes that lead to disease?


Identify them, treat the disease now.


Don’t let your employer know.


Don’t let your insurer know.


California HMO


Fetus has gene for cystic fibrosis


Will pay for abortion


Will not pay to care for child if born.

Check Chromosomes in Sperm


Infertility maybe due to bad sperms?


Check the sperms’ chromosomes.


Can’t do it until has fertilized an egg.


Ethical problems using a human egg.


Practical problems using a human egg.


So use a hamster egg.


Ryuzo Yanagimachi, 1970’s, Univ. Hawaii

From Ryuzo’s Lab

Jellyfish Glow Mice