QuantGeneticLecture2

QuantGeneticLecture2 - Announcement Get Paid($90 to be a...

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Announcement: Get Paid ($90) to be a Notetaker for Genetics Guidelines to be a Notetaker: •Must be enrolled in the class •Must have a standing GPA of 2.5 or higher •Should fill out an application at our office •Notes taken in class should be legible , complete and delivered on a weekly basis to the Office of Disability Services. $ 90.00 will be paid per semester. Interested Students may contact : Debbie Calo, Coordinator / Office of Disability Services, 804 University Avenue, Room 304 - (Across from the Sheraton Hotel) (Take 804 Building Elevator to the 3rd floor) Call the Notetaking Office at 443-5734
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Quantitative Genetics Lecture 2
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4 Quantitative genetics: One more vocab. word Threshold traits: only two, or a few phenotypic classes, but their inheritance is determined by multiple genes and environment
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Quantitative Genetics Lecture 2 Today we will be: •Expanding on Heritability •Introducing QTLs
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• Heritability is the proportion of the phenotypic variance that is attributable to genetic variation H B 2 = V G /V T – Where, H B 2 is the heritability in the broad sense V G is the variance due to genetics V T is the total phenotypic variance H B 2 is called the broad sense heritability • It accounts for all genetic variation that may affect the phenotype Broad versus Narrow Sense Heritability
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Geneticists usually subdivide V G into three different components – V G = V A + V D + V I V A is the variance due to additive alleles V D is the variance due to alleles that follow a dominant/recessive pattern of inheritance V I is the variance due to genes that interact in an epistatic manner In analyzing quantitative traits, geneticists often focus on V A and ignore the contribution of V D and V I The heritability of a trait due to the additive effects of alleles is called the narrow sense heritability h N 2 = V A /V T
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• There are several ways to estimate narrow sense heritability • A common strategy is to: – 1. Measure a quantitative trait among groups of genetically related individuals – 2. Use data to compute a correlation between the individuals – 3. Calculate narrow sense heritability as h N 2 = r obs /r exp – r obs is the observed phenotypic correlation between related individuals – r exp is the expected correlation based on the known genetic relationship » Note: For siblings, r exp = 0.5 » For identical twins, r exp = 1.0 » For parent-offspring relationship, r exp = 0.5 » For uncle-niece relationship, r exp = 0.25
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• Fingerprints are inherited as a quantitative trait • Kristine Bonnevie developed a method for counting the number of ridges within a human fingerprint Heritability of Human Fingerprints
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• Human fingerprints can be categorized as having an – Arch, loop or whorl • The primary difference among these is the presence of the number of triple junctions, each known as a triradius
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• Bonnevie conducted a study on a small population – She found that ridge count correlations were relatively high in
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This note was uploaded on 04/09/2008 for the course EFB 307 taught by Professor Powell during the Fall '07 term at Syracuse.

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QuantGeneticLecture2 - Announcement Get Paid($90 to be a...

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