BIOA01H3 Lecture Notes - Lecture 37: Human Height, Pleiotropy, Phenotype
27 Nov 2018
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BIOA01 Lecture 34: Genetic and Environmental Basis of Complex Traits
- Complex traits include things like height and blood pressure
o Pleiotropy: a single gene that has multiple effects
▪ Quantitative Traits: measured along a continuum with small
intervals between similar people
• Influenced by the environment
o The expressed phenotype is the sum of a person’s
genotype plus their environment and lifestyle
factors
• These traits tend to be influenced by multiple genes
- Genotype vs the Environment
o It is tough to separate the contributions from one’s genotype and the
contributions from the environment towards the displayed
phenotype
▪ We can say the relative contributions of genotype and the
environment predicts variation
• Eg: looking at human height variation
o 80% of the variation is due to genetic differences
o 20% is due to environmental differences
o Genotype and the environment interact in unpredictable ways
▪ There is not one genotype that is best for all environments
▪ There is not one environment best for all genotypes
▪ Therefore we cannot classify the genotypic effects on
phenotype as being good or bad without knowing what effects
the environment has
- Galton’s Data for height
o He collected data from parents much taller the population mean
▪ He plotted their average height and the average height of their
offspring
• Majority of the offspring were observed to be shorter
than their parents
o Were still taller than the population mean
however
o He also collected and plotted date from short parents and their kids
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