Chapter 19: Complex traits

What type of inheritance do continuous, categorical, and meristic traits have?

They have complex inheritance due to them being associated to more than one gene

What kind of disease falls under categorical traits?

Most mendelian inheritance diseases fall under this category

What is a threshold trait?

A characteristic that develops only if an individuals liability crosses a certain environmental threshold, otherwise the “normal” trait will develop

What is a quantitative trait?

A characteristic that shows continuous variation (such as height) and is analyzed using mathematical models and statistics with data collected from:

• the Population (aka the group that’s being studied)

• A Sample

• the Mean

What is variance?

The deviation from the population mean and how far individuals differ from the average (aka the mean)

What do many quantitative traits follow?

a normal "bell shaped" distribution

What traits are influenced by the environment?

Both complex and mendelian traits

What is able to influence quantitative traits (such as height, weight, and skin color)?

Genetics and the environment

What does the total variance express?

It expresses the sum of genetic and environmental variance

What does broad-sense heritability measure?

It measures how much of the total variance in a trait is caused by genetics

What if twins are raised in different environments?

Any similarities between the twins can be explained by their genetic makeup

What if there is high heritability between twins raised in different environments?

They will exhibit lots of similarities between each other due to their traits being primarily influenced by their genetic makeup

What if there is low heritability between twins raised in different environments?

They will exhibit few similarities between each other due to their traits being primarily influenced by their environment

What are quantitative trait loci’s(QTL)?

Genes that contribute to the variation in a quantitative or complex trait, such as height

QTL mapping is used…

To localize chromosomal regions that greatly affect the variation of quantitative traits in a population

If different genotypes show distinct trait distributions in QTL mapping..

It indicates a QTL is located near that genetic marker

What is Genome-wide association study (GWAS)?

A research method that uses large natural breeding populations

Why is linkage disequilibrium (LD) important in GWAS?

GWAS relies on LD to detect genetic markers associated with traits

Genetic markers that dont cause phenotypic changes are used…

in GWAS to map genome loci associated with a trait/disease

What can GWAS be used for?

It can be used for:

• Identifying disease-risk genes

• Predicting susceptibility

• Personalizing medicine

What is a categorical trait?

A characteristic that can be sorted into discrete categories or groups, rather than being measured on a continuous scale

What is a continuous trait?

A characteristic that can vary in degrees and is measurable across a range, rather than falling into distinct categories

What are meristic traits?

Are characteristics of an organism that are expressed as countable, discrete numbers, like the number of vertebrae or gill rakers in a fish