What is the narrow-sense heritability of seed weight?

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Discussion Overview

The discussion revolves around calculating the narrow-sense heritability of seed weight in beans based on a selection experiment. Participants explore the appropriate formulas and methods for determining heritability, focusing on genetic variance and selection responses.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant proposes using the formula h^2 = Va/Vt, suggesting that the variance due to additive alleles (Va) is 0.88 and the total variance (Vt) is 0.96, leading to a calculated heritability of 0.92.
  • Another participant questions the use of mean weight for variance and asks for clarification on the term "variance" and the meaning of h^2, indicating uncertainty about the calculations.
  • A different participant argues that the initial formula used is incorrect and suggests calculating the selection differential (0.14g) and the selection response (0.08g) instead, proposing to use these values to find heritability.
  • A later reply provides a calculation for heritability using the selection response and selection differential, arriving at a heritability estimate of 0.57.

Areas of Agreement / Disagreement

Participants do not appear to agree on the correct method for calculating narrow-sense heritability, with multiple competing views and formulas presented. The discussion remains unresolved regarding the appropriate approach and resulting values.

Contextual Notes

There is uncertainty regarding the definitions and calculations of variance and heritability, as well as the assumptions made in the initial approach. The discussion highlights the need for clarity on the terms and methods used in genetic calculations.

jena
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Hi,
My Question:

Assume that all phenotypic variance in seed weight in beans is genetically determined and is additive. From a population in which the mean seed weight was 0.88g, a farmer selected two seeds, each weighing 1.02g. He planted these and crossed the resulting plants to each other, then collected and weighed their seeds. The mean weight of their seeds was 0.96g. What is the narrow-sense heritability of seed weight?

Work

I know that I'm supposed to use this equation:

h^2= Va/Vt, where

Va is the variance due to additive alleles

Vt is the total variance, so I did this

h^2= .88/.96 =.92

Is this correct??

Thank You:smile:
 
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jena, I'm afraid I have no recollection of this area of genetics (you've finally stumped me). :redface: I hope someone else will come along who can better help you, but in the meantime, perhaps we can figure this out together. In your equation, why did you use the mean weight for the variance? How is the term "variance" being used? Also, what does the term h^2 mean? Is that heritability? And do you need to take the squareroot of your final answer to get h (if that's the right term to use there)?

Maybe if you can answer my questions, it will help you find your own answers to how to solve this problem to double-check your work.
 
Could this work :confused:

Selection Differential(difference between the mean phenotype of the selected parents and the mean phenotype of the population before selection)
1.02g-.88g= .14g

Selection Response(Amount phenotype change in one generation)
.96g-.88g=.08 g

then divide the selection reponse response over the selection differential

HN2 =.08/14

Finally,

HN2 =.57
 
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