Floral traits in plants often play key roles in diversification, in that slight modifications of those traits, if genetically determined, may quickly lead to reproductive restrictions and evolution. Insight into genetic involvement in flower formation is often acquired through selection experiments that expose realized heritability. Lendvai and Levin (2003) conducted a series of artificial selection experiments on flower size (diameter) in Phlox drummondii. Data from their selection experiments are presented in the following table in modified form and content.
Considering that differences in control values represent year-to-year differences in greenhouse conditions, calculate (in mm) the average response to selection over the three-year period.
Table of contents
- 1. Introduction to Genetics51m
- 2. Mendel's Laws of Inheritance3h 37m
- 3. Extensions to Mendelian Inheritance2h 41m
- 4. Genetic Mapping and Linkage2h 28m
- 5. Genetics of Bacteria and Viruses1h 21m
- 6. Chromosomal Variation1h 48m
- 7. DNA and Chromosome Structure56m
- 8. DNA Replication1h 10m
- 9. Mitosis and Meiosis1h 34m
- 10. Transcription1h 0m
- 11. Translation58m
- 12. Gene Regulation in Prokaryotes1h 19m
- 13. Gene Regulation in Eukaryotes44m
- 14. Genetic Control of Development44m
- 15. Genomes and Genomics1h 50m
- 16. Transposable Elements47m
- 17. Mutation, Repair, and Recombination1h 6m
- 18. Molecular Genetic Tools19m
- 19. Cancer Genetics29m
- 20. Quantitative Genetics1h 26m
- 21. Population Genetics50m
- 22. Evolutionary Genetics29m
20. Quantitative Genetics
Heritability
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A chicken breeder has a population of chickens where the average number of eggs laid per hen per month is 34. The narrow-sense heritability is 0.75. With this information is it likely that a breeder could select for an increase in eggs per hen laid each month?
A
No, breeders never know whether they can select for a trait
B
No, the breeder will need to know the broad-sense heritability to determine whether selection could cause an increase in eggs?
C
Yes, because the narrow-sense heritability is 0.75, this means selection is likely to occur

1
Understand the concept of heritability: Heritability in genetics refers to the proportion of observed variation in a particular trait, such as egg production, that can be attributed to inherited genetic factors in contrast to environmental ones.
Differentiate between narrow-sense and broad-sense heritability: Narrow-sense heritability (h^2) considers only the additive genetic variance, which is the portion of genetic variance that can be attributed to the sum of the effects of individual alleles. Broad-sense heritability includes all genetic variance, including additive, dominance, and epistatic variance.
Interpret the given narrow-sense heritability value: A narrow-sense heritability of 0.75 indicates that 75% of the variation in egg production is due to additive genetic factors. This high value suggests that the trait is largely influenced by genetics and can be effectively selected for.
Consider the implications for selection: Since narrow-sense heritability is high, it implies that selective breeding can lead to a significant increase in the number of eggs laid per hen per month. This is because the trait is largely determined by additive genetic factors, which respond well to selection.
Conclude based on the information: Given the high narrow-sense heritability, it is likely that a breeder could successfully select for an increase in egg production per hen per month. This is because the trait is predominantly controlled by genetic factors that can be passed on to the next generation.
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