Quantitative genetics continued
Difficult to study wt mendelian tools. Need other tools, can use both broad and narrow heritability
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
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
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
• concentrates on collections