Genetics Help: (1) Two homozygous varieties of Nicotiana longiflora were crossed

Question

Genetics Help:

(1) Two homozygous varieties of Nicotiana longiflora were crossed to produce F1 hybrids. The average variance of corolla length for all three populations (i.e., parentals and F1) was 8.76 mm. The variance of the F2 was 40.96 mm. Estimate the heritability of flower length in the F2 population. Define heritability.

(2) In a plant, height varies from 3 to 36 cm. When 6-cm and 36-cm plants were crossed, all F1 plants were 21-cm. In the F2 generation, a continuous range of heights was observed. Most were around 21-cm, and 3 of 200 were as short as the 6-cm P1 parent.

(a) How many genes are involved in controlling plant height?_____________

(b) How much (in cm) does each additive allele contribute to height?_______

(c) List three different genotypes that give rise to plants that are 31 cm?

Explanation / Answer

Answer:

1. Since the two parental varieties and F1 are genetically uniform, their average phenotypic variance is an estimate of the environmental variance (Ve). The phenotypic variance of the F2 (Vt) is partly genetic and partly environmental. The difference (Vt-Ve) is the genetic variance (Vg)

h2 = Vg/Vt = (Vt-Ve)/Vt = (40.96-8.76) / 40.96 = 0.79

Heritability is defined as the proportion of observed variation in a particular trait (such as height) that can be attributed to inherited genetic factors in contrast to environmental ones.

(Since there are more than 1 question, the first full question have been answered according to the rules of Chegg)

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