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Unformatted text preview: BILD 3 – Organismic and Evolutionary Biology Lecture 2 Definition of Microevolution- Microevolution is: o A change in the genetic composition(allele frequency ) of a population over time(across generations) o Evolution within species- Population : Group of individuals from the same species that live in the same area and have the potential to mate- Allele : A specific variant of a gene. Different individuals of a species have the same genes, but may have different alleles o Evolution occurs if the prevalence of that allele changes 4. Steps of Microevolution 1. Variation in a trait exists within populations o Example: There are TWO KINDS of peppered moths: black and white o Evolution requires variation The ultimate source of variation is mutation A mutation alters a DNA sequence, thus creating a new allele Mutations maybe deleterious (bad), favorable (good), or neutral with regard to their effect on fitness(reproductive success) Types of mutations: • Point Mutations o A point mutation is a change in one nucleotide in a gene which happens during DNA replication Can lead to the production of an altered protein o Types of point mutations: Silent : Doesn't alter the amino acid that's produced(as if there's no mutation AT ALL) Nonsense : Stops production of the amino acid Missense : Produces a different amino acid • Conservative: Same functional group • Non-conservative: Different functional group Order of impact(least to greatest): Silent --> Conservative --> Non-conservative --> Nonsense • Insertion and Deletions (of nucleotides) o RNA is translated by the codon –sets of 3 nucleotides Amino acid will still be read correctly after insertion and deletion, less impact on fitness o Not inserting/deleting nucleotides in multiples of 3 produces frameshift mutations • Macromutations 1. Chromosome Inversion Chromosome breaks, centerpiece flips around, and reattaches Inversions are inherited as " supergenes " 2. Gene duplication Important when an individual only needs one functional gene, but the copy of this functional gene is duplicated and is free to mutate(individual can still perform that function with the original functional gene) until another functional gene is produced(new function) 3. Polyploidy Error of mutation during meiosis 2. Variation in traits is inheritable o Example: Black moth + Black moth --> Black moth, White moth + white moth --> white moth o Phenotype – The characteristics of an organism, due to both genes and the environment o Genotype – Genetic composition of an organism o Environment + Genotype = Phenotype o Heritability Definition: Proportion of variation in a trait that has a genetic basis Heritability = Genetic variation/Phenotypic variation...
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This note was uploaded on 09/03/2011 for the course BILD 3 taught by Professor Wills during the Summer '07 term at UCSD.
- Summer '07