86 terms

BIEB 150 Midterm 1

Lecture 7

Terms in this set (...)

disadvantages of sex
I.) The breakup of advantageous genotypes.
II.) A twofold disadvantage to sex.
III.) Horizontally transmitted sexual diseases.
advantages of sex
I.) The Ability to Repair DNA Damage.
II.) May Be Advantageous in a Temporally Diverse Environment
III.) Can Be Advantageous if Pathogens Make the Future Unpredictable- Red Queen Races and Arms Races
Red Queen
a series of evolutionary responses to continual changes in the physical or biological environment that maintain fitness but that do not result in large changes in gene function
Arms Races
organisms adapt to a series of large changes in their predators or pathogens by evolving new types of attack and defense.
(genetics) modification of a cell or bacterium by the uptake and incorporation of exogenous DNA
(genetics) the process of transfering genetic material from one cell to another by a plasmid or bacteriophage
A temporary union of two organisms for the purpose of DNA transfer.
alleles, which are so divergent that they do not appear to have had a common ancestor
(biology) reproduction by the union or fusion of games of the same size and structure
fusion of two dissimilar gametes, still physically similar, sizes different
horizontal gene transfer
the process by which genes are transferred between species by
plasmids, transposons, retrotransposons and retroviruses.
-i.e. adaptive immune system
RAG1 and RAG2
-what proteins are required for VDJ recombination of Ab
-bind to short stretches of DNA called recognition signals that are found adjacent to the gene fragments of the immunoglobulin genes. The RAG proteins loop the DNA to bring these signal regions close together
transient polymorphism
if one allele is gradually replacing the other then a population will show transient polymorphism
mechanisms that maintain balanced polymorphism
1.) mutation-selection balance
2.) heterozygote advantage
3.) spatial environmental heterogeneity
4.) Temporal environmental heterogeneity
5.) Negative frequency-dependent selection
6) Gene flow
heterozygote advantage
-greater reproductive success of heterozygous individuals compared to homozygotes
-tends to preserve variation in gene pools
-q = s1/(s1+s2)
spatial environmental heterogeneity
the environment is different in different parts of the geographic range of a species
temporal environmental heterogeneity
the dispersement of species differs by time
phase polymorphisms
i.e. snowshoe hare Lepus americanus change from a brown summer coat to a white winter coat
frequency-dependent selection
a decline in the reproductive success of individuals that have a phenotype that has become too common in a population
Disruptive Selection
form of natural selection in which a single curve splits into two; occurs when individuals at the upper and lower ends of a distribution curve have higher fitness than individuals near the middle
Stabilizing selection
-natural selection that favors intermediate variants by acting against extreme phenotypes
-p. dardanus
founder effects
a particular form of genetic drift deriving from a small founding population not possessing all the alleles present in the original population
size bottlenecks
form of genetic drift in which a population becomes extremely small; may lead to differences in allele frequencies and a loss in genetic variability
population of microorganisms (and their genetic material) that live on or in the human body
random assortment and genetic recombination
-shuffle all this variability into new combinations as a result of meiosis and the production of gametes, is a fifth and extremely powerful evolutionary process
-extremely powerful evolutionary process
linkage equilibrium
-gABgab = gAbgaB
-Occurs when the genotype present at one locus is independent of the genotype at a second locus.
linkage disequilibrium
-D = f(AB).f(ab) - f(Ab).f(aB)
-tendency for certain alleles at 2 linked loci to occur together more often than expected by chance.
genetic hitchhiking
when a neutral or slightly negative allele experiences positive selection because it is close to an advantageous allele on the chromosome
Inbreeding Coefficient
-the probability that at a given locus an individual has two copies of an allele that are identical by descent
crossing to unrelated individuals
identity by descent
the two alleles the individual carries had a common ancestor so recently that copies of the ancestral gene have come down unchanged through the intervening generations
identity by state
two different alleles happen by chance to have converged by separate pathways of mutational change so that they are now identical
inbred fraction
F(p + q) = F
outbred fraction
(1 - F) (p^2 + 2pq + q^2) = (1 - F)
inbreeding depression
the harmful effects of inbreeding on
ability to pass genes to the next generation
darwinian fitness
-the relative probability that an organism will survive and reproduce,
compared with the average for all the members of the population
factors that contribute to an organism's w value
survival to reproductive age, ability to find mates, fertility and fecundity
intraspecific competitive ability
the ability to compete with other members of the same species for
interspecific competitive ability
the ability to compete with other species for resource
batesian mimicry
A type of mimicry in which a harmless species looks like a species that is poisonous or otherwise harmful to predators.
müllerian mimicry
When harmful species converge on such an aposematic signal (obviously warning signal)
the number of progeny produced by that individual during a unit of time such as a year
reproductive value
the numbers of progeny that the individuals will contribute to the population at a given point in time in the future, adjusted for changes in population size
directional selection
Form of natural selection in which the entire curve moves; occurs when individuals at one end of a distribution curve have higher fitness than individuals in the middle or at the other end of the curve.
stabilizing selection
Natural selection that favors intermediate variants by acting against extreme phenotypes.
new varieties of organisms showing large differences from the original species can occasionally appear
-hypotheses about the evolutionary histories of organisms that represent our best guesses about how evolution happened
-depend on the measurement of characters of organisms
character that is shared by two species was derived from a common ancestor
-arisen independently in the two evolutionary lineages through evolution from dissimilar ancestors
A homoplasy is a character shared by a set of species but not present in their common ancestor.
terminal (external) nodes
tips of the branches of the tree
a group consisting of an ancestor and all its descendants, a single "branch" on the "tree of life"
internal node
represent the points of divergence where two different branches of evolution arose
The root of a tree is the node that represents the common ancestor of all taxa in the tree.
shared primitive character
character that is shared by all the members of this clade
shared derived character
a trait that evolved in the ancestor of a group and is present in all its descendants (though it may be lost or modified secondarily
taxon (group of organisms) which forms a clade, meaning that it consists of an ancestral species and all its descendants
made up of more than one clade
maximum parsimony
-explanation for a phenomenon should not involve unnecessary steps
- character-based method that infers a phylogenetic tree by minimizing the total number of evolutionary steps required
primate slowdown
-it appears that the molecular clock has run at a slower rate in the primate lineage than in the ungulate and marsupial lineages
-may have taken place because primate generation times are long
compared with those of other mammals. Mutation rates are lower in long-generation animals
maximum-likelihood analysis
starts with a model of change and then looks at many trees to determine which of the trees best fits the model
horizontal gene transfer
Transfer of genes between species, often but not always prokaryotes, through mechanisms such as plasmids, transposons, retrotransposons, and retroviruses.
gene mutations
small changes in DNA molecules, affect single genes
chromosomal mutations
include shufflings of the order of genes on chromosomes and the gain or loss of entire chromosomes
mobile elements
can move among the chromosomes, from cell to cell, and even from one species to another through the process of horizontal gene transfer
any change in the genetic material that results in an alteration of the sequence of bases
crossovers and mutation
-important kind of alteration to the genetic material, however, should not usually be considered a mutation.
-crossovers between homologous chromosomes, which take place during Meiosis I and can sometimes take place during mitosis, usually simply shuffle the genetic material on the
maternal and paternal chromosomes and do not make any changes to the DNA of the alleles
allele or organism that is the result of the mutational change
somatic or germ-line mutations
Somatic mutations can occur in any of the cells of the body except the germ cells (sperm and egg) and therefore are not passed on to children. Only the latter, which make up a small fraction of all mutations, are heritable
epigenetic changes
- literally means "above" or "on top of" genetics
-these modifications do not change the DNA sequence, but instead, they affect how cells "read" genes (i.e. methylation)
harmful mutant alleles
q = sqrt(μ/s) (since p is close to 1)
s : represents the disadvantage conferred by the allele
steady state mutation
q = μ/(μ +ν)
μ : forward mutation rate
v : reverse mutation rate
Highly repetitive gene sequences that don't code for polypeptides, several thousand sequential copies at many points in the genome
replica plating
A method of identifying bacterial colonies that have certain mutations by transferring cells from each colony on a master plate to a second (replica) plate and observing their growth when exposed to different conditions.
germ-line mutations
Mutations that occur in cells that will give rise to gametes, which gives them a chance to be passed on to the next generation
somatic mutations
they occur in other cells in the body (soma in Greek) that will not give rise to gametes.
- Any trait that has two or more alleles that occur at appreciable frequencies, at a given genetic locus
transient polymorphism
If one allele is gradually replacing the other then a population will show transient polymorphism
balanced polymorphism
The ability of natural selection to maintain diversity in a population.
transposable (mobile) elements
Segment of DNA that can move from one site to another site on the same or different DNA molecules
-viral, transposons, retrotransposons
(jumping genes) short strands of DNA capable of moving from one location to another within a cell's genetic material
Transposable elements that move within a genome by means of an RNA intermediate, a transcript of the retrotransposon DNA.
-uses reverse transcriptase
Movement of transposons is catalyzed by this enzyme, specific for their respective elements
Hardy-Weinberg equilibrium
Condition that occurs when the frequency of alleles in a particular gene pool remain constant over time
Hardy-Weinberg equilibrium
p^2RR + 2pqRr + q^2rr