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HMB265H1 (300)
Lecture

Notes taken during lecture


Department
Human Biology
Course Code
HMB265H1
Professor
Stephen Wright

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LECTURE 15 March 8th
MUST USE THE PREIMPLANTATION ARTICLE in introduction
Cannot determine what genes or loci underly the quantitative trait
How to find THE TRAITS underlying IS THE FOCUS OF THESE 2 LECTURES
A quantitative effect attributed to TWO OR MORE important genes (typo on slide)
Called quantitative trait loci
Identified
o180 genes and most of them are additive effect genes that contribute to
human height
oBUT these genes only make up 10% of phenotypic variation seen between
individuals
oSo where do the rest of the genes that contribute to genetic variation are?
oHOW COULD THEY DETERMINE GENES THAT Underly A
QUANTITAtive trait
BY GENETIC MAPPING TECHNIQUES AND BY ASSOCIATING
MOLECULAR MARKERS WITH THIS TRAIT
Molecular markers genes and the different genotypes that associated with them
Alleles and their different combinations that arise
Change in genotype or differences in genotype that can be followed at molecular
level by gel electrophoresis, by looking at DNA and proteins looking at different
banding patterns by sequencing DNA itself
oThen use statistics to identify more than one QTL at one time
To identify QTL:
STEP1: cross individuals inbred but differing at trait of interest
In example, tomatoes
Genetically identical but differ significantly at the trait of interest, size
F1 individuals in between
F1 crossed to get segregating F2 population
Genetic variation is ZERO so any phenotypic variation seen in individuals is
PART OF THE ENVIRONMENT
F2 due to both environmental and genetic influence
STEP2- determine frequency in F2
Group individuals by size
Bell curve followed
STEP3 extract DNA from each of F2 individuals and genotype each for a set of marker-loci
distributed throughout the genome or along all the chromosomes do for all individuals
Genotype each individual at ALL marker loci, including SNPs, FLPs,
microsatellites
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