Evolution Vocabulary Genetic Variation

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Quantitative Traits

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traits that exhibit continuous variation rather than discrete character states

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Variance

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Genetic variance plus the environment

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Heritability

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amount of genetic variance divided by the total variance (genetic plus environmental)

1 is totally genetic

0 is no genetic relationshipo

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Synonymous mutation

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those that do not change amino acid

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Nonsynonymous mutation

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those that DO change an amino acid

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Pleiotropic mutations

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mutation that impacts many characters

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Phenotypic plasticity

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change in phenotype caused by environment not genetics

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Norm of reaction

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the variety of different phenotypes that can be produced by a single genotype under different environmental conditions

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Cultural inheritance

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Behavioral traits that are learned from adult individuals

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Maternal Effect

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variation that is not genetic but due to factors such as maternal care or yolk composition

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Epigenetic inheritance

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Phenotypic differences that are transmitted among generations of cells but are not based on DNA sequence differences

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Allele frequency

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promotion of a population carrying a specific allele

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Genotype frequency

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the proportion of a population with a specific genotype

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Hardy-Weinberg Principle

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Determine genotype frequency in a population

-random mating, no mutation, no gene flow, infinite population size, equal probability of survival

1=p^2+2pq+q^2

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Inbreeding

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when individuals are more likely to mate with relatives than non-relatives

common in organisms that can self fertilize or in small pops

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Inbreeding coefficient (F)

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probability that an allele is identical by descent

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Lethal aleles

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lead to death when homozygous. usually recessive at very low frequency

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Inbreeding depression

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when mating among related individuals causes a decline in fitness and survival

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Linkage

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occurs when genes/loci are in close physical proximity on chromosome so they are usually together

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Linkage disequilibrium

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occurs when loci are commonly associated due to physical linkage or other mechanisms

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Polygenic traits

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controlled by multiple genes

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Artificial selection

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when a particular trait is manually selected for i.e. dogs

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Cline

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gradual change in a character or allele frequency over a geographic distance

i.e. body size increase with increasing latitude in deer

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Ecotype

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a habitat-associated phenotype

-Can have both environmental and genetic components

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Central Dogma

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DNA-> RNA-> Protein

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Gene

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region of DNA that is transcribed to mRNA

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Control region

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untranslated regions where enhancers and repressors bind to regulate translation

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Exons

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translated region of the gene

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Introns

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sections that are transcribed but not translated

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Alternative splicing

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when exons are removed from the final mRNA that will be translated

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Gene Families

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groups of genes that are similar in sequence and function i.e. human hemoglobin

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Mutation

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process of alteration of a sequence of DNA

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Haplotype

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distinct genetic sequence that is different from other sequences due to mutation

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Point Mutation

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Change in single base pair

-transition- purine to purine or pyrimidine to pyrimidine

-transversion- purine to pyrimidine or vice versa

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Framshift mutation

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mutation that adds or delete one or more nucleotides to a sequence, changing the downstream codons

Indel-insertion/deletion. Unclear if nucleotides have been added or removed

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Independent assortment

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when non homologous chromosomes pairs align and separate randomly

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Crossing over

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when non-sister chromatids of a homologous pair exchange pieces

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Intragenic recombination

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when recombination occurs within gene

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Unequal crossing over

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when two homologous sequences or chromosomes are not perfectly aligned

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Transposable elements

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segments of DNA sequence which can self replicate and become inserted into other regions of the genome

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Karyotype

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the description of an organisms complement of chromosomes: Number, size, shape, internal arrangment

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Polyploidy

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when an organism has multiple sets of homologous chromosomes

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Chromosome rearrangements

Inversions and translocations

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Inversions- when a section of chromosome is inverted relative to the ancestral state

Translocations- when non-homologous chromosomes break and are united

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Gene flow

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the exchange of genetic material among populations through mating

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Genetic Drift

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the random fluctuation of allele frequencies due to the chance drawing of gametes that will be transferred to the next generation

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Fates of an allele

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Fixation

Loss

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What impacts drift

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population size

allele frequency

breeding system

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Coalescence

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the point where all gene copies for a particular locus can be traced to a single ancestor

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Rules of Evolution by drift

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Allele frequencies fluctuate randomly

Genetic variation at locus declines and is eventually lost

Probability of allele going to fixation equals frequency

new mutation only represented on one chromosome, so frequency equals 1/2N

Genetic drift more significant in small pops

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Effective population size

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number of individuals that equally contribute to the next generation-> who is actually having babies

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Effective Population Size

Sources of variation

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number of progeny

unequal sex ration

natural selection

overlapping generations

Fluctuations in pop size

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Bottleneck

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When a population goes through a period of very small population size. genetic drift more significant and variation lost

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Founder effect

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when a population is established by very few individuals

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Neutral Theory

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many genetic polymorphisms are selectively neutral and are maintained by a balance between drift and mutation