Multifactorial/complex traits are traits which don't exhibit simple Mendelian genetic inheritance. Instead, they exhibit complex genetic interpretation and depend on several different alleles for their genotype

Continuous traits are genetic traits that vary continuous (basically remain the same) from one phenotypic extreme to the other. Examples include height, blood pressure and corn yield. These traits are usally reflective of the genotype/phenotype of the individual's parents

Categorical traits are traits in which the phenotype falls into a discrete category. Examples include the number of eggs laid and the number of pups in a litter. These traits are typically stable but can vary depending on conditions and simple random chance

Threshold traits are traits that usually have two phenotypic categories but inheritance is determined by effects of multiple genes and environmental factors. Examples include the likelihood of having twins and the likelihood of developing breast cancer

1. Effects of one gene can be masked by effects of other genes and these two genes will probably segregate independently. 2. Environmental effects can cause individuals with identical genotypes to have different phenotypes

The distribution is a description of the population in terms of the proportion of individuals that have each of the possible phenotypes. Variation within this can be entirely genetic, environmental or a combination of both

The mean occurs right at the peak of the distribution. If there is no set peak then you add up all of the numbers and divide by the total amount of numbers present

Variance is given by squaring the mean minus the x value of interest and summing all of these values up and then dividing by the total amount of samples minus one (sigma²=(E(x-x_i)²)/N-1

The standard deviation is the sqaure root of the variance. A bell curve is called a normal distribution

Variation can be separated into genetic and environmental components. Genotypic variance (represented by sigma_g²) is the variation in phenotype caused by difference in genotype and environmental variance (represented by sigma_e²) is the variation in phenotype caused by the environment

It will happen when the genetic and environmental effects contribute independently to the phenotype

Genotype-environment interaction means that environmental effects on the phenotype differ according to genotype

This type of interaction is where the same genotype produces different phenotypes in males and females (for example, height distribution)

The phenotypic variation becomes equal to the environmental variance. The same applies applies for when an environment is the exact same except that phenotypic variation is now only due to genotypic variation

You can calculate the genotype variance using the phenotypic variance of the F2 generation and the environmental variance of the F1 generation

Broad sense heritability is the ratio of genetic variation to phenotypic variation. It can be calculated by using sigma_g²/sigma_g². When H squared=1 then the variation is all genetic and when H squared=0 the variation is all environmental

Since identical twins have a genotypic variability of 0 and fraternal twins have a genotypic variability of 1/2 that of regular people you know that the overall genotypic variability will equal twice (the phenotypic variability of fraternal twins plus the genotypic variability of identical twins)

They tend to over-estimate this figure because environment experienced by twins is usually very similar

Artificial selection is managed evolution. A select group of individuals is selected from a population to become parents of the next generation

NSH is the proportion of phenotypic variance transmissible from parents to offspring. The formula is h²=(M'-M)(M*-M)

Correlated response is the effect of selection for one trait on a non-selected trait. This means that although one trait is being optimized another might be negatively impacted by this sort of forced selection

Inbreeding depression is a decrease in fitness due to harmful recessive alleles which become homozygous over time

A candidate gene is a gene that researches make an educated guess that genetic variation within that gene might affect a certain trait