ATR 250
Chapter 4: Genes and Their Evolution- Population Genetics

admixture    The exchange of genetic material  between two or more populations. 
balanced polymorphism    Situation in which selection maintains two or more phenotypes for a specific gene in 
	a population. 
capillaries    Small blood vessels between the terminal ends of arteries and the veins.
deme    A local population of organisms that have similar genes, interbreed, and produce offspring.
directional selection Selection for one allele over the other alleles, causing the allele frequencies to shift in one    
      direction.	
disruptive selection Selection for both extremes of the phenotypic distribution; may eventually lead to a speciation
event.
endogamous    Refers to a population in which individuals breed only with other members of the population.
equilibrium   A condition in which the system is stable, balanced, and unchanging.
exogamous    Refers to a population in which individuals breed only with nonmembers of their population.
 fitness    Average number of offspring produced by parents with a particular genotype compared to the number of offspring produced by parents with another genotype.
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.
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.
gene pool- All the genetic information in the breeding population.
hemoglobinopathies    A group of related genetic blood diseases characterized by abnormal hemoglobin.
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.
induced mutations Refers to those mutations in the DNA resulting from exposure to toxic chemicals or to 
radiation
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.
macroevolution    Large-scale evolution, such as a speciation event, that occurs after hundreds or thousands 
of generations.
microevolution    Small-scale evolution, such as changes in allele frequency, that occurs from one 
generation to the next.
mutagens    Substances, such as toxins, chemicals, or radiation, that may induce genetic mutations. 
nonmelanic    Refers to an individual with low concentrations of melanin.
nonsynonymous point mutation A point mutation that creates a triplet coded to produce a different amino
acid than that of the original triplet.
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
 positive selection    Process in which advantageous genetic variants quickly increase in frequency in a population.
reproductive isolation    Any mechanism that prevents two populations from interbreeding and exchanging genetic
material.
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.
spontaneous mutation Random changes in DNA that occur during cell division.
stabilizing   selection Selection against the extremes of the phenotypic distribution, decreasing the genetic diversity 
for this trait in the population.
transposable elements Mobile pieces of DNA that can copy themselves into entirely new areas of the
chromosomes.