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Chapter 4: Genes and their Evolution: Population Genetics

Terms in this set (36)

deme
A local population of organisms that have similar genes, interbreed, and produce offspring. Evolution is about groups of organisms that haves the potential to reproduce.
gene pool
All the genetic information in the breeding population-all the variation within a specific genetic locus.
reproductive isolation
Any mechanism that prevents two populations from interbreeding and exchanging genetic material. If enough genetic differences accumulate, two entirely different species may emerge.
microevolution
Small-scale evolution, such as changes in allele frequency, that occurs from one generation to the next.
macroevolution
Large-scale evolution, such as a speciation event that occurs after hundreds or thousands of generations.
equilibrium
A condition in which the system is stable, balanced, and unchanging-frequencies of a population's alleles do not change over time.
Hardy-Weinberg law of equilibrium
A mathematical model in population genetics that reflects the relationship between frequencies of alleles and of genotypes; it can be used to determine whether a population is undergoing evolutionary changes.
point mutations
Replacements of a single nitrogen base with another base, which may or may not affect the amino acid for which the triplet codes.
synonymous point mutation
A neutral point mutation in which the substituted nitrogen base creates a triplet coded to produce the same amino acid as that of the original triplet.
nonsynonymous point mutation
A point mutation that creates a triplet coded to produce a different amino acid than that of the original triplet.
frameshift mutation
The change in a gene due to the insertion or deletion of one or more nitrogen bases, which causes the subsequent triplets to be rearranged and the codons to be read incorrectly during translation. Usually involves just a small part of the DNA sequence.
transposable elements
Mobile pieces of DNA that can copy themselves into entirely new areas of the chromosomes. This mutation can fundamentally alter the other gene or transpose itself on a noncoding area of the DNA sequence, causing little or no alteration.
Klinefelter's syndrome
A chromosomal trisomy in which males have an extra X chromosome, resulting in an XXY condition; affected individuals typically have reduced fertility.
spontaneous mutation
Random changes in DNA that occur during cell division which can affect only physical appearances or can have health consequences. These changes have no known cause.
induced mutations
Refers to those mutations in the DNA-caused by specific environmental agents-resulting from exposure to toxic chemicals or to radiations.
mutagens
Substances, such as toxins, chemicals, or radiation, that may induce genetic mutations.
fitness
Average number of offspring produced by parents with a particular genotype compared to the number of offspring produced by parents with another genotype.
directional selection
Selection for one allele over the other alleles, causing the allele frequencies to shift in one direction. Favors one extreme form of a trait.
stabilizing selection
Selection against the extremes of the phenotypic distribution, decreasing the genetic diversity for this trait in the population. Favors the average version of a trait.
disruptive selection
Selection for both extremes of the phenotypic distribution; may eventually lead to a speciation event.
melanic
Refers to an individual with high concentrations of melanin. Dark peppered moths had an adaptive advantage during the Industrial Revolution
nonmelanic
Refers to an individual with low concentrations of melanin. Peppered moths had an adaptive advantage before and after the Industrial Revolution.
positive selection
Process in which advantageous genetic variants quickly increase in frequency in a population.
sickle-cell anemia
A genetic blood disease in which the red blood cells become deformed and sickle-shaped, decreasing their ability to carry oxygen to tissues.
hemolytic anemias
Conditions of insufficient iron in the blood due to the destruction of red blood cells resulting from genetic blood diseases, toxins, or infectious pathogens.
abnormal hemoglobin
Hemoglobin altered so that it is less efficient in binding to and carrying oxygen.
capillaries
Small blood vessels between the terminal ends of arteries and the veins.
balanced polymorphism
Situation in which selection maintains two or more phenotypes for a specific gene in a population.
hemoglobinpathies
A group of related genetic blood disease characterized by abnormal hemoglobin.
thalassemia
A genetic blood disease in which the hemoglobin is improperly synthesized, causing the red blood cells to have a much shorter lifespan.
glucose-6-phosphate dehydrogenase (G6PD)
An enzyme that aids in the proper functioning of red blood cells; its deficiency, a genetic condition, leads to hemolytic anemia.
endogamous
Refers to a population in which individuals breed only with other members of the population.
exogamous
Refers to a population in which individuals breed only with nonmembers of their population.
founder effect
The accumulation of random genetic changes in a small population that has become isolated from the parent population due to the genetic input of only a few colonizers.
Huntington's chorea
A rare genetic disease in which the central nervous system degenerates and the individual loses control over voluntary movements, with the symptoms often appearing between ages 30 and 50.
admixture
The exchange of genetic material between two or more populations.
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