1. Genetic Variation Notes

2. 1. KEY CONCEPT A population shares a common gene pool.

3. 2. Genetic variation in a population increases the chance that some individuals will survive.
3. Genetic variation leads to phenotypic variation.
4. Phenotypic variation is necessary for natural selection.
5. Genetic variation is stored in a population’s gene pool.
made up of all alleles in a population
allele combinations form when organisms have offspring

4. 6. Allele frequencies measure genetic variation.
measures how common allele is in population
can be calculated for each allele in gene pool

5. 7. Genetic variation comes from mutation, recombination, & hybridization.
8. Mutation is a random change in the DNA of a gene.
can form new allele
can be passed on to offspring
9. Recombination forms a new combinations of alleles.
usually occurs during meiosis
parents’ alleles arranged in new ways in gametes

6. 10. Hybridization is the crossing of two different species.
occurs when individuals can’t find mate of own species
topic of current scientific research

7. Genetic Variation Provide material for natural selection
Brought about by mutation
Creates greater genetic diversity
Allows a species to adapt a new niche in its environment
Leads to natural selection and a better chance of survival!

8. Don’t do #12!!

9. Phenotype

10. Phenotype
The observable characteristic of an organism such as coat color, eye color or size.
Can be caused by genes, environmental factors, or a combination of both.

11. Phenotype Variation
Is a fundamental prerequisite for evolution by natural selection. It is the living organism as a whole that contributes (or not) to the next generation, so natural selection affects the genetic structure of a population indirectly via the contribution of phenotypes. Without phenotypic variation, there would be no evolution by natural selection.

12. Phenotype and Natural Selection
Phenotypes provide an outward appearance for natural selections
Example: The peppered moth color variation was naturally selected according to the color of the forest that it lives within.
If the phenotype white is preferred in a light forest then the black moths find it hard to survive to reproduce thus leaving the white moths to reproduce.

13. Phenotype Variation
Environmental factors are things in an organism's surroundings or lifestyle that can influence it in various ways. For example, body weight in humans may be influenced by genes, but is also influenced by diet. In this case, diet is an example of an environmental factor

14. Phenotype Variation
A lot more is known about the relationship between genes and phenotypes. Let's take the example of hair color. Perhaps there is a gene in rabbits that codes for an enzyme that, in turn, makes a brown-colored pigment in hair follicles. Some rabbits may have genetic differences that cause them to have more or less of this enzyme, or enzyme that works more or less efficiently to produce the pigment. We would expect these rabbits to have different phenotypes, e.g. lighter or darker brown hair, depending on these genetic differences.