Plant Bio 2 Final Rafa

Genetics

The study of inheritance of traits, the nature of genes, and how genes work; more broadly, includes regulatory regions controlling gene expression and epigenetic effects.

Genotype

The genetic makeup of an individual; can refer to one gene, multiple genes, or the whole genome.

Phenotype

The traits or characteristics expressed by an individual; the product of the genotype and the environment.

Polygenic trait

A trait that is affected by multiple genes in combination with the environment (common in trees).

Homozygous

An individual with two identical alleles of a gene (e.g., RR or rr).

Heterozygous

An individual with two different alleles of a gene (e.g., Rr).

Dominant allele

An allele that, if present, gives the same phenotype in both heterozygous and homozygous individuals.

Recessive allele

An allele that is masked in heterozygous individuals and only expresses a phenotype in homozygous individuals.

Co-dominance

A condition where heterozygous individuals express both alleles simultaneously.

Incomplete dominance

A condition where heterozygous individuals express an intermediate phenotype between the two homozygous phenotypes.

Genetic drift

Random changes in allele frequency from generation to generation, resulting in genetic change over time and a loss of genetic variation, especially in small populations.

Effective population size (Ne)

An estimate of the genetic population size inversely proportional to the rate of loss of variation due to genetic drift; typically ranges from 10–50% of the actual number of individuals in a population.

Mutation

A change in DNA sequence; can occur during meiosis, mitosis, or due to DNA-damaging agents such as UV radiation. The rate is approximately one in a billion base pairs per year on average.

Somatic mutation

A mutation occurring during mitosis (not meiosis); also called a 'branch sport.' Many horticultural varieties are clones of this.

Gene flow

The movement of individuals (e.g., seeds) or gametes (e.g., pollen) between populations.

Effect of high gene flow

Increases genetic diversity within populations and decreases genetic differences between populations.

Inbreeding depression

The reduction in seed viability, growth rate, and overall fitness that results from inbreeding (mating between relatives or self-pollination) in outbreeding species such as most conifers.

Inbreeding coefficient (F)

A measure of loss of genetic diversity due to inbreeding; the most extreme case is selfing.

Observed heterozygosity (Ho)

The proportion of individuals in a population that are heterozygous at a given locus, measured directly from a sample.

Expected heterozygosity (He)

The proportion of heterozygotes expected under Hardy-Weinberg equilibrium, calculated from allele frequencies using He = 2pq.

Hardy-Weinberg Equilibrium

The principle that allele and genotype frequencies in a population remain constant across generations in the absence of evolutionary forces; expressed as p² + 2pq + q².

Ho << He (implication)

Indicates non-random mating (inbreeding) in the population; the greater the difference, the more inbred the population.

Genecology

The study of intraspecific genetic variation in relation to environmental conditions; a blend of genetics and ecology focused on patterns of adaptation across populations.

Common garden experiment

An experiment in which different genotypes are planted together to minimize environmental differences, allowing genetic differences in traits to be observed. Used in provenance and progeny trials.

Provenance trial

A common garden experiment comparing genotypes from different geographic origins to assess local adaptation.

Progeny trial

A common garden experiment evaluating the genetic quality of selected parent trees by comparing their offspring (families).

Phenotypic plasticity

Changes in an organism's behavior, physiology, or morphology in response to environmental factors, without a change in genotype.

Local adaptation

The process by which populations become genetically better suited to their local environment through natural selection over generations.

Clinal variation

A gradual change in a trait or allele frequency across a geographic or environmental gradient; often observed in provenance trials.

Heritability (h²)

The proportion of phenotypic variation in a trait that is due to genetic (additive) variance; ranges from 0 (no genetic control) to 1 (total genetic control). Formula: h² = VA / VP.

Additive genetic variance (VA)

The component of genetic variance that contributes to resemblance between parents and offspring and determines response to selection.

Phenotypic variance (VP)

Total variation in a trait in a population; VP = VG + VE, where VG is genetic variance and VE is environmental variance.

Selection differential (S)

The difference between the mean of selected individuals and the population mean; S = X̄_selected − X̄_population.

Genetic gain (G)

The predicted change in a trait mean from one generation to the next due to selection; G = h² × S.

Genetic rescue

The introduction of genetic variation (individuals or pollen) into a small, inbred population to reduce inbreeding depression and reverse the effects of genetic drift.

In situ conservation

Conservation of species (and populations) within their natural habitat, typically through protected areas.

Ex situ conservation

Conservation of genetic material away from natural locations, such as in seed banks, clone banks, or tissue culture.

Inter situ conservation

Conservation away from natural locations but often within the historical range of a species; includes provenance and progeny trials.

SNP (Single Nucleotide Polymorphism)

A difference of a single nucleotide at a specific position in the genome between individuals; the most common type of genetic variation used in genomic studies.

Genomic selection

A method of accelerating conventional tree breeding and increasing genetic gain by using genome-wide SNP data to predict the breeding value of individuals.

Assisted gene flow

A conservation/management strategy of moving pre-adapted genotypes from warmer or drier provenances to populations expected to experience future climate change, to improve adaptation.

Assisted species migration

Moving entire species to new areas outside their current range to track shifting climate conditions; a more drastic intervention than assisted gene flow.

Predictive provenancing

Selecting seed sources or genotypes predicted to be well-adapted to future climate conditions at a given planting site.