Chapter 3 Flashcards
What is population genetics?
- the branch of biology dealing with the processes that change the genetic composition of a population through time.
What is the modern synthesis?
Modern Synthesis combines the theory of inheritance with the theory of natural selection
- an explanation for the evolution of continuously varying traits that combines the theory and empirical evidence of both Mendelian genetics and Darwinism.
How can population genetics be used to understand natural selection?
- study of genetic variation within population
- emphasis on quantitive characters
- -recognizes that populations, not individuals evolve due to natural selection and genetic drift
states that frequencies of alleles and genotypes in a population remain constant from generation to generation if population is large, mating is random, no mutation, no gene flow, and no natural selection
in a population where gametes contribute randomly, allele frequencies will not change = constant frequency
How can genes alter behavior?
-• Selection can alter genes that affect beak depth, human height, and oil content. • But how can genes affect behavior? 1. Behavior is flexible 2. Individuals can adjust their behavior in response to different environmental circumstances
How can natural selection explain this? • Some insight into how behavior flexibility evolves through natural selection can be understood from the most unlikely of sources: soapberry bugs
Soapberry bugs gather in large groups near the plants they eat. • Males will mate with females to reproduce and then remain attached to prevent other males from mating with this female. • This process is called mate-guarding
By mate-guarding, a male assures
that he passes on as many of his
genes as possible, thus increasing
his reproductive success
Is there a limit to what evolution can do?
In the sense that evolution will come to a logical end and then stop, then no, there is no limit. Evolution must continue as long as there is reproduction.
But in other ways, there are limits.
Evolution is unable to respond to something a species wants or needs
It cannot eliminate traits that appear after the age of reproduction
Evolution cannot make something out of nothing,
Evolution cannot address questions not related to evolution, such as “How did the first living things arise?
Evolution cannot make a species “perfect” (
Be able to calculate gene frequencies (frequency of an allele) in a population:
- p = frequency of A; q = frequency of a
- p + q =1
- q = freq(aa) + 0.5 * freq(Aa) (here, “*” means to multiply)
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Be able to calculate genotype frequencies in a population:
- freq(aa) = q2
- freq(Aa) = 2pq
- freq(AA) = p2
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Population genetics
- the branch of biology dealing with the processes that change the genetic composition of a population through time.
Genotypic frequency
The fraction of individuals in a population that have a particular genotype.
Gene frequency
Gene frequency: the fraction of the genes at a
genetic locus that are a particular allele
Need to determine the gene frequency of the PKU allele and the “normal” allele to determine the effects of mating.
Hardy-Weinberg equilibrium
Hardy-Weinberg Equilibrium: discovered that genotypic frequencies will reach an equilibrium after just one
generation if no other forces act to change gene frequencies.
Need to know the frequencies of alleles in the population (ps and qs)
freq(aa) = q2
freq(Aa) = 2pq
freq(AA) = p
Modern synthesis
Modern Synthesis combines the theory of inheritance with the theory of natural selection
- an explanation for the evolution of continuously varying traits that combines the theory and empirical evidence of both Mendelian genetics and Darwinism.
