Chapter 4: Genes and Their Evolution: Population Genetics Flashcards
Heritability
Proportion of phenotype variation in a population that is due to genetic variation within individuals in the population, rather than variation in the environment conditions experienced by those individuals. Heritability varies from population to population.
Heritability Equation
H^2 = genetic variation / (genetic variation + environmental variation)
Fitness
average number of offspring from particular genotype, which causes evolutionary genetic change, based on number of children you have.
Deme
a local population that interbreeds
Gene Pool
all the genetic information in a breeding population
Reproductive Isolation
any mechanism that prevents two populations from interbreeding, could be caused by geographical distance, life habits, and chromosomal difference
Species
groups/populations/lineages of reproductively isolated organisms.
Microevolution
allele changes from generation to generation within a species/population
Macroevolution
allele/other changes involving speciation (new species development) or larger scale evolution
Equilibrium
system is stable, balanced, unchanging-evolution is a departure from equilibrium
Lactase persistence alleles
PP-lactase persistent
PR-heterozygous for lactase non-persistance-intermediate enzyme output
RR-homozygous for non-persistance
Hardy-Weinberg Equilibrium Formula
p^2+2pq+q^2=1
Hardy-Weinberg Equilibrium “If” Assumptions
- arbitrarily large population (approaching infinity)
- random mating
- all members produce same number of offspring
“Then” genotype frequencies of 1 gene remain the same after 1 generation.
Never happens but species approximate this.
Hardy-Weinberg Equilibrium “If Not” Assumptions
I. Mutation
II. Natural Selection
III. Genetic Drift
IV. Gene flow are taking place
Gene Frequencies
look at % of offspring to estimate % of p and q
Point Mutations
Mutations in the coding sequence
Synonymous Point Mutation
does not change amino acid code
Non-Synonymous Point Mutation
amino acids do change
Frameshift Mutations
insert or delete nucleotide, the three sets of codons are shifted up one or down one
Transposable Mutations
foreign invaders DNA, come from viruses, they insert into codons and throw off reading frame
Spontaneous Mutations
1 new mutation per 1000 replications
Induced Mutations
radiation and chemical mutagens, breaks Hydrogen bonds in DNA molecules, enzymes fix DNA usually incorrectly
Silent Mutations
a synonymous mutation, no change in amino acids
Missense Mutations
a non-synonymous mutation, change into another amino acid
can be caused by frameshift
Nonsense Mutations
change occurs where there is a dead stop, truncates the polypeptide coding Fram, can’t be completed
can be caused by frameshift
Klinefelter’s Syndrome
An individual has XXY the genotype of male and female t the same time
Down syndrome
Trisomy of the 21st chromosome
Pleiotropic Mutation
when genes change and affect many traits: white cat, blue eyes, deafness, timidity
Homeotic Mutation
Appearance of a body part in another place than it’s supposed to be: Fruit fly has eye appearance in wrong morphological location
Directional Selection
Favors one extreme form of a trait
ex. more children produced by people with extreme trait, selection moves that direction
Stabilizing Selection
Favors the average version of a trait
ex. humans with middle range birth weight have high chance of surviving than those with low and high birth weight
Disruptive Selection
pattern of variation is discontinuous
ex. very tall, very short people are favored
Sickle Cell and Malaria Genotype Distribution
AA- Homozygous for normal red blood cells susceptible to malaria
AS- Heterozygous for red blood cells immune to malaria
SS- Homozygous for sickle cell anemia
Balanced Polymorphism
Selection maintains two or more phenotypes for a specific gene in a population
Anthropogenic
effects caused by humans
Thalassemia
short lived red blood cells
G6PD
Glucose 6-Phosphate Dehydrogenase- lack of enzyme leads to rupturing red blood cells, or hemolytic anemia
Effective Population Size
Ne- number of organisms in a population contributing offspring to next generation
Evolution
Change in allele frequencies in populations over generations
Exogamous
Mating without or outside the group
Endogamous
Mating within a group
Dunkers
Religious group that discouraged outside marriage, very endogamous
Genetic Bottlenecks
A small portion of the population survives some catastrophe (survivors are not genetically representative of the entire population
Founder effect
a small portion of the population finds a new colony with colonist who are not genetically representative of the entire original population (accumulation of small changes in small, isolated populations)
Gene Flow
Organisms migrate into new areas, bringing their alleles with them, bringing changes
Admixture
exchange of genetic material between 2 or more populations
Exogamous Gene Flow
more gene flow, more genetic variation
Endogamous Gene Flow
less gene flow, less genetic variation
Patrilocal
males remain in birthplace; females migrate
Matrilocal
females remain in birthplace; males migrate
Summary: Mutation-, Natural selection-, Genetic Drift-, Gene Flow-,
Mutation: rise of new alleles
Natural Selection: selection favors individuals with certain phenotype
Genetic Drift: Small sampling into new population, random fluctuation
Gene Flow: organisms with genes migrate
