In Nicotiana, two inbred strains produce long (PL) and short (PS) corollas. These lines are crossed to produce F₁, and the F₁ are crossed to produce F₂ plants in which corolla length and variance are measured. The following table summarizes the mean and variance of corolla length in each generation. Calculate H² for corolla length in Nicotiana.

Verified step by step guidance

1. Step 1: Understand the concept of broad-sense heritability (H²). Broad-sense heritability is calculated using the formula: $H{2}^{}=\frac{V{G}_T}{V}$, where $V{G}_T$ is the genetic variance and $V{P}_T$ is the phenotypic variance.
2. Step 2: Identify the phenotypic variance ($V{P}_T$) from the F₂ generation. According to the table, the phenotypic variance in the F₂ generation is 38.10 mm².
3. Step 3: Calculate the environmental variance ($V{E}_T$). The environmental variance can be estimated from the F₁ generation, as F₁ plants are genetically uniform. Therefore, the variance in the F₁ generation (3.62 mm²) is considered the environmental variance.
4. Step 4: Determine the genetic variance ($V{G}_T$) using the formula: $V{G}_T=V{P}_T-V{E}_T$. Subtract the environmental variance (3.62 mm²) from the phenotypic variance (38.10 mm²) to find the genetic variance.
5. Step 5: Calculate H² using the formula: $H{2}^{}=\frac{V{G}_T}{V}$. Divide the genetic variance by the phenotypic variance to determine the broad-sense heritability for corolla length in Nicotiana.

Key Concepts

Heritability (H²)

Heritability (H²) is a measure used in genetics to quantify the proportion of phenotypic variance in a trait that can be attributed to genetic variance among individuals in a population. It is calculated using the formula H² = Vg / Vp, where Vg is the genetic variance and Vp is the total phenotypic variance. Understanding heritability helps in predicting how traits may respond to selection and informs breeding strategies.

Phenotypic Variance (Vp)

Phenotypic variance (Vp) refers to the total variance observed in a trait within a population, which includes both genetic variance (Vg) and environmental variance (Ve). It is essential to distinguish between these components to understand how much of the observed variation is due to genetic differences versus environmental influences. In the context of the question, Vp is derived from the variances of the parental and F1 and F2 generations.

Genetic Variance (Vg)

Genetic variance (Vg) is the portion of phenotypic variance that is attributable to genetic differences among individuals. It can be further divided into additive genetic variance, dominance variance, and interaction variance. In the context of the Nicotiana example, calculating Vg involves analyzing the differences in mean corolla lengths between the parental strains and their offspring, which helps in understanding the heritable component of the trait.