A relatively small number of genes appear to account for much of the variation in skin color observed in humans. Two genes that have undergone positive selection in northern latitudes are OCA2 in Asian populations and SLC24A5 in European populations. In the ancestral African population, the SLC24A5 gene produces a protein with an alanine at amino acid position 111. In the European population the amino acid at position 111 is threonine. The protein that is produced from the SLC24A5 gene exchanges an ion of Na+ from the cell cytoplasm for a Ca2+ ion on the outside of the cell. This exchange appears to be necessary for normal melanin synthesis. In East Asian populations, the OCA2 gene produces a protein with the amino acid arginine at position 618 whereas the ancestral amino acid at that position is histidine. For both genes, the mutation arises from a single base change called a Single Nucleotide Polymorphism The mutations in the SLC24A5 gene affects protein expression in ___________________ while the pigments produced and secreted from these cells are taken up by __________________.

Binding of a hormone to the receptor depicted in the accompanying figure would cause the receptor to bind __________ near its carboxy terminus.  

Covalent bonds are formed between amino and carboxy groups in proteins by:

The mushroom Amanita phalloides contains a peptide called alpha-amanitin. This toxin blocks Pol II which catalyzes phosphodiester bond formation between ribose sugars in mRNA. The initial effect of the toxin is to block:

Epidermolysis bullosa is an inherited disease where keratinocytes separate from the dermis. You would expect that the mutations which cause this disease to be genes that encode for proteins found in:

Hydrogen bonding between the carbonyl oxygen of one amino acid and the hydrogen on the amine of a nearby amino acid in an i + 4 arrangement is responsible for the _______ structure in proteins.

Two solutions are separated by a membrane that contains only channels permeable to water (aquaporins). The solution in the left-hand compartment contains 50 millimolar NaCl, which dissociates completely, and the right hand compartment contains 100 millimolar urea which is a small, charged molecule that does not dissociate.  Which of the following statements is correct?

(9 points) Peptides hormones are synthesized on endoplasmic reticulum and packaged in before being attached through the motor protein to a cytoskeletal protein polymer called the for transport to the axon terminal. This motor protein converts chemical to mechanical energy by cleaving to . Because the peptides are propelled toward the axon terminal, this protein is said to be a end directed motor. Growth factors moving in vesicles in the opposite direction are propelled by the end directed motor, .

What happens if you cheat on any assigned activities?

Disinfectants used on exam room surfaces may include which of the following?