BIOL 122 Lecture Notes - Lecture 9: Santa Barbara City College, Genetic Drift, Genetic Variation
Document Summary
Nitrogenous bases (a,t,c, or g) long strands of dna are wound into chromosomes. Genes: regions of dna that code for functional proteins. Alleles: different forms of a particular gene. Polygenic: when a single trait is affected by several genes, i. e. body size. Show a lot of variation in a population traits assume a bell curve . Pleiotropy: when a single gene affects multiple traits. Epistasis: when the expression of one gene can be controlled by other genes, i. e. feather structure in chickens hair color, eye color. Organisms inherit one form of a gene from mom and the other from dad. If the 2 alleles are different: heterozygous. If the 2 alleles are the same: homozygous. Dominant alleles: mask the expression of other alleles. Recessive alleles: expression masked by other alleles. Unless 2 recessive alleles are inherited together. Mutation: random changes in the dna code. Mutation rates vary from species to species.