A mouse geneticist selected for increased 12-day litter weight (total weight of a litter of offspring 12 days after birth) in a
population of mice. The 12-day litter weight of the population steadily increased but then leveled off after about 17 generations. At generation 17, the geneticist took one family of mice from the selected population and reversed the selection procedure: in this group, he selected for decreased 12-day litter size. This group immediately responded to decreased selection; the 12-day litter weight dropped 4.8 g within one generation and dropped 7.3 g after 5 generations. On the basis of the results of the reverse selection, what is the most likely explanation for the leveling off of 12-day litter weight in the original population
12-day litter weight is a trait that has an important genetic influence and therefore also a high response to selection
Explanation:
Heritability is a statistical measure of how much of the variation in a given trait can be attributed to genetic differences and how much of trait variation is due to environmental factors. A heritability value close to 1 indicates that almost all of the variability is due to genetic factors, while being poorly influenced by environmental factors. In this case, 12-day litter weight is a trait that exhibits an important genetic component (i.e., a high heritability value), thereby the correlation between parent and offspring will be high and lines selected for this trait will show a high response to selection.
