Population genetics 4b (Textbook) Flashcards
bottle neck
sudden drop in population size
Phenotypic variation + example (2)
Differences in appearance or function
For example, in a population, although the members look alike, they are not identical. You could detect differences in their weight as well as length and diameter of their shells, and individual biochemistry, physiology and behaviour.
Quantitative variation+ex (2)
individuals differ in small incremental ways
For example, humans exhibit quantitative variation in the length of their toes, number of hairs and their height.
When we display quantitative variation in a bar graph, what information does the graph tell us? (2)
The width of the curve is proportional to the amount of variation among individuals and the mean describes the average value of the character.
Qualitative variation
Characters that exist in two or more discrete states. You have either blue or brown feathers.
Polymorphic traits+ex (3)
traits that are associated with two or more genes. Polymorphic traits, such as the difference in skin and eye color and height, result from more than one gene.
So basically more than one form
Polymorphism does not cover characteristics showing continuous variation (such as weight), though this has a heritable component. Polymorphism deals with forms in which the variation is discrete (discontinuous)
How do you describe phenotypic polymorphism quantitatively?
By calculating the frequency of each trait. You take the individual trait number and divide it by total of all the possible trait forms.
For ex: if you counted 123 blue geese, and 369 white in a population of 492, the frequency of blue is 123/492=0.25
phenotypic variation is caused by (2)
genetic differences between individuals and environmental factors
The organism’s phenotype is often the
product of an interaction between its genotype and its environment as environmental factors influence the espression of genes.
Population genetics
Focuses on the genetic variation that exists within a population and how this changed over time due to evolution.
Evolution can be caused by four distinct processes:
- Mutation
- Genectic drift
- Gene flow
- natural selection
Trait
+ how they are determined
Inherited characteristic of an individual related to their appearance, abilities and behaviours.
Some are coded by single genes while others are coded by the result of many genes
Locus
Location of a gene on a chromosome
Changing how common a particular allele is within a population changes
the genetic makeup of the population.
Gene pool
The total genectic variability of a poopulation by all the alles at all the gene loci in all individuals within the population
Sum of allele frewuency and genotype frequencues…
must equal 1
Hardy Weinberg equilibrium (2)
What it is No listing of the 5 conditions
- a null hypothesis for evolution
- A mathmatical model that soecifies the conditions that are nescessary so that allele frequencies and genotype frequencies do not change from one generation to the next
According to Hardy Weinberg, ——-is possible only if all the following conditions are met (6)
genectic equilibrium is possible only if:
1. The population is closed to migration from one another
2. The population is infinite in size
3. No mutation is occuringin the population
4. All geneotypes in the population survive and reprodice equally well
5. Individuals in the population mate randomly with respect to genotype
How to find allele frequency (4)
- List all the Genotypes : RR, RW, WW
- Multiply genotype by 2 or 1 or 0 (recessive when finding dominant) to find the allele. For example finding the R allele you multiply RR by 2, RW by 1 and WW by 0
- Add up the allele (ex: R allele from RR, RW and WW)
- Divide that by total amount of allele for all allele
Finding genotype frequencies
The number of individuals possesing a particular genotype divided by the total number of inidivduals in the sample
What happens if one of the 5 conditions of the Hardy Weinberg model is violated?
A population’s allele frequencies will change over time
How does population migration change allele and genotype frequencies and lead to evolution? (2)
What is this called?
Organisms and their gametes sometimes move from one population to another and may introduce novel alleles into a population shifting its allele and genotype frequencies away from the values perficated by the Hardy Weinberg model.
This is called gene flow
The importance of gene flow in driving evolutionary change within a population depends on (2)
how different the gene pool is between it and other populations and the rate of gene flow into and out of the population
While gene flow increases genetic diversitiy in one population,….. as a result….
It reduces the genetic differences between the populations.
adjacent populations tend to share many of the same alleles and high rates of gene flow can reduce the genetic differentiation between the two groups, increasing homogeneity
Small populations that are the results of bottle necks have low ——- ——- and have limited ——–
genectic diversity
ability to survive unfavourable enironmental changes
