Natural Selection Flashcards
how is biston betularia a perfect example of natural selection?
Two forms, controlled by two alleles, melanic form prevails over typical during industrial revolution
How do you measure the relative fitness of a genotype?
Calculated by dividing by most favoured genotype, which is one
How do you measure the coefficient of relatedness?
Calculated as the difference between the fitness of the standard
(taken as 1.0) and the relative fitness of the genotype in question
Measure the reduction in fitness relative to the fittest type
What is the coefficient of relatedness?
A measure of the relative fitness of a phenotype
What happened to an allele under positive selection?
if an allele is +ve under selection, it offers a selective advantage over the other allele and as a result is increasing in frequency and replacing the other
What is positive selection
Process by which new advantageous genetic materials sweep a population, mechanism gives rise to evolution
How do rock poet mice show positive selection?
Increase in frequency of melanic forms when in an area of dark, basaltic sands, where dark forms are fitter for survival than light forms, which carry the dominant allele
HowWhat is HIV?
Human Immunodeficiency Deficiency disorder, gives rise to AIDS, almost 100% fatality
What does HIV do in the body?
Single stranded RNA virus, converts RNA into Double stranded DNA and makes an enzyme called reverse transcriptase, which is a key step in the lifecycle
How do 3TC Drugs inhibit HIV
Interferes with the normal RT, blocking the reproduction of HIV
What are the problems encountered when treating HIV?
HIV strains with mutant Its are quick to evolve, so the drug is no longer effective . Reverse transcriptase is very error prone and has high mutation rate, leading to new strains
What is sickle cell anaemia?
a recessive disorder caused by a mutation in the b haemoglobin gene, 80% die before reproduction
The S allele is responsible, but it persists at high frequencies in populations where malaria is widespread. Why?
Because heterozygote AS red blood cells don’t usually survive once infected with the disease, so die, killing the parasite with it, hence the genotype survives into reproduction. Allele is maintained at a high level due to natural selection. Displays balancing selection
What is balancing selection?
Happens when Heterozygotes are more fit than Homozygotes
