Exam 1 PPTs - 7 Flashcards
Genetic Drift vs. Natural Selection:
- In an ideal population of infinite size, …. favoring one allele over others will inexorably carry the favored allele to …
- If the same beneficial allele occurs in a finite population, however, … will cause the allele’s frequency to fluctuate at … around the trajectory it would have taken in a population of … size
natural selection; fixation; sampling error; random; infinite
Genetic Drift vs. Natural Selection:
- Likewise, in an infinitely large population, … favoring heterozygotes will maintain multiple alleles at … indefinitely
- in a finite population, … may cause one allele to become … and the other to be …
selection; equilibrium frequencies;
genetic drift;
fixed;
lost
Genetic Drift vs. Natural Selection:
whether drift or selection plays the predominant role in determining the evolutionary outcome will depend on both the …. and the …
size of the population;
strength of selection
Genetic Drift vs. Natural Selection:
- Stephen S. Rich and colleagues (1979) studied the interplay between natural selection and genetic drift in lab populations of the …
- Rich and colleagues took advantage of genetic variation for color at the b locus
- Beetles with genotype b+/b+ are red, beetles with genotype b+/b are brown and beetles with genotype b/b are black.
- Rich and colleagues set up 24 populations of flour beetles in which the initial frequencies of allele b+ and allele b were both …
red flour beetle;
0.5
Genetic Drift vs. Natural Selection:
- Rich and colleagues started 12 populations with … males and … females and 12 with … males and … females
50;
50;
5;
5
Genetic Drift vs. Natural Selection:
- Rich and colleagues maintained the populations at these sizes for … generations, each generation choosing adults at random to serve as … for the next gen
20;
breeders
Genetic Drift vs. Natural Selection:
- Every generation Rich and colleagues examined … … chosen individuals from each population to assess the … of the two alleles
240; randomly;
frequencies
Genetic Drift vs. Natural Selection:
- Rich’s results for the bigger population showed a pattern consistent with …
- The researchers estimated the relative fitnesses of genotypes b+/b+, b+/b, and b/b to be 1, 0.95, and 0.9
natural selection
The Neutral Theory of Molecular Evolution:
Kimura (1968, 1983)
- There are three kinds of mutations: …, … and …
deleterious;
neutral;
beneficial
The Neutral Theory of Molecular Evolution:
Kimura (1968, 1983)
- mutations that are deleterious tend to be … by natural selection
- mutations that are neutral (or nearly so) … as a result of genetic drift
- mutations that are beneficial are often … while still at low frequency, but otherwise tend to … as a result of natural selection
eliminated;
rise and fall in frequency;
lost to drift;
rise to fixation
The Neutral Theory of Molecular Evolution:
Kimura (1968, 1983)
- the study of molecular evolution began in the mid - 1960s, when biochemists succeeded in determining the … of hb, cytochrome c, and other abundant and well-studied proteins found in humans and other vertebrates
- these sequences provided the first opportunity for evolutionary biologists to compare the … and … of … among species
amino acid sequences;
amount; rate; molecular change
The Neutral Theory of Molecular Evolution:
Kimura (1968, 1983)
- Kimura took the number of sequence differences in the well-studied proteins of humans vs horses and converted them to … using divergence dates estimated from the …
rates of sequence change over time;
fossil record
The Neutral Theory of Molecular Evolution:
Kimura (1968, 1983)
- Kimura took the number of sequence differences in the well studied proteins of humans versus horses and converted them to rates of sequence change over time using divergence dates estimated from the fossil record
- For example, if the species are humans and mice, their common ancestor prob lived about 80 mya. If we look at the sequence of a 100 aa protein in the two species and it differs at 16 sites, then the rate of evolution is estimated at: …. per aa site per Ma
16/100/(80*2) is about 0.001
The Neutral Theory of Molecular Evolution:
Kimura (1968, 1983)
- Rates of molecular evolution are arguably too … for a process controlled by …
constant;
natural selection
The Neutral Theory of Molecular Evolution:
Kimura (1968, 1983)
- Kimura’s neutral theory holds that effectively … mutations that rise to fixation by … vastly outnumber … mutations that rise to fixation by …
neutral;
drift;
beneficial;
natural selection