BIOL 1111 Lecture Notes - Lecture 2: Silent Mutation, Allele Frequency, Population Bottleneck
13 Jun 2018
School
Department
Course
Professor
Agents of Microevolution
1. Mutations
-spontaneous heritable change in DNA
-rare event, significant over long time
-major source of heritable variation
Deleterious mutations: harmful change
Lethal mutations: cause death; may persist if recessive trait is hidden
Neutral mutations: neither harmful nor helpful
-Silet utatios do’t alter AA, ut eve AA hage ay ot alter protei futio
Advantageous mutation: beneficial change
-natural selection may favour this mutation
**Almost all gene loci have genetic variation but many are not observable
2. Gene Flow
-movement of alleles across different populations
-may occur from individuals or gametes
-life history, behaviour, migration may enhance gene flow
-dispersal agents enhance gene flow (ex. Animals spread seeds through digestion, wind dispersion,
water current, ect.)
3. Genetic Drift
-random unpredictable changes in allele frequencies
-most important in smaller populations (can lose characteristics altogether)
-reduces genetic variability
Population bottleneck: reduction in alleles due to population reduction (ex. Hurricane, wildfire,
overexploitation of species)
Founder effect: due to few individuals starting new population
4. Natural Selection
-increase in traits that enhance survival and reproduction from one generation to the next
-selected for and accumulate in a population
-if a phenotype is successful, all alleles in the organism is selected
-even though a particular phenotype may help you in survival, you are also passing on alleles that may
not be selected for (due to them being on the same chromosome), which may not be beneficial
Relative Fitness: a measure of reproductive success
-number of successful offspring compared to others in population
-allele frequency increases if individuals carrying it have more offspring than others
-relative reproduction success is natural selection
5. Nonrandom Mating
-occurs when individuals select mates with similar
phenotype/genotypes
Inbreeding
-individuals select genetically related mates
-self-fertilization in many plants and some animals
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Lethal mutations: cause death; may persist if recessive trait is hidden. **almost all gene loci have genetic variation but many are not observable. Sile(cid:374)t (cid:373)utatio(cid:374)s do(cid:374) t alter aa, (cid:271)ut eve(cid:374) aa (cid:272)ha(cid:374)ge (cid:373)ay (cid:374)ot alter protei(cid:374) fu(cid:374)(cid:272)tio(cid:374: gene flow. Life history, behaviour, migration may enhance gene flow. Animals spread seeds through digestion, wind dispersion, water current, ect. : genetic drift. Most important in smaller populations (can lose characteristics altogether) Population bottleneck: reduction in alleles due to population reduction (ex. Founder effect: due to few individuals starting new population: natural selection. Increase in traits that enhance survival and reproduction from one generation to the next. If a phenotype is successful, all alleles in the organism is selected. Even though a particular phenotype may help you in survival, you are also passing on alleles that may not be selected for (due to them being on the same chromosome), which may not be beneficial. Number of successful offspring compared to others in population.
