/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 15 Why does the response to selecti... [FREE SOLUTION] | 91影视

91影视

Log out

Learning Materials

Features

Discover

Chapter 24: Problem 15

Why does the response to selection often level off after many generations of selection?

Short Answer

Expert verified
The response to selection levels off due to reduced genetic variation, environmental factors, genetic correlations, and inbreeding depression.

Step by step solution

01

Define the Concept

In selection, response often decreases over time due to a phenomenon known as 'selection plateau'. This occurs when the population reaches a genetic limit or the heritability of the trait decreases due to various factors.
02

Genetic Limitations

Over time, the genetic variation for the trait decreases as alleles become fixed. This leads to a reduction in genetic diversity, which limits the potential for further improvement through selection.
03

Environmental and Non-genetic Factors

The environment also plays a substantial role. If environmental variation remains constant while genetic variation decreases, the relative impact of genetics on the trait lessens, making it harder to see improvements through selection.
04

Correlated Responses and Undesirable Traits

Selection for a particular trait might inadvertently increase the frequency of undesirable traits due to genetic correlation, which can counteract the intended effects of selection.
05

Inbreeding Depression

Continuous selection often leads to inbreeding, which can bring about inbreeding depression. This results in a reduction of the individual's fitness and may counteract or even reverse the gains made by selection.

Unlock Step-by-Step Solutions & Ace Your Exams!

  • Full Textbook Solutions

    Get detailed explanations and key concepts

  • Unlimited Al creation

    Al flashcards, explanations, exams and more...

  • Ads-free access

    To over 500 millions flashcards

  • Money-back guarantee

    We refund you if you fail your exam.

Over 30 million students worldwide already upgrade their learning with 91影视!

Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Genetic Variation
Genetic variation refers to the diversity in gene frequencies within a population. It is the cornerstone for any evolutionary changes and selective breeding.

Genetic variation arises from mutations, gene flow, and sexual reproduction. These variations lead to differences in traits among individuals, such as size, color, or behavior. Such differences are crucial because they provide the material for selection to act upon.
  • Over generations, selection tends to decrease genetic variation as beneficial alleles become fixed, and harmful ones are lost.
  • This reduction can cause a selection plateau, as further improvements in the selected trait become more challenging.
Maintaining genetic variation is essential for a population's ability to adapt to changing environments and continue improving desired traits.
Heritability
Heritability is a measure of how much of the variation in a trait is due to genetic differences among individuals in a population. Simply put, it tells us the extent to which a trait can be passed from parents to offspring.

Heritability is expressed as a percentage or a value between 0 and 1, where higher numbers mean more genetic influence.
  • For instance, a heritability of 0.6 suggests that 60% of the variation in the trait is due to genetic factors.
  • Low heritability indicates that environmental factors play a larger role.
In the context of a selection plateau, heritability may decrease over time as genetic variation for the trait runs out. This means the role of genetics in further improvement diminishes, making it harder to see continued progress.
Inbreeding Depression
Inbreeding depression occurs when related individuals reproduce, leading to an increased chance of offspring inheriting harmful genetic mutations. This is especially common in small populations where gene pools are limited.

The effects of inbreeding depression can be severe, reducing fitness by decreasing traits such as fertility, growth rate, and resistance to diseases.
  • Inbreeding as a result of continual selection can lead to genetic bottlenecks, limiting diversity.
  • Depression occurs because harmful recessive alleles become more likely to be expressed.
To avoid these negative effects, breeding programs often introduce new genetic material or maintain a larger gene pool to preserve genetic diversity and population health.
Genetic Correlation
Genetic correlation is the relationship between traits that are genetically linked, meaning that selection for one trait may inadvertently affect another.

These correlations arise because some genes may influence multiple traits, known as pleiotropy, or because traits are closely linked on chromosomes.
  • This means selecting for a trait can lead to unwanted changes in other correlated traits.
  • If a negative correlation exists, improving one trait might worsen another.
Understanding genetic correlations is crucial in breeding programs to predict and manage these potential side effects. By considering correlations, breeders can make more informed decisions to enhance desired traits while minimizing negative impacts.

One App. One Place for Learning.

All the tools & learning materials you need for study success - in one app.

Get started for free

Most popular questions from this chapter

Seed size in a plant is a polygenic characteristic. A grower crosses two pure- breeding varieties of the plant and measures seed size in the \(\mathrm{F}_{1}\) progeny. She then backcrosses the \(\mathrm{F}_{1}\) plants to one of the parental varieties and measures seed size in the backcross progeny. The grower finds that seed size in the backcross progeny has a higher variance than does seed size in the \(\mathrm{F}_{1}\) progeny. Explain why the backcross progeny are more variable.

Eugene Eisen selected for increased 12 -day litter weight (total weight of a litter of offspring 12 days after birth) in a population of mice (E. J. Eisen. 1972. Genetics 72:129-142). The 12-day litter weight of the population steadily increased but then leveled off after about 17 generations. At generation \(17,\) Eisen took one family of mice from the selected population and reversed the selection procedure: in this group, he selected for decreased 12 -day litter weight. This group immediately responded to the reversed selection: the 12 -day litter weight dropped \(4.8 \mathrm{~g}\) within 1 generation and dropped \(7.3 \mathrm{~g}\) 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?

The following data are the numbers of digits per foot in 25 guinea pigs. Construct a frequency distribution for these data. $$ 4,4,4,5,3,4,3,4,4,5,4,4,3,2,4,4,5,6,4,4,3,4,4,4,5 $$

List all the components that contribute to the phenotypic variance, and define each component.

Bipolar disorder is a psychiatric illness with a strong hereditary basis, but the exact mode of its inheritance is not known. Research has shown that siblings of patients with bipolar disorder are more likely to develop the disorder than are siblings of unaffected people. Findings from one study demonstrated that the ratio of bipolar brothers to bipolar sisters is higher when the patient is male than when the patient is female. In other words, relatively more brothers of patients with bipolar disorder also have the disease when the patient is male than when the patient is female. What does this observation suggest about the inheritance of bipolar disorder?
See all solutions

Recommended explanations on Biology Textbooks

Plant Biology

Read Explanation

Ecosystems

Read Explanation

Cellular Energetics

Read Explanation

Ecology

Read Explanation

Cell Communication

Read Explanation

Heredity

Read Explanation
View all explanations

What do you think about this solution?

We value your feedback to improve our textbook solutions.

Study anywhere. Anytime. Across all devices.