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 are threshold traits?

They are traits that have to reach a specific threshold to determine the specific trait its associated with

What are quantitative traits?

They are traits that show continuous variation (such as height) and is analyzed using mathematical models and statistics with data usually 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 tells us how far individuals differ from the average (aka the mean)

What does a small variance show?

It shows individuals with a specific trait that are tightly clustered around the mean

What does a large variance show?

It shows individuals with a specific trait that are more spread-out from 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 is quantitative trait loci (QTL)?

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

• Height

What does mapping QTL identify? What is it good for?

identifies specific regions on the genome that influences a quantitative trait

• And is good for species where controlled crosses are possible

In QTL mapping, what does it mean if different genotypes show distinct trait distributions?

It indicates a QTL is located near that genetic marker

What is Genome-wide association study (GWAS)?

A research method that uses large naturally breeding populations

Why is linkage disequilibrium (LD) important in GWAS?

GWAS relies on LD to detect genetic markers associated with traits

What genetic markers are used in GWAS to map genome loci associated with a trait/disease?

Genetic markers that don’t cause phenotypic changes

What is the insulin-like growth factor 1 gene?

A gene that encodes a hormone involved in juvenile growth in mammals and is a major contributor to the size difference between small and large dog breeds

What can GWAS be used for?

It can be used for:

• Identifying disease-risk genes

• Predicting susceptibility

• Personalizing medicine