BIO152H5 Lecture Notes - Lecture 16: Phylogenetic Tree, Macroevolution, Species Problem
Document Summary
After graduation, you and 19 of your closest friends (lets say 10 males and 10 females) charter a plane to go on a round-the-world tour. Unfortunately, you all crash land (safely) on a deserted island. No one nds you and you start a new population totally isolated from the rest of the world. Two of your friends carry (i. e. are heterozygous for) the recessive cystic brosis allele (c). In a small island population, 48% of the inhabitants are carriers for cystic fibrosis. Diploidy maintains genetic variation in the form of recessive alleles hidden from selection in heterozygotes. Balancing selection occurs when natural selection maintains stable frequencies of two or more phenotypic forms in a population. Heterozygote advantage occurs when heterozygotes have a higher fitness than do both homozygotes. Natural selection will tend to maintain two or more alleles at that locus. Heterozygote advantage can result from stabilizing or directional selection.
