Question

You raise plants in a controlled growth room, using seeds collected from a natural population. You measure leaf length of adult plants, select the plants with longest leaves, and raise their offspring in the growth room. You find that leaf length in the second generation is 10 cm longer than in the first generation. Using seeds from the same population, you do the same experiment in a field environment, applying the same strength of selection. You find that leaf length in the second generation is only 5 cm longer than in the first generation. Referring to concepts in quantitative genetics (e.g., components of VP) provide a plausible explanation for the difference in the amount of trait change in the two environments.

Answer 1

Quantitative genetics is a branch of genetics that primarily deals with characters that varies continuously,and are hence quantified by allele frequencies of different gene by quantitative trait locus(QTL) study.We know that variation in phenotype is a combination of variation in genes and variations in environment.
Vp= Vg + Ve
In this example the leaf length in both cases for first generation had similiar genotype ( i.e. seed from same population),but the environmental conditions varied.Supposing there is a gene resposible for leaf length,which will be most probably polygenic gene,now the combination and frequency of different alleles that are passed on to generation varies depending on the genetic and environmental factors.The effect of environment and genetics were added up in the second generation as for them the genetic background and environmental conditions both varied.So ultimately we see a combined variation of 5cm in leaf length which is attributed to both Vg and Ve.

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