Research the Literature on your Own

1. There is at least one visual task that dichromats perform better than trichromats.  Read the paper listed below and discuss this experiment and its evolutionary implications.
   
   Morgan MJ, Adam, A, Mollon JD (1992) Dichromats detect colour-camouflaged objects that are not detected by trichromats.  Proceedings of the Royal Society (London) Series B (Biological Science) 248: 291-295.
   
   
2. On the web site of the National Center for Biotechnology Information at the National Institutes of Health (NIH), one can find the amino acid sequence files for rhodopsin and the cone pigments from various species, including humans.  In the collection of protein sequences (click on “Protein”) the accession numbers for these sequences are: human rhodopsin (NP_000530), human S pigment (NP_001699), human M pigment (NP_000504), human L pigment (NP_064445).  Use the “BLAST” program on this web site to search the database with each of the human rod and cone pigment sequences to see how closely they resemble each other and the sequences of visual pigments from other species.
   
   
3. There are many examples of related proteins encoded by gene families that have expanded by duplication and sequence divergence.  Examples include the adult, fetal, and embryonic hemoglobins, and the more distantly related myoglobin and neuroglobin proteins.  In what ways do the divergent globin sequences contribute to their specialized functions?