Transcript what do you think is the inheritance pattern?

Lesson 14: Heritability
• learn about the methods for studying traits to
determine if genes influence them;
• specifically learn about how to analyze data
from twin studies; and
• understand the genes that influence alcoholism
specifically and addiction generally.
Genes controlling drug use?!?!?Activity 1
Separated at birth, the JIMS.
What did you think about that?
How would you study the role of genes?
How would you determine if a trait was
inherited?Activity 2
1. Does the trait run in
families?
3. With non-humans:
Selective Breeding
2. Do individuals with genetic
identity share the trait more than
those without?
Question:
• Members of a local “Alcoholics Anonymous”
meeting got to talking about their parents.
They couldn’t help but notice that a very
large number of them had an alcoholic
parent. In what way is this inadequate
evidence that alcohol addiction is genetically
controlled?
How to map families: Displaying
Phenotypes
Pedigree Analysis: shaded = ?
displays trait (may or
may not be genetic)
What do you think could be the
Mendalian genotypes?
Dominant vs. Recessive
Can this work?
aa
aa
A_
A_
aa
aa
A_
A_
aa
A_
aa
A_
Displaying Phenotypes-try this one
Hatched symbol –
intermediate phenotype
(incomplete dominanace)
Aa
What is wrong with this
pedigree?
What do we need to change
to make this work?
Aa
A REAL pedigree: what do you think is
the inheritance pattern?
??
aa twins Autosomal
dominant
A REAL pedigree: what do you think the
inheritance pattern is?
If we call the gene for the trait on the
previous pedigree “A”, what is the red
circled woman’s genotype?
1.
2.
3.
4.
5.
6.
Affected
Unaffected
AA
Aa
aa
Insufficient information
Could this trait (filled in
symbol is a heroin addict) be
controlled entirely by genes?
1.
2.
3.
4.
Sure
No way – addiction is not
genetic
No way – phenotypes are
not consistent with
expectations
Not enough information
How alike are twins?Activity 3
Relationship Parent –
child
Genetic
50%
similarity
Sibling
Fraternal
(non twin) twins
25%
25%
Identical
twins
99.99%
What do twins look like in pedigrees?
What is the difference between concordant
and discordant in twins?
• Are fraternal twins more likely to be
concordant or discordant for a trait?
• What about identical twins?
• Does it matter if they are raised apart or
together?
 If high concordance among identical twins,
raised apart, trait can be said to be VERY
influenced by GENETICS
Likelihood of
becoming an
alcoholic
How do these studies tell us about genetic
influence of alcoholism? Activity 5
25
IT concordance
76%
36%
5
FT concordance
61%
25%
A trait that is, at least partially, genetic will
show which of these relationships?
1. Higher concordance values for males than females
2. Higher concordance values for identical twins than
fraternal twins
3. Higher concordance values for twins reared together
than twins reared apart
4. Higher concordance values for mother-son than
father-daughter
Can one have an addictive personality?Activity6
• Discuss with your table group: cite evidence
from the following presentations:
• Bar Flies: alcoholism in fruit flies
• Alcoholism genes
• How do genes impact addiction
• Other factors
So, is there an alcoholic gene?
Genes that encode response proteins:Activity 4
• What type of genes should we consider when
talking about drugs?
• Genes that encode receptors (for drugs or NT)
• Genes that encode enzymes (for drugs or NT)
• Genes that encode recycling transponders (for
NT)
How does genetics relate to alcoholism?
Started with SNP analysis
Poor dopamine
binding – crave more
opportunities for
dopamine release
D2DR
ALDH

GABA receptors
Serotonin transporters
Good aldehyde metabolism, fewer side
effects, happy to continue to drink
Less GABA binding – less you notice
alcohol’s effects
Great serotonin recycling, more you turn
to alcohol to self-medicate poor mood
Even with all this genetic info, does this
mean one WILL be an alcoholic?
From this pedigree for the trait
(abuse of heroin), we can
conclude that:
1.
2.
3.
4.
5.
Heroin abuse is common
Heroin abuse is dominant
Heroin abuse is recessive
Heroin abuse is genetically controlled
We can’t conclude that genes totally
control heroin abuse at all
Candidate Gene Approach: How can genes
affect behavior? Activity 7
• How do your genetics affect your response to
nicotine?
Which of the following best describes
reward deficiency syndrome?Activity 8 READ NOW
1. There is too little dopamine produced by the
brain
2. The dopamine is recycled too fast to give
pleasure
3. There are less than normal numbers of the
D2DR receptors
4. Glutamate is released instead of dopamine
5. GABA inactivates the dopamine
What are pharmacogenetics?
• Discuss your findings from Activity 9
• Why might it be beneficial – how will it change
medicine?
Aside from genes, discuss some of the risk
and protective factors that can influence
addiction: Activity 10
What were your findings from the Healthy
Youth Survey results?