Population Genetics Flashcards
What is variation?
Describes the differences in characteristics or phenotypes in organisms of a population
What is a phenotype?
An organisms physical appearance, constitution and behavior
What is a genotype?
An organisms genetic makeup
What is the difference betwen intraspecific and interspecific variation?
Intraspecific variation is variation within a species
Interspecific is variation between different species
What are the two factors of variation?
Genetic variation- characteristics that fall into a limited number of distinct forms
Environmental factors- characteristics that that vary only slightly between individuals due to theire environment
State three examples of genetic factors that cause variation
Meiosis
Mutations
Random fusion of gametes
How can data from genetic variation be represented?
On pie charts, bar charts and histograms
Gove examples of environmental factors that cause variation
Diet, disease, climate change
How are environmental factors of variation represented? What is a key feature of this?
Frequency curve- shows a normal distribution curve
Mean= mode= median
How can gene mutations lead to the production of non-functioning proteins?
A gene mutation alters the base sequence of DNA, which a,ters the base seauence of mRnA after transcription
This can lead to changes in the sequence of amino acids in a protein, hence changing the primary structure
This can change the tertiary structure as hydrogen, ionic and disulphide bonds form in different places
Leads to loss pf function of a protein
What are mutagenic agents? Give two examples
Agents that increase the rate of base mutations
X-rays and UV lights
State six types of mutations
Addition
Deletion
Substitution
Duplication of bases
Inversion of bases
Translocation of bases
What are addition and deletion mutations? What type of mutation do they both cause?
Addition is where an extra base is added to the sequence
Deletion is where a base is removed from the sequence
Both lead to frame shift mutation- they both change all triplet codes, so the whole sequence of amino acids changes
What are substitution mutations?
Where one base in the sequence is swapped for another
State and explain the three different consequences of substitution mutations
Mis-sense- one amino acid in the polypeptide changes. This can change both primary and tertiary structure
Silent- no difference due to the degenerate nature of the triplet code. The new triplet codes for the same amino acid
Nonsense- base change results in the dormation of a stop codon. Translation stops
What is a duplication of bases mutation? What type of mutation does this cause?
Where aone or more bases are repeated. This causes a frame shift mutation to the right
What is an inversion of bases mutation?
Where a group of bases are seperated from the sequence and rejoin in the same position of the sequence, but in the inverse order
What is a translocation of bases mutation?
A group of bases are separated from the sequence, and are inserted into the same or different chromosome in a different position.
What are introns?
Non coding sections of genes
What is a population?
All the individuals of one species in the same habitat at any given time, that can interbreed to produce fertile offspring
What is the gene pool?
The set number of alleles of all the gene loci in a population at a particular time
How do you calculate allele frequencies that show codominance?
Calculate the total number of alleles in the population (population size x2 as there are 2 alleles in every gentoype)
Calculate the frequency of a particular allele (times number of homozygous plants by two and add to number of heterozygous plants)
Divide by total number of alleles
What is the hardy weinburg equation used for?
To calculate the proportion of each allele (allele frequency)
In the hardy weinburg equatipn, what does each letter represent?
P= frequency of the dominant allele
q= frequency of the recessive allele
p^2= frequency of the homozygous dominant genotype
q^2= frequency of the homozygous recessive genotype
2pq= frequency of the heterpzygous genotype
What does the hardy weinburg principle state?
That the frequency of the alleles of a particular gene in a population will stay contstant from generation to generation
What conditions does the hardy weinburg principle take place under?
Large population
Mating between indiciduals must be random
No mutations
All genotypes equally likely to reproduce
No immigration or emigration
What does it show when the hardy weinburg principle is not correct?
That species are constantly in a state of evelutionary flux
What is genetic drift?
The idea that allele frequencies can change simply due to chance
In what sozed population is genetic drift most likely to occur?
In small populations, as the changes that pccur due to chance will have a greater influence on allele frequency, as there are less of them to counteract the chanced event
What are two examples of genetic drift?
The founder effect
Genetic bottlenecks
What is the founder effect in genetic drift?
When a few organisms become isolated from the population, this will decrease the population size so the impact of chance on the allele frequencies would be greater
What is genetic bottlenecks in genetic drift?
When the majority of individuals are killed, so the population is reduced to a very small number.
A decreased populatipn size increases the impact of chance on the allele frequencies.
