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Lecture 12

Notes Lecture 12.odt

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McGill University
Biology (Sci)
BIOL 202
Daniel Schoen

Quantitative genetics continued QTL mapping Difficult to study wt mendelian tools. Need other tools, can use both broad and narrow heritability as tools. Also, relying on markers and linkage maps that connect back to Mendelian genetics. Distinct markers that we can detect as geneticists using special tools. QTL mapping begins wt crosses. You have 2 parents, 2 purebred (inbred) lines. Cross the F1 back to a pure breeding parent (like a tester parent), and get BC (backcross generation 1)--->tomato example Marker genes: want things that are different between the 2 parents the F1 is heterozygous at all the loci, as expected. Now cross the F1 back to the tester parent. What's going to happen if there is crossover? Alot of varieties of progeny can ensue. Now we look at this with respect to tomato weight. Look for a pattern in the fruit weight. There are a bunch of QTLs affecting fruit weight, not just the loci we took to look at. To get more statistically correct about saying that the M3 marker is an affector of fruit weight, we have to obtain an Odds Ratio (Log10 Odds Ratio=Lod Score) Odds ration = Prob (data given that there is a QTL nearby the marker)/Prob (Data given that there is no QTL nearby the marker) DON'T HAVE TO KNOW HOW TO CALCULATE IT FOR THIS COURSE for quantitative traits, expect a lot of QTL's Can do fine mapping (QTL mapping technique) Use Near isogenic Lines (NIL)--->see which regions are active relative tot he position of the different genes. We zoom into the markers, we assume where they are, and the lines are isogenic everywhere else (so they are nearly isogenic)......the genes, we knew their place cuz of sequencing, but weren't too sure of their function, that's what we're trying to figure out Population Genetics, part 1 • the domain of pop. Gen. • Pop gen variation • factors that change allele and genotype frequencies in populations • the effect of random mating alone on population genetic varation : Hardy-Weinberg Theory • What about inbreeding (non-random mating) • Where does population genetic variation come from in the first place: the effect of mutation and migration on population genetic variation Ex: DNAevidence..A friend of the innocent, Kirk Bloodsworth STR=short tandem repeat, (microsatellites) are used in Forensic DNAevidence. Compare evidence Sample to samples taken from suspects need population genetic theory to make the calculation to decide if someone is guilty or not based on number of loci matching suspect to evidence??? make a calculation based on the product of the frequencies. Genetics at the population level (mostly looking at single loci) ex:sickle cell anemia (Hb-S-->V recessive mutation ) can be see more commonly in specific regions land snail colour variation DNAlevel variation • concentrates on collections
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