Human Evolution (Ch. 4)

Abnormal Hemoglobin

Hemoglobin altered so that it is less efficient in binding to and carrying oxygen.

Admixture

The exchange of genetic material between two or more populations.

Anthropogenic

Relating to any effect caused by humans.

Balanced Polymorphism

A 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 other alleles, causing allele frequencies to shift in one direction.

Disruptive Selection

Selection for both extremes of a phenotypic distribution; may eventually lead to a speciation event.

Endogamous

Characterized by endogamy, which is the practice (by a population or group) of breeding only within the population.

Equilibrium

A condition in which a system is stable, balanced, and unchanging.

Exogamous

Characterized by exogamy, which is the practice (by a population or group) of breeding outside the 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

A 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 a breeding population.

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.

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.

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.

Induced Mutations

Mutations in DNA resulting from exposure to toxic chemicals or to radiation.

Introgression

Gene flow from closely related groups that were formerly reproductively isolated.

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.

Nonsynonymous Point Mutation

A point mutation that creates a triplet coded to produce a different amino acid from 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

The process by which advantageous genetic variants quickly increase in frequency in a population.

Reproductive Isolation

Any circumstance that prevents two populations from interbreeding and exchanging genetic material, such as when two populations are separated by a large body of water or a major mountain range.

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 Mutations

Random changes in DNA that occur during cell division.

Stabilizing Selection

Selection against the extremes of a phenotypic distribution, decreasing the genetic diversity for a trait in the population.

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.

Thalassemia

A genetic blood disease in which hemoglobin is improperly synthesized, causing red blood cells to have a much shorter life span.

Transposable Elements

Mobile pieces of DNA that can copy themselves into entirely new areas of chromosomes.