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