Complex Traits Practice Flashcards

A set of vocabulary flashcards covering complex traits, inheritance patterns, genetic study methods, and statistical analysis as discussed in the lecture.

Monogenic

A type of trait controlled by just one gene.

Polygenic

A trait where a handful of genes jointly give rise to a characteristic, contributing small effects.

Omnigenic

A theory suggesting that a few core genes are essential, but all genes are involved in the expression of a trait.

Qualitative traits

Traits such as blood type or flower color that are discrete categories and are not strongly influenced by the environment.

Quantitative traits

Traits such as height, BMI, or grain yield that show continuous variation and are heavily influenced by the environment.

Genetic Architecture

The composition of most complex traits involving hundreds of genetic variants, usually SNPs with small individual effects, often in non-coding regions.

SNPs (single nucleotide polymorphisms)

Common genetic variants often located in non-coding regions that regulate gene expression and contribute to complex traits.

Low penetrance

A challenge in complex trait genetics where having a risk gene does not guarantee the presentation of the trait.

Genetic heterogeneity

A phenomenon where different genes can cause the same phenotypic trait.

Quantitative Trait Loci (QTL)

Specific regions of the genome or polygenes associated with the variation of a measurable quantitative character.

Heritability

The proportion of phenotypic variation that can be attributed to genetic variation.

Missing Heritability

The phenomenon where genetic variants identified from GWAS explain only a small fraction of the heritability observed in family studies.

Phenotype formula

A model of quantitative phenotypes expressed as $\text{Phenotype} = ext{Genotype} + ext{Environment} + ( ext{Genotype} imes ext{Environment})$.

GWAS (Genome-wide association studies)

A method used to identify associations between common genetic variants and traits across large populations to find risk variants.

Systems Genetics

An approach combining genetic mapping with intermediate molecular phenotypes, like proteins or transcripts, to understand impacts on biological systems.

Polygenic Risk Scores (PRS)

A predictive tool used in research to estimate an individual's disease risk based on the sum of their risk alleles.

Meristic traits

A type of quantitative trait determined by counts, such as the number of eggs.

Threshold traits

Quantitative characteristics that display only two possible phenotypes (present or absent) but have an underlying continuous susceptibility.

Frequency distribution

A graph displaying the numbers or proportions of different phenotypes present in a group, with phenotypic values on the horizontal axis and counts on the vertical axis.

Normal distribution

A symmetrical, bell-shaped distribution where approximately $95\%$ of values fall within $\pm 2\,\text{SD}$ of the mean.

Bimodal distribution

A phenotypic distribution that displays two distinct peaks.

Mean

A statistical measure providing the average or information about the center of a distribution.

Variance

A statistical measure providing information about the variability or spread of a group of phenotypes.

Standard deviation

A measure of spread in a distribution expressed in the same units as the mean.

Correlation coefficient

A statistical measure for the strength of association between two characteristics, where a change in one is associated with a proportional change in the other.

Regression coefficient

The slope of the regression line indicating how much one value changes on average per unit increase in another variable.