1. Clover tongue is the ability to roll ones tongue into three distinct lobes an
ID: 45815 • Letter: 1
Question
1. Clover tongue is the ability to roll ones tongue into three distinct lobes and is probably inherited as a dominant, simple Mendelian trait. In a population 90.25% of individuals can NOT roll their tongue into a clover tongue (i.e. they do not possess the clover tongue trait). What is the expected frequency of heterozygous individuals in this population?
2. Assume that in the F2 of a series of crosses, 1/256 of the offspring resemble one of the parents. How many gene loci are involved in producing these results?
3. Assume that three gene loci are involved in determining phenotypes of F2 in an additive manner. How many phenotypic classes are expected?
4. The following values were estimated for corolla length in a population of honey-suckle. What is the narrow-sense heritability for 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 large cornfield in Iowa and found to have a mean level of 28.2 mg per gram and a variance of 15.3. Seeds were collected from these plants and germinated in a single, large greenhouse allowing all plants to germinate and grow under identical environmental conditions. At maturity, 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 in this cornfield population of milkweed? Remember that H2 = broad-sense heritability = VG/VP.
0.9500Explanation / Answer
1. Frequency of homozygous dominant allele for clover tongue = 0.9025
Frequency of homozygous recessive allele for clover tongue = 0.0025
Frequency of heterozygous allele for clover tongue = 0.0950. Option 3 is correct.
2. 4 gene loci must be involved because the offspring are produced in 9:3:3:1 ratio.
3. Three gene loci involved are involved and phenotypic classes can be calculated by 2n+1. Hence 2x3+1 = 7. Option 3 is correct.
4. Narrow sense heretability is defined as the proportion of total phenotypic variation due to heritable effects. It is expressed as VA / VP = h2 . The narrow-sense heritability for this trait for corolla length in a population of honey-suckle is VA = 2.6. Option 2 is correct.
5. The estimated broad-sense heritability for this trait in this cornfield population of milkweed
h2 = VA / VP
VA = 15.3+8.70= 24
VP = 28.2+33.2=61.4
h2 = 24/61.4 = 0.390
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