Why is one allele dominant?
- melanocytes can make two kinds of melanin: redish yellow or black
- melanin is shipped out in melanosome organelles into skin cells and results
in pigmentation of skin
- MC1R is embedded in melanocyte protein. When turned on, increases level of
cyclic AMP in the cell. (commonly used messenger). PRODUCE ONLY BLACK
- ASP MC1R is turned off and inactivates cyclic AMP, produces
pheomelanosomes and red pigment.
- Recessive allele makes some red and some black melanosomes. Allele gets
turned on and off. Can produce protein some of the time but not often
- Black allele is always on, always high camp
Dominance arises from the EXPRESSION of those alleles. From their protein
In red pigment, cAMP levels are ALWAYS low. So what?
An allele isn’t dominant to everything all the time. It really only has meaning for a
particular pair of alleles and HOW their biochemistry interacts.
When dealing with evolution over time thinking must be expanded out of families
Genes in Populations
- mendelian genetics still completely applicable
- common dominant allele & red recessive allele
- If we have a large group of dominant and a rare group of recessive, what will