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Biological Anthropology: Chapter 4

Terms in this set (47)

deme
a local population of organisms that have similar genes, interbreed, and produce offspring
gene pool
all the genetic information in the breeding 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
EX: emus (Australia) & ostriches (Africa)
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
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
Hardy-Weinberg law of equilibrium (2)
What might cause a population to change its allele frequencies and go out of equilibrium?
Genes are passed from generation to generation by interbreeding within populations in particular and among members of the species in general, and genetic changes result from one or a combination of the four forces of evolution: mutation, natural selection, genetic drift, and gene flow
Mutations
are the only source of new genetic variation in a population (in the absence of gene flow)
base substitutions
a type of DNA mutation that occurs when a single nitrogen base is substituted by another base
base insertions
a type of DNA mutation that occurs when a nitrogen base is added to the DNA template
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
-i.e., incorrect base pairing
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
-same amino acid, therefore no response occurs
nonsynonymous point mutation
a point mutation that creates a triplet coded to produce a different amino acid from that of the original triplet
-can have dramatic results
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
-protein w/o function
-small part of DNA sequence
transposable elements
mobile pieces of DNA that can copy themselves into entirely new areas of the chromosomes
trisomy
an extreme mutation where entire chromosomes can be duplicated
i.e., Down's syndrome (extra chromosome 21)
monosomy
an extreme mutation where entire chromosomes are lost altogether
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
-47 chromosomes
-extra breast tissue
-range of physical effects
spontaneous mutations
random changes in DNA that occur during cell division
-no known cause
induced mutations
mutations in the DNA resulting from exposure to toxic chemicals or to radiation
-usually associated with human activity
"agents": mutagens
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
-human evolution has favored large brains
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 the trait
disruptive selection
selection for extremes of the phenotypic distribution; may eventually lead to a speciation event
melanic
refers to an individual with high concentrations of melanin
-black moth
nonmelanic
refers to an individual with low concentrations of melanin
-white moth
G6pd gene
Glucose-6-Phosphate Dehydrogenase
an enzyme that aids in the proper functioning of red blood cells; its deficiency, a genetic condition, leads to hemolytic anemia
- one target of natural selection in humans is this gene, located on the X chromosome
positive selection
process in which advantageous genetic variants quickly increase in frequency in a population
EX: moths in English industrial revolution that changed from black to white, ensuring survival
sickle-cell anemia
a genetic blood disease in which the red blood cells become deformed an sickle-shaped, decreasing their ability to carry oxygen to tissues
-hemoglobin S gene
-simple pair-base mutation
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 is altered so that it is less efficient in binding to and carrying oxygen
Malaria (notes)
- Many people living in equatorial Africa had S-gene, counter-intuitive for there should be strong selection against non-beneficial gene.
- Discovered AS frequencies appear where malaria is endemic in high carrier populations.
- AS carriers either don't contract malaria or suffer less severe infection.
- AA: normal hemoglobin
- SS: homozygous for sickle-cell
- AS: heterozygous carriers, poor hosts for malarial parasites
Malaria (definition)
potentially lethal parasitic infection in which the parasite is introduced to a human host by a mosquito
balanced polymorphism
situation in which selection maintains two or more phenotypes for a specific gene in a population
EX: sickle-cell anemia
anthropogenic
refers to any effect caused by humans
hemoglobinopathies
a group of related genetic blood diseases 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 life span
endogamous
refers to a population in which individuals breed only with other members of the population
- Dunkers
- Australian aborigines
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
- a form of genetic drift
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
- example of Founder effect
admixture
(also gene flow)
the exchange of genetic material between two or more populations
demic diffusion
a population's movement into an area previously uninhabited by that group
What causes evolution?
1) Mutation: heritable change in structure or amount of DNA
-- Sickle-cell, Huntington's, Klinefelter's, Down syndrome
2) Natural selection: favoring of individuals with characteristics that enhance survival and reproduction
-- Sickle cell, industrial melanism, thalassemia, G6PD, Lactase deficiency
3) Genetic drift: genetic change due to chance
-- Klinefelter's, blood types, hemophilia
4) Gene flow: transfer of genes across population boundaries
-- Blood types
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