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Ch. 25 - Quantitative Genetics and Multifactorial Traits

Chapter 24, Problem 18

In a population of tomato plants, mean fruit weight is 60 g and h² is 0.3. Predict the mean weight of the progeny if tomato plants whose fruit averaged 80 g were selected from the original population and interbred.

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Hey everyone. Let's take a look at this question. Together, A fisherman decided to increase the growth rate of fish in his pond. He chose the longest fish by six weeks for breeding, which was 20 centimeters. The mean length of the fish population in his pond was centimeters. And the narrow sense heritability for the length of this fish population was found to be 0.5 determine the mean length of the fish population in the next generation. So for this problem we are going to use that narrow sense heritability which in this case H. Squared equals R. Over S. Where R. Is the selection response and it is the mean of the offspring minus the overall mean. And then s is that selection differential which is calculated as the mean of the parents minus that overall me. And so looking at the problem, we note that the narrow sense heritability is 0.5. So we have 0.5 equals and then we plug in our R. And S. Values. So because we don't have this mean of the offspring, because that is what we're trying to figure out in the next generation, we go ahead and do m minus the overall mean, which is 15. So m minus 15 over S. Which S equals the mean of the parents, which we can see is 20. So it's 20 minus that overall mean, which is 15. And we end up with 0.5 equals m minus 15/5. And we go ahead and multiply both sides by five to cancel that out and we end up with five times 0.5 equals m minus 15 and we add 15 to both sides to cancel those out. And we end up with 2.5 plus 15 equals M. So M equals 17.5, which is answer choice C. The correct answer. Because when we use that narrow sense heritability formula and plug in the values from the question, we end up with 17.5 as our M. Value, which is the mean of the offspring, which is what we're trying to find out because we want to know the mean length of the fish in the population for that next generation. So it is 17.5 and that is centimeters. So answer choice C. Is the correct answer. Hope you found this video to be helpful. Thank you and goodbye.
Related Practice
Textbook Question

In a herd of dairy cows the narrow-sense heritability for milk protein content is 0.76, and for milk butterfat it is 0.82. The correlation coefficient between milk protein content and butterfat is 0.91. If the farmer selects for cows producing more butterfat in their milk, what will be the most likely effect on milk protein content in the next generation?

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Textbook Question

In an assessment of learning in Drosophila, flies were trained to avoid certain olfactory cues. In one population, a mean of 8.5 trials was required. A subgroup of this parental population that was trained most quickly (mean=6.0) was interbred, and their progeny were examined. These flies demonstrated a mean training value of 7.5. Calculate realized heritability for olfactory learning in Drosophila.

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Textbook Question

Suppose you want to develop a population of Drosophila that would rapidly learn to avoid certain substances the flies could detect by smell. Based on the heritability estimate you obtained in Problem 16, do you think it would be worth doing this by artificial selection? Why or why not?

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Textbook Question

In a population of 100 inbred, genotypically identical rice plants, variance for grain yield is 4.67. What is the heritability for yield? Would you advise a rice breeder to improve yield in this strain of rice plants by selection?

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Textbook Question

Many traits of economic or medical significance are determined by quantitative trait loci (QTLs) in which many genes, usually scattered throughout the genome, contribute to expression.

What general procedures are used to identify such loci?

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Textbook Question

Many traits of economic or medical significance are determined by quantitative trait loci (QTLs) in which many genes, usually scattered throughout the genome, contribute to expression.

What is meant by the term cosegregate in the context of QTL mapping? Why are markers such as RFLPs, SNPs, and microsatellites often used in QTL mapping?

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