BIOA01H3 Study Guide - Comprehensive Midterm Guide: Advantageous, Genotype Frequency, Polyphyly

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Published on 5 Oct 2016
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BIOA01H3
MIDTERM EXAM
STUDY GUIDE
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9/24/16
Biology Notes
1.4 Evolution
-evolution: changes over time
-natural selection: when there is a variation that is heritable the variants best suited for growth and reproduction
will contribute to the next generation
-environmental variation: variation among individuals due to differences in the environment (e.x some apples on
tree have better sunlight)
-genetic variation: differences in genetic material transmitted from parents to offspring
-differences in DNA can lead to differences in RNA and proteins which affect molecular functions o cells and ulti-
mately physical differences
-genetic variation arises ultimately from mutations
-mutations —> random errors during DNA replication, environmental factors (UV radiation)
-harmful mutations die out after a few generations and mutations that are neither harmful nor beneficial can persist
for thousands of years and those that are beneficial gradually become incorporated into the genetic makeup of
species
-Darwin: “decsent with modification”
-evolution predicts a nested pattern of relatedness among species depicted as a tree
-evolution can be studied by means of experiments
-laboratory evolution experiments help us to understand how life works, allow biologists to develop beneficial
strains of microorganisms (that for e.g remove toxins from lakes) and show how pathogens develop resistance to
drugs that are designed to eliminate them
21.1 Genetic Variation
-phenotype: observable trait (human height or wing colour)
-two factors contribute too phenotype: an individual’s genotype (set of alleles), and the environment
-genetic variation can be explored directly in terms of differences at the DNA sequence level
-species: individuals that can exchange genetic material through interbreeding (share alleles through reproduction)
-gene pool: all the alleles present in all individual species
-population genetics: study of genetic variation in natural populations
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9/24/16
-populations: interbreeding groups of organisms of the same species living in the same geographical area
-sources of genetic variation: mutation and recombination followed by segregation of homologous chromosomes
-somatic( occurring in body’s tissues) mutations
-germline( occurring in the reproductive cells (can be passed on) mutations
-neutral mutations: little or no effect on the organism
-deleterious: harmful effects
-advantageous: beneficial effect (improve survival or reproduction)
-advantageous mutation can increase in frequency in population as they result in better ability to survive and re-
produce
21.2 Measuring Genetic Variation
To understand patterns of genetic variation, we require information about allele frequencies
-allele frequencies: rates of occurrence of alleles in population
-allele frequencies help to make inferences about evolutionary process from patterns of genetic variation
-the allele frequency is just the number of that specific alleles present divided by the total number of alleles
-when a population exhibits only one allele at a particular gene, we say that the population is fixed for that allele
-three ways to measure genotype and allele frequencies in populations: observable traits, gel electrophoresis, and
DNA sequencing
Early Population genetics related on observable traits and gel electrophoresis to measure variation
-it is difficult to make direct inferences from a phenotype to the underlying genotype because: many traits are en-
coded by a large number of genes and because the phenotype is a product of both the genotype and the environ-
ment
-to resolve this issue scientists only studied phenotypes encoded by one gene however this was very limiting (e.x
human blood groups had one gene)
-single-gene variation became easier to detect later on with gel electrophoresis: separating particles by charge and
size due to electric current and then using dye to see particles better
DNA sequencing is the gold standard for measuring genetic variation
-gel electrophoresis was limiting since researchers could only study enzymes as they needed to be able to stain
specifically for enzyme activity
-DNA sequencing provided an unambiguous method of detecting all genetic variation
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Document Summary

Natural selection: when there is a variation that is heritable the variants best suited for growth and reproduction will contribute to the next generation. Environmental variation: variation among individuals due to differences in the environment (e. x some apples on tree have better sunlight) Genetic variation: differences in genetic material transmitted from parents to offspring. Differences in dna can lead to differences in rna and proteins which affect molecular functions o cells and ulti- mately physical differences. Mutations > random errors during dna replication, environmental factors (uv radiation) Harmful mutations die out after a few generations and mutations that are neither harmful nor beneficial can persist for thousands of years and those that are beneficial gradually become incorporated into the genetic makeup of species. Evolution predicts a nested pattern of relatedness among species depicted as a tree. Phenotype: observable trait (human height or wing colour)

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