Topic 9: Quantitative Genetics Flashcards
________ traits: traits controlled by more than one gene, they assort independently and produce many possible genotypes
polygenic traits
__________ traits: “multiple factors”, such as genes and the environment
multifactorial traits
phenotypes are _______, showing a continuous phenotypic variation (traits can be described in a unit of measure)
quantitative
________ traits have discrete categories, and display a ________ phenotypic range
qualitative, discontinuous (lead to predictable phenotypic ratios)
________ traits have _________ variation
quantitative, continuous (phenotypic variation is continuous along a range)
quantitative traits have ___________
genetic potential (whether you reach that maximum potential is dependant on the influence of all other factors) (ex: height, if you have tall parents, you have the potential to also be tall)
_______ genes: genes that contribute more to the trait than others
major genes
________ genes: contribute to a trait in small amounts
modifier genes
what is an example of a quantitative trait with major and modifier genes?
eye colour
number of alleles is denoted by what variable?
n (also known as the number of events)
- diploid (2 allels/gene)
- random mating/ cross multi-locus heterozygotes
- contributing alleles only have an additive effect on the phenotype
- no linkage between the genes
- no interactions between the genes
- no environmental effects
- discrete phenotypic categories
these are all conditions to using what expression?
the binomial expression (few traits meet these assumptions, especially in natural populations)
_______ genes: incremental contributions from multiple genes, have a continuous phenotypic range
additive genes (also contributing genes)
Hermann Nilsson-Ehle proposed the _________ hypothesis, segregation of alleles from multiple genes contributes to phenotypic variation
multi-gene hypothesis
true/false: the more phenotypes that occur along the phenotypic range, the narrower the frequency distribution of each category… the more classes we have, the more it appears to be blending (colours become more and more similar to each other)
true!
in 1916, Edward East conducted experiments on ______ plants, concluding that the tube-length was multi-gene but also influenced by nongenetic effects (environment)
tobacco
true/false: gene-environment interaction doesn’t result in phenotypic spread
false! it does, when there is extensive GxE interactions there is SIGNIFICANT phenotypic overlap
______________: values of a trait on a quantitative scale
frequency distribution (use this to quantify phenotypic variation!)
______: small portion of a population
sample
__________: what a sample represents
population
mean: ______
average
Mode: _________
most common value in the distribution