Chapter 20.2 - Measuring Genetic Variation Flashcards
What is allele frequency?
The allele frequency is the proportion among all the alleles of a gene in a population that consists of a specified allele.
What is allele fixation?
Fixation is the process by which one allele replaces all of the other alleles in a population.
What is genotype frequency?
The genotype frequency is the proportion in a population of each genotype at a particular gene or set of genes.
How are allele frequencies calculated using DNA sequencing?
Amount of “X” allele present / total number of alleles
What are polymorphisms?
Polymorphisms are any genetic difference that are present in multiple individuals in a population.
What does it mean to say that an allele is “fixed” in a population?
An allele is fixed if there is only one allele for that gene in the population.
Its frequency is 100%.
Why, before the invention of molecular tools in the 1960s, was genetic variation so hard to measure?
Before the advent of molecular tools, phenotypes were used to measure genetic variation. Since phenotypes were used, it was difficult to observe differences in the underlying genetic differences.
What is protein gel electrophoresis?
Protein gel electrophoresis is a standard laboratory technique in which charged proteins are transported through a gel matrix.
Has the application of DNA sequencing to population genetics revealed more or less genetic variation in natural populations than previous methods (such as protein gel electrophoresis)?
It has revealed more.
For example, take a protein variant found by protein gel electrophoresis. Now, the DNA of multiple copies of that allele can be sequenced and amino acid differences can be found.
In a survey of DNA sequences from a population of 500 mice, we find 1 polymorphic nucleotide position, which is either G or T. We find 800 G’s on our sample; what is the frequency of the T allele?
500 individuals * 2 alleles per mouse = 1000 alleles within mouse population
G = 800; therefore,
1000 total alleles - 800 G alleles = 200 are T.
200 T alleles/1000 total alleles = 0.2 = 20%
What are the limitations of protein gel electrophoresis?
This technique can only find changes in the amino acids that lead to alterations in the way a protein moves in the gel.
