qtl - Mapping genes for complex traits/diseases Most...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Mapping genes for complex traits/diseases • Most interesting traits are quantitative (high, weight, milk yield, etc.) and controlled by a number of genes and also strongly influenced by the environment – No single gene shows perfect segregation with the trait – Generally, Multiple loci contribute – Environmental effects are also important Complex traits (cont.) • Even if only a single gene underlies the trait, genetics can still be complex – incomplete penetrance, variable expressivity – Phenocopies -- individuals showing the trait for strictly environmental reasons. • Even traits that appear binary (disease is present/absent) can result from a number of interacting genes – Here the quantitative trait is the risk (penetrance) given a particular genotype The Genetics of Human Disease • Can score individuals as affected / unaffected • Alternatively, if known, the appropriate underlying physiological variable can be used as a quantitative character – Blood pressure vs. hypertension (affected / normal) • In most cases, don't know underlying biochemical variables. • How to we find and map such underlying genes? Mapping genes underlying complex traits • QTLs ( Quantitative Trait loci ) -- those underlying quantitative traits • DS ( Disease susceptibility ) genes -- those influencing an individual's susceptibility to a particular disease (e.g., heart disease, Alzheimer's). Note that DS genes are simply QTLs that influence a disease.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Approach 1 for mapping: Candidate genes If one has some biochemical/developmental understanding of the trait/disease, then one can test to see if specific genes in known pathways are involved Variation seen in the population can map to allelic (i.e., DNA sequence) variance in particular candidate genes . Note that just because a gene is involved in a pathway leading to the trait does not mean that trait variation is due to genetic variation in that trait. One looks for associations between the trait and the average values for particular alleles at the candidate gene Example: Apo E (Apolioprotein E) • ApoE gene known to be involved in cholesterol metabolism – Each copy of allele e 4 found to increases cholesterol level by 5-10 – Each copy of allele e
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 12/09/2009 for the course ECOL 320 taught by Professor Weinert during the Spring '07 term at Arizona.

Page1 / 6

qtl - Mapping genes for complex traits/diseases Most...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online