Studied by 2 peoplemicroevolution
change in allele frequencies in a population over generations
genetic variation
caused by differences in genes or other DNA segments among individuals
phenotype
product of inherited genotype and environmental influences
introns
noncoding regions where most differences occur; 90% of the human genome
exons
coding regions that rarely change the amino acid sequence of the encoded protein; 10% of the human genome
mutation
a change in the nucleotide sequence of DNA
point mutation
change in a single nucleotide in a DNA sequence
Hardy-Weinberg equation
illustrates the genetic makeup one predicts for a population that is not evolving at a locus
neutral variation
variation showing no selective advantage or disadvantage
gene pool
aggregate of all copies of every type of allele at all loci in every individual in a population
population
localized group of individuals capable of interbreeding and producing fertile offspring
incomplete dominance
an inheritance pattern in which the heterozygous trait is a mix of the homozygous dominant and homozygous recessive traits
Hardy-Weinberg equilibrium
a population where gametes contribute to the next generation randomly and Mendelian inheritance occurs; allele and genotype frequencies remain constant from generation to generation
Punnet Square
the way to confirm the frequency of genotypes without using an equation
phenylketonuria (PKU)
genetic disorder of a locus being in Hardy-Weinberg equilibrium
adaptive evolution
process in which traits that enhance survival or reproduction increase in frequency over time
genetic drift
describes how allele frequencies fluctuate unpredictably from one generation to the next; most pronounced in small populations; tends to reduce genetic variation through random loss of alleles
Founder effect
genetic drift that occurs when a few individuals become isolated from a larger population and form a new population whose gene pool composition is not reflective of that of the original population
Bottleneck effect
when there is a major change in the gene pool due to a significant reduction in the population from human action or a disaster/change in environment
gene flow
the transfer of alleles from one population to another, resulting from the movement of fertile individuals or their gametes
relative fitness
the contribution an individual makes to the gene pool of the next generation relative to the contributions of other individuals
directional selection
favors individuals at one extreme end of the phenotypic range
disruptive selection
favors individuals at both extremes of the phenotypic range
stabilizing selection
favors intermediate variants and acts against extreme phenotypes
sexual dimorphism
marked differences between the sexes in secondary sexual characteristics
intra-sexual selection
direct competition among individuals of one sex (often males) for mates of the opposite sex
inter-sexual selection
occurs when individuals of one sex (usually females) are choosy in selecting their mates; mate choice
good genes hypothesis
suggests that if a trait is related to male genetic quality, both the male trait and female preference for that trait should
balancing selection
occurs when natural selection maintains stable frequencies of two or more phenotypic forms in a population
frequency-dependent selection
the fitness of a phenotype depends on how common it is in the population
heterozygote advantage
occurs when heterozygotes have a higher fitness than either homozygotes
sexual selection
Process in which individuals with certain inherited characteristics are more likely to acquire mates than other individuals of the same sex
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