test 3 Flashcards
general transcription factors
transcriptionnal control
on their own generate a low level of expression. more there are the more there is gene expression
activators
transcriptional control
proteins that bind to the promoter proximal element
cause a high transcription rate
to have a max rate of transcription, promoters can bind to the enhancer area and form a multi protein complex
gene methylation
transcriptional control
addition of a methyl group
prevents transcription factors from binding to promoter thus prevents rna polymerase II from binding and transcribing
histone tail acetylation
transcriptional control
acetylating histone tails enables rna polymerase to circulate on mRNA molecule
chromatin remodeling
transcriptional control
remodeling of chromatin to make the promoter accessible to transcription factors and activators so the transcription rate is increased
basically the loosening of the histones on the DNA strand
5’ cap
post transcriptional control
addition of 5’ cap prevents the degradation of mRNA when it travels to cytoplasm
poly a tail 1
post transcriptional control
prevents degradation of mRNA when it enters the cytoplasm
splicing
post transcriptional control
removal of the introns from mana so a complete and continuous reading frame is produced ready for ribosome to translate
splicing performed by splicosome, multi protein complex containing snRNP that are made to interact with the splice sites of mrna polymers
poly a tail 2
translational control
lente of poly a tail will modulate the translation rate of the mRNA.. between 50 and 250 nucleotide long.
longer poly a tail=higher translational rate
processing
post transnational control
polypeptide synthesized as an inactive precursor. an amino acid segment is removed from polypeptide to activate the protein’s function. thus polypeptide adopts new shape allowing it to gain full fonction
polyubiquitination
post translational control
ubiquitin tags (protein) added to protein that the cell does not want anymore.
proteasome
post translational control
multi protein complex that identifies polyubiquinated proteins, unfolds them into a polypeptide strand, cuts the polypeptide into small parts
what are the 2 principles of Lamar’s theory
- the principle of use and disuse
(body parts grow in proportion to how much they are used) - inheritance of acquired traits and the complexification of simple organisms as they move up the ladder of life
what are the 4 contributions of Lamarck theory
- he proposed that all species change through time
- recognized that changes are passed from one generation to the next
- organisms change in response to their environnements
- hypothesized the existence of specific mechanisms that caused evolutionary changes
what did Darwin come to realize with the finches
-organisms adapt to their environment
-climate and geology affects the species -> speciation
synapomorphy
ancestral trait and inferred to have been present in their most recent common ancestor
homoplasy
same characteristics but not derived from same ancestors (wings of bats and birds)
Darwin and artificial selection
-darwin was aware that traits could be selected when breeding plants or animals
-that led to him believing that nature could do the same, so natural selection
how did Darwin define natural selection
the principle by which each slight variation of a trait is preserved if useful
what is the conclusion of Darwin principle of common descent
a populations characteristics will change over the generations as advantageous, heritable characteristic become more common
what are the weaknesses of Darwins theory
-natural selection is not the only mechanism at work in evolution
-darwin did not provide the mechanism of inheritance explaining the theory (he was unaware of Mendel work)
-darwin proposed that evolution was gradual but there is often a lack of intermediary fossils
-it is still hard to explain the molecular details of reproductive isolation
what did Thomas hunt Morgan discover
genes are carried on choromosomes
what is population genetics
the recognition of the importance of genetic variation as the raw material of evolution (the frequency of alleles within a population)
what is modern synthesis
a unified theory of evolution combining biogeography, comparative morphology, comparative embryology, genetics, paleontology and taxonomy with an evolutionary framework
microevolution
small scale genetic changes that populations undergo, differences within a specie
-mutation, non random mating, gene flow, genetic drift, natural selection
-species of dogs
macroevolution
describes larger scale evolutionary changes observed in species. it results from the accumulation of microevolutionary changes and leads to speciation
-dog coyote and gray wolf
gene pool
the sum of all alleles at all gene loci in all individuals
it is like the total genetic diversityvfound within a population or a species
what does a large gene pool indicate
extensive genetic diversity
increased chances of biological fitness
a population that can survive intense selection
what does a low gene pool indicate
reduced biological fitness
increased chance of extinction
what is a mutation
-an agent of microevolutionary change
-an heritable change in dna
-it introduces a new genetic variation a population but does not change quickly allele frequency
what is gene flow
-an agent of microevolutionary change
-a change in allele frequency as individuals join a population and reproduce
-may introduce genetic variation from another population
what is genetic drift
-an agent of microevolutionary change
-a rendit change in allele frequency caused by chance events
-reduces genetic variation especially in small populations, it can eliminate rare alleles
what is natural selection
-an agent of microevolutionary change
-differential survivorship or reproduction of individuals with different phenotypes
-one allele replaces another or the allelic variation is preserved
-its the process by which characteristics for the survival of an organism increase in the following generations
-those organisms are better fit to survive, survival of the fitess
what in nonrandom mating
-an agent of microevolutionary change
-choice of mates based on their phenotypes and genotypes
-does not directly affect allele frequency but prevents genetic equilibrium
what are de novo mutations
mutations that appear in germ cells and are transmitted to every cell of the offspring. its a mutation that is not present in the parents somatic cell. the offsprings mutation can be transmitted to future generations
what are mutations
-a spontaneous and heritable change in DNA
-they are rare events
-new mutations almost never happen, they exert little to no immediate effect on allele frequency in most populations
-their number is significant over large evolutionary timescales
mutation in animals
only mutations in germ line are heritable, mutations in somatic cells have no direct effect on future generations.
mutations in plants
mutations may occur in meristem cells which eventually produce flowers as well as non reproductive structures
how do we classify mutation
based on their effect on an organism fitness
deleterious mutations
alter an individuals structure, function or behavior in harmful ways
lethal mutations
can cause great harm to organisms carrying them
neutral mutation
are neither harmful nor helpful as it will not change the amino acid because the genetic code is redundant and many codons give the same amino acid
advantageous mutation
confers some benefit on the individual that carries it
what does the hardy Weinberg model require
random mating
what makes mating non random
when a specific phenotype is preferred by most potential mates
inbreeding
special form of non random mating that involve genetically related individuals mating with one another
self fertilization
extreme example of inbreeding because an offspring is produced with the gametes of a single parent
sexual selection
other example of inbreeding, established by male competition for access to females and by the females choices of mates. produces extreme phenotypes, often seen in birds and happens when ressources are abundant and the population is healthy
genetic drift effects
dramatic effect on small populations as it violates the hardy Weinberg assumption of an infinitely large population size
-founder effect and bottleneck effect
population bottlenecks effect
foster of genetic drift
dramatic reduction in population size when a factor like flood, disease starvation, etc kill a large part of a population. it reduces genetic variation and does not always select the best alleles, goes against natural selection and survival of the fittest as the individuals survive by chance
founder effect
when only a few individuals colonize a distant locality
by chance some alleles are missing and other that were rare in a large population can be frequent in the founder group
not the same thing as consanguinity
population
group of individuals living and breeding together in the same place at the same time
specie
population of organisms capable of interbreeding and produce fertile offspring
definition does not work for organisms that can reproduce asexually
how is a new specie described
on the basis of visible anatomical characteristics
based on the morphological species concept, the idea that all individuals of a specie share measurable traits
housekeeping genes
-genes expressed in all cells
-essential for basic cellular function
-they have promoter proximal elements that are recognized by activators present in all cells
polysomes
a chain of ribosomes so they simultaneously translate the mRNA so increase the rate on transition of the mRNA chain
genes other than housekeeping genes
have promoter proximal elements recognized by specialized activators at specific times when transcription of these genes has to be activated
neo darwinism and modern synthesis
-hunt Morgan discovers that genes are carried on chromosomes which links Mendel’s and Darwin’s work
-modern synthesis combines data from biogeography, comparative morphology, comparative embryology, genetics, paleontology and taxonomy with an evolutionary framework
-neo darwinism acknowledge other evolutionary patterns like micro/macro evolution
why is diversity important in a gene pool
because it indicates an increased chance of biological fitness, associated with robust populations that can survive periods of intensive selection.
low genetic diversity in a gene pool can cause reduced fitness and increase the chance of extinction. but this could be positive as there could be genetic drift and new genetic variants that increase the fitness, which are more likely to fix in small populations
hardy Weinberg equation
p+q=1 -> allele frequency
p^2+2pq+q^2=1 ->genotype frequency
if both laws are respected in a population, the population is not evolving
will remain constant from gen to gen in the absence of evolutionnary influences
p / q
p dominant allele
q recessive allele
genetic equilibrium is reached when
-no mutations are occurring
-there are no migrations coming into the population (no gene flow)
-pop is infinite in size
-all genotypes in the pop survive and reproduce equally (no nat sel)
-individuals mate randomly (no mate choice)
what are the mech of micro evolution
mutation
gene flow
genetic drift
natural selection
nonrandom mating
relative fitness
relative fitness=
absolute fitness/average fitness
absolute= number of offspring of the individual
average=average number of offspring of individuals in population
to evaluate the reproductive success
what are the three modes of natural selection
directional selection
stabilizing selection
disruptive selection
how are the effects of natural selection measured
by recording changes in the mean and variability of characters over time
when do traits undergo directional selection
when individuals near one end of the phenotypic spectrum have the highest relative fitness
most cases of artificial selection are directional selection
when to individuals undergo stabilizing selection
when individuals expressing intermediate phenotypes have the highest relative fitness, stabilizing selection eliminates extreme phenotypic extremes and reducing genotypic and phenotypic variations
most common type
when does disruptive selection happen
when extreme phenotypes have a higher relative fitness than intermediate phenotypes, then alleles with extreme phenotypes become more common promoting polymorphism, it is much less common than 2 other types
population
a group of individuals, living and breeding together In the same place at the same type
how does sexual selection lead to extreme phenotypes
when there is competition for the access to females and by the females choices of mate, usually happen when ressources are abundant and the population is healthy
species
working definition of species depends on the organisms to which it is applied
ex the definition a species is a population of organisms capable of interbreeding and producing a fertile offspring does not work with asexual organisms
how are new species described
on the basis of visible anatomical characteristics, based on the morphological species concept which is the idea that all individuals of a species share measurable traits that distinguish them from other species
limits of morphological concept
it does not help us distinguish closely related species that are almost identical in appearance
what is the biological species concept
it emphasizes the dynamic nature of species
-if the members of two populations interbreed and produce fertile offspring they are In the same species
-if two population do not interbreed in nature or fail to produce fertile offspring they belong to different species
advantages of biological concept
-defines species in terms of population genetics and evolutionnary theory in a static world
-considers the gene flow that pop of same species experience
-emphasizes the genetic distinctivness of each species
limits of biological concept
does not apply to populations that reproduce asexually
does not take into account that some different species can breed together and produce fertile offspring ex homo sapiens and homo neandertalis
what is phylogenetic concept based on
it uses both morphological and genetic sequence data to construct an evolutionnary tree
scientists define a phylogenetic species as a cluster of populations
advantages of phylogenetic concept
applies to any group of organisms including species that are extinct and some that reproduce asexually
approach also argues that the morphological and genetic distinctions between organisms on different branches of the tree of life represent the absence of gene flow
what are the pre zygotic isolating mechanisms (premating)
ecological isolation
temporal isolation
behavioral isolation
mechanical isolation
gametic isolation
what are the post zygotic mechanisms (post mating)
hybrid inviability
hybrid sterility
hybrid breakdown
ecological isolation
species live in different ecological locations so do not meet
ex polar bear and grizzlies
or marine and terrestrial iguanas
temporal isolation
species that breed in different seasons can’t breed with one another
ex American and fowlers toads
behavioral iso
some species harbor and elaborate courtship in mating season and those behaviours are often not recognized by other species
ex:courting dance or pointing display
mechanical iso
differences In structure color or scent inhibit species from breeding with one another
ex purple monkey flower and scarlet monkey flower grow next to one another and pollinators only visit one of the two
gametic iso
incompatibility between the sperm of one species and the eggs of another,
ex marine invertabrates release gametes Into the environnement for external fertilization
hybrid inviability
hybrids can have two sets of developmental instructions which may not interact properly with one another and the embryo might die early as a result
ex the lipid is sterile and has very short lifespan
hybrid sterility
hybrid between closely related species might develop well, they may not produce functional gametes so they have zero fitness
ex: a mule, cross of a female horse and male donkey
hybrid breakdown
the second generation from 2 hybrids may experience reduced survival or fertility
