lecture 22 - schizophrenia

Question 1

What is ALS? (Amyotrophic lateral sclerosis)

Answer 1

Is a degenerative disorder that attacks the spinal cord and cranial nerve motor neurons.

Question 2

What is ALS also known as?

Answer 2

Lou Gehrigs disease or motor neuron disease

Question 3

is ALS hereditary?

Answer 3

90% of cases are sporadic (unknown cause) and 10% are from parents.

Question 4

Any other causes of ALS?

Answer 4

simple gene mutations that can cause protein misfolding and aggregation.

Question 5

Symptoms of ALS

Answer 5

symptoms include:
1) spasticity (increases tension of muscles, causing stiff and awkward movements)
2) exaggerated stretch reflexes
3) progressive weakness and muscular atrophy
4)paralysis

Question 6

how often do people get AlS and what is the lifespan?

Answer 6

disease typically starts at age 50 with a 2-4 year life span.
3 in 100,00 people get it
stephan hawking was diagnosed in his early 20s and kept being told he would die every 2 years.

Question 7

FTD-ALS

Answer 7

ALS and FTD (frontotemporal dementia) are now considered to be part of a common disease spectrum called FTD-ALS because of genetic, clinical and pathological similarities.
seems like any protein can misfold especially with gene mutations.

Question 8

common but harmful gene variants

Answer 8

most disorders that are associated with old age have a strong genetic component to them and have common gene variants that are associated with higher risk of getting a particular late onset disorder

Question 9

what kind of genes that would be quickly eliminated?

Answer 9

Gene mutations that lower reproductive success tend to get
eliminated from the gene pool fairly quickly.
ex: having gene variants associated with having half as many offsprings = less people having the gene variant because this would generate less offsprings

Very harmful gene variants are typically eliminated within a few generations, so they tend to be extremely
rare and recent in origin.
Slightly bad gene variants are removed more slowly, so they tend to be more common and older – inherited from
great grandparents and older generations.

Question 10

gene fixation

Answer 10

Most genes in our genome have gone to fixation
(virtually 100% prevalence in the human population)
because they promoted survival and reproduction under
ancestral conditions better than other genes did

Question 11

neutral gene variants

Answer 11

Neutral gene variants produce variations in human nature that
are not associated with better or worse reproductive success
(like different personality traits).

Question 12

have neutral genes become harmful?

Answer 12

Many of these gene variants are associated with diseases that show
the classic hallmarks of gene-environment interactions (i.e., they are
heritable, but prevalence rates vary widely across cultures and recent
history, and there are straightforward environmental explanations for
the variability in disease prevalence)

Question 13

environmental risk factors associated with each the following disorders
were not present in ancestral environments:

Answer 13

1)late onset disorders, due to rapid increase in human life spans - living until 70-80 years was not common back then
2) obesity and diabetes, due to the abundance and low price of unnaturally tasty food
3)asthma, due to new types and unnaturally high levels of antigens and pollutants - never had so much pollution
4)addictions to highly purified synthetic drugs, such as heroin and meth
5)depression and anxiety – although the cause is unclear, prevalence rates have
changed rapidly in recent history and vary enormously between cultures.

Question 14

Are psychiatric illnesses (like schizophrenia and autism) heritable?

Answer 14

heritable (20 to 80% of the variance in who has a given mental
disorder is well explained by genetics)

Question 15

Are Psychiatric illnesses common?

Answer 15

common (the frequency of severe mental disorders is around 4%)

Question 16

do people with psychiatric illnesses have issues with reproducing?

Answer 16

yes. harmful to reproductive success (the fertility rate for people with
severe mental disorders is about half the national average)

Question 17

would gene mutations associated with mental illness be neutral or advantageous in ancestral environments?

Answer 17

Nope it’s s hard to imagine they were neutral in most environments, cultures and peoples.
Across evolutionary time, gene variants that are not neutral are either
selected out (and should be extremely rare) or have gone to fixation
(and everyone should have them).

Question 18

The prevalence of schizophrenia

Answer 18

~1% of the population, and this
has been fairly consistent across cultures and recent history.

Question 19

Genes associated with schizophrenia?

Answer 19

hundreds of relatively common gene variants each
individually confer a very small statistical increase in the risk of
developing schizophrenia. A 0.01% increase with any gene variant.

Question 20

One theory for the prevalence of these schizophrenia susceptibility genes
is that certain combinations of them may be advantageous for
reproductive success.? is this true?

Answer 20

If this were true, the siblings of schizophrenics who don’t have the
disease should have increased reproductive success on average,
because they would be more likely to have the good combination of
these schizophrenia genes in comparison to the general population.

siblings of schizophrenics seem to have the same reproductive
success as the general population.