0430 Population genetics Flashcards
•Describe the implications of population genetics in disease •Describe the factors that influence genetic variation and allelic frequency •Apply Hardy-Weinberg equation •Describe the deviations from the Hardy-Weinberg equilibrium •Explain and provide and example of selective advantage and negative selection
Define a base pair
A base pair is nucleotides. There are the builiding blocks of DNA (ATGC)
Define a gene
A gene is a segment of DNA that codes for a functional RNA product or protein
Define an allele
An allele is one of a number of alternative forms of the same gene
Define genetic locus
A locus is the specific location of a gene or DNA sequence or position on a chromosome
Define a genotype
A genotype is the genetic makeup of a cell, organism or an individual
Define a phenotype
A phenotype is an organism’s observable characteristics or traits
What is a genetic mutation and what is it’s implication in population genetics
Genetic mutation is a change of the nucleotide sequence from damage to DNA or to RNA, errors in replication, or insertion/deletion. It is important in population genetics because it is one of the main factors that affects the genetic make up of a population
What is the the study of population genetics? What is it trying to clarify (in terms of alleles and genes)
Population genetics is a study of how a population changes over time leading to a species evolving/mutating.It is the study of the frequency and interaction of alleles and genes in a population
What are the 5 factors that influence allele frequencies sin a population
Natural selection, sexual selection, mutations, genetic drift and gene flow (mixing of new populations)
What is the hardy-weinburg equilbrium and what does it describe
p^2 + 2pq = q^2 = 1 and p + q = 1. The equilibrium describes the relationship between frequency of alleles at a locus and the genotypes resulting from these alleles
Describe the relevance of PTC in population genetics
The ability to taste PTC (bitter) is a autosomal dominant trait. Although it is theorized that selection would favour those who show phenotype (i.e. can taste) as many carcinogenic/bad foods contain PTC, studies show selection has acted to balance and maintain both tasters and non-tasters
What is the fixation index? What does an FST value of 0 and 1 mean?
The fixation index is a measure of how populations differ genetically. It measures difference sin allele freq. An FST=0 means 2 populations have no genetic difference. FST=1 means 2 populations are completely genetically different
True or False - populations that are physically closer tend to have higher FST (fixation index) values
False. Populations that a physically close tend to have similar genetic populations (due to gene flow [immigration]). Therefore the FST should be lower
1 in 2500 Australian Caucasian newborns have cystic fibrosis. C for normal is dominant over c for cystic fibrosis.
Using the hardy weinburg equilibrium please calculate the percentage of people who are carriers of CS and those who a unaffect by CS
Approximate values. Those unaffected (CC) = 0.96. Those who are carriers (Cc) = 0.04. Those who are affected (cc) = 0.0004
What are the 5 assumptions/limitations of the hardy-weinburg equilibrium
Think L.I.M.I.T.
Large population - large pop and mating must be random with respect to locus
Immigration - there must be no immigration of people with different allele frequencies
Mutations - no random mutations
Individuals of a genotypes must be able to reproduce
Traits must be mendelian (dominant or recessive)
What can cause deviations from the hardy-weinburg equilibrium
Selection, migration, mutation or assortive mating (non random mating)
What is negative selection and what is the general pattern of negative selection? Give one example of a disease that is negatively selected
Negative selection is the diminished frequency of a deleterious gene over time. In a population where p and q start of at 0.5, each generation reduces a by 1/3 (if aa is lethal). And example of a negatively selected disease is duchenne’s muscular dystrophy
What is positive selection? give an example of a disease that might be positively selected for
Positive selection is the increase in prevalence of an adaptive trait over time. An example of a gene that is positively selected for is sickle cell anaemia (immunity against malaria)
What is Genetic Drift?
• Genetic Drift is the change in the frequency of a gene variant (allele) in a population due to random sampling
What is the foudner affect? What is a consequence of the founder affect
Founder effect is the loss of genetic variation that occurs when a new population is established by a very small number of individuals from a larger population. A consequence is that mutations and genotypes of a founding member often have relatively high prevalent
