1. Genetic Diversity in Populations
Chapter 19
Genetic Diversity in Populations

2. Chapter Outcomes: Define a gene pool.
Describe the gene pool of a population at genetic equilibrium.
Summarize the five conditions upon which the Hardy-Weinberg principle is based.
Describe how the Hardy-Weinberg equation is used to determine whether a population is undergoing microevolution.

3. Chapter Outcomes
Calculate allele and genotype frequencies in a population.
Outline the conditions required to maintain genetic equilibrium.
Identify and compare the effects of mutations, gene flow, non-random mating and genetic drift on gene pool diversity.
Apply the Hardy-Weinberg principle to published data.

4. Chapter Outcomes
Distinguish between founder effect and the bottleneck effect on gene pools.
Explain how the process of natural selection is related to microevolution.
Explain the cause of heterozygote advantage and how it affects a gene pool.
Describe strategies used in captive breeding and population management.
Explain that genetic engineering can have intended and unintended effects on gene pools.

5. Genetic Diversity in Populations
Recall that a population is a group of organisms of the same species living in one area
Within a population, there are many genes
The sum of the genes (and their different alleles) is known as the gene pool
Gene pools are studied by population geneticists

6. Genotype, Phenotype & Allele Frequency
Genotype Frequency:
Phenotype Frequency:
Allele Frequency:

7. The Hardy-Weinberg Principle
the Hardy-Weinberg principle predicts that if other factors remain constant, the gene pool will maintain a constant composition over many generations
this is expressed by a mathematical equation:

8. The Hardy-Weinberg Equation
p2 + 2pq + q2 = 1
Where:
p is the frequency of the A allele
q is the frequency of the a allele
if the values of p and q are known, we can calculate the frequency of the alleles AA, Aa, and aa (and vice-versa)

9. Limits to the Hardy-Weinberg Principle
Large populations
Random mating
No mutations
No migration
No natural selection against any of the phenotypes

10. Application of the Hardy-Weinberg Principle
In a population, we know that a dominant trait is present 82% of the time. Determine the percentage of individuals that make up each genotype.

11. The Hardy-Weinberg & Population Change
If a gene pool changes over time, one of the 5 conditions it is based on must also have changed
Therefore, the strength of this principle is to determine whether or not a population is evolving
The Hardy-Weinberg equation also allows us to determine what percentage of a population are “carriers” of a trait

12. Evolutionary Change gene pools are unstable
factors that bring about evolutionary change are mutation, genetic drift, and migration (or gene flow)

13. Mutation

14. Gene Flow

15. Non-Random Mating

16. Genetic Drift

17. The Founder Effect
New populations are often formed by only a few individuals (Founders)
The founders will only carry part of the original gene pool from the population
Therefore, the new gene pool will be limited

18. The Bottleneck Effect
Starvation, disease, human activities, or natural disasters can quickly reduce a large population
The survivors only have a subset of the alleles present before the disaster, and therefore, the gene pool loses diversity
Gene pool change caused by a rapid decrease in population is known as the bottleneck effect

19. Examples of the Founder Effect
“Blue Fugates”
Philadelphia Amish

20. Examples of the Bottleneck Effect
Northern Elephant Seals
Cheetahs

21. Natural Selection
Natural selection is the only process that leads directly to evolutionary adaptation
Recall that natural selection occurs in the following order:

22. Advantage & Natural Selection
Sexual Selection:
Heterozygote Advantage & Lethal Alleles:

23. Human Activities & Genetic Diversity
Humans can affect genetic diversity of populations in many ways:
Habitat fragmentation
Unregulated hunting & habitat removal

24. Biotechnology & Gene Pools
We can use many techniques to modify organisms and the gene pools of populations
We now have added genes to species that come from completely different species, thereby adding a gene to a gene pool that most likely would never have been there otherwise

25. These genes could be passed on to others in a population
This could ultimately affect the process of natural selection
As well, because genes do not work alone (often they work together), the positive effect of the inserted genes may be negated because the gene affects other traits necessary for survival

26. Cloning to Save Species
Cloning can be one way to preserve gene pools
Creating clones of endangered species could reverse the threat of extinction
In 2000, a cloned Asian gaur (a rare ox-like mammal) was born in Iowa to a domestic cow that served as a surrogate mother