Steven Crane Compiled Section Handouts. Human Behavioral Biology 2012

Alternative splicing. Can rearrange the exons and selectively keep some of them for translation into protein.

That's how we can have 20,000 genes but also have 100,000 different proteins.

3. This means any given exon may end up in many proteins. Mutate that one exon and you can amplify that mutation to affect many proteins (overlapping genes).

How did the prairie vole example show these principles?

1. 
   A mutation in the promoter for vasopressin receptors changed where the repressors were.
   

2. In monogamous voles the vasopressin receptors are expressed on dopamine neurons.

3. In polygamous voles the vasopressin receptors are NOT expressed on those dopamine neurons. So when these voles mate and vasopressin is released, the polygamous ones aren't reinforced to be monogamous in the same way the monogamous ones are.

4. This emphasizes that it's not the protein (the vasopressin receptor) itself that's changed, but rather the context in which that gene is expressed.

Three (simplistic) examples of novel if-then clauses that you could explain with the above mechanisms.

1. 
   If it's dry out, then retain water --> if it's dry out, then mate. (seasonal mating).
   
2. 
   If you smell a relative, then nurse them --> if you smell a relative, don't mate with them. (incest avoidance).
   
3. 
   (or you change the if part): if you are secreting glucocorticoids, then suppress immunity --> if you are secreting progesterone, then suppress immunity. (maternal immunosuppression during pregnancy).
   

How does the existence of duplicated genes/copy number variants give us more explanatory wiggle room when we're looking at genetics and behavior?

1. 
   So you can have duplications of an entire gene.
   
   1. 
      One can get knocked out or mutated into oblivion and you're still okay
      
   2. 
      You can also use these duplicates to double the amount of protein you produce given the same promoter activation.
      
   3. 
      So one can mutate a bit and the other can serve as a backup.
      
2. 
   Examples:
   
   1. 
      You see a lot of copy number variants in the genomes of those with schizophrenia
      
   2. 
      Steroid hormone receptors
      

Who wins in the end? The gradualist creeps or the PE jerks?

1. 
   Both! Yay.
   
2. 
   Gradualism:
   
   1. 
      Molecular evidence: small point mutations CAN produce slight changes in protein function that can be selected for.
      
   2. 
      SOME fossil records show evidence for gradualism
      
3. 
   PE's evidence is all laid out above. Also:
   
   1. 
      We've seen punctuated events in our lifetime. Four examples
      
      1. 
         Siberian foxes that look like dogs
         
      2. 
         Chicago rat skins show rapid change since 1850
         
      3. 
         Human populations exposed to western diets undergo almost a bottleneck of diabetes
         
      4. 
         Bacteria evolving antibiotic resistance
         
4. 
   And they can both happen simultaneously in different realms.
   

Example exam questions