BIOL 2030 Lecture Notes - Lecture 11: Quantitative Genetics, Twin Study, Heritability

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blushwoodchuck89

13 Feb 2016

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Fundamental focus variance in the group of individuals of interest in the population of interest. Phenotype variance: vp can be measured in the group: ex. height can measure everyone in the group and, vp = vg + ve + vge calculate the variance between individuals. Some of the phenotypic variance is due to difference in genotypes vg. Some is due to environment ve. Some is due to genetic-environment interactions . Vge: vg = va + vd + vi. Vi = interaction genetic variance (many genes at work) Broad sense: h2 = vg/vp (range: 0-1) Estimating relative proportion of the phenotypic variance due to genetic variance. Narrow sense: h2 = va/vp (range: 0-1) The relative proportion of the phenotypic variance due to additive variance. Additive variance gives us a good prediction of phenotypes of offspring: parents transmit half their genes to. Do not transmit genotypes progeny reshuffling of genotypes.

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Hey guys! I'm a little stuck with this question, with calculating the total genetic variance I'm not sure whether my answers are correct.

(VG = VA + VD = VI

(Broad sense heritability) H2 = VG/VP

(Narrow Sense heritability) h2 = VA/VP

(Response to Selection) R = h2 x s

A plant breeder has determined the following variances for yield of corn:

Total phenotypic variance 100

Additive genetic variance 30

Dominance genetic variance 50

Environmental variance 20

Assume that there is no genetic-environmental interaction or other variances. a) Calculate the total genetic variance.

b) Calculate the broad-sense heritability indicated by these results.

c) Calculate the narrow-sense heritability indicated by these results.

d) The breeder wishes to improve yield. The average yield in the starting population is 400. Plants with an average yield of 500 are selected for breeding. What is the expected average yield among the offspring of the selected plants?

sangriaskunk539

1. Clover tongue is the ability to roll ones tongue into threedistinct lobes and is probably inherited as a dominant, simpleMendelian trait. In a population 90.25% of individuals can NOT rolltheir tongue into a clover tongue (i.e. they do not possess theclover tongue trait). What is the expected frequency ofheterozygous individuals in this population?

2. Assume that in the F2 of a series of crosses, 1/256 of theoffspring resemble one of the parents. How many gene loci areinvolved in producing these results?

3. Assume that three gene loci are involved in determiningphenotypes of F2 in an additive manner. How many phenotypic classesare expected?

4. The following values were estimated for corolla length in apopulation of honey-suckle. What is the narrow-sense heritabilityfor this trait in the population?

VE = 4.2

VA = 2.6

VD = 0.9

VI = 0.3

5. Toxin levels were measured in milkweed plants from a largecornfield in Iowa and found to have a mean level of 28.2 mg pergram and a variance of 15.3. Seeds were collected from these plantsand germinated in a single, large greenhouse allowing all plants togerminate and grow under identical environmental conditions. Atmaturity, toxin levels were assessed across all of these plants.The mean toxin level was 33.2 mg per gram with a variance of 8.70.What is the estimated broad-sense heritability for this trait inthis cornfield population of milkweed? Remember that H2= broad-sense heritability = VG/VP.

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BIOL 2030 Lecture Notes - Lecture 11: Quantitative Genetics, Twin Study, Heritability

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