Test 3 Flashcards
1
Q
5 mechanisms of transcriptional control
A
- general transcription factors
- activators
- methylation
- histone tail acetylation
- chromatin remodelling
2
Q
what are general transcription factors and what do they do?
A
generate a low level of expression on their own. The more there are, the higher the expression of the gene.
3
Q
activators
A
- proteins that bind to the promoter proximal elements and bring a high transcription rate
- others can bind to the enhancer region and form a multi-protein complex with activators at the promoter proximal elements, which brings the maximum rate of expression
4
Q
methylation
A
- DNA methylation enzymes add a methyl group to bases of DNA.
- Methylated bases in promoter regions can prevent the binding of transcription factors, turning the gene off
5
Q
histone tail acetylation
A
- changes the charge on the histone tails and results in a loosening of the association of the histones with DNA
6
Q
chromatin remodelling
A
- chromatin can be remodelled to make the promoter accessible to transcription factors and activators, increasing the transcription rate
7
Q
3 mechanisms of post transcriptional control
A
- caping: 5’ cap and poly-a tail
- alternative splicing
8
Q
5’ cap
A
- added to 5’ end of mRNA
- protects it from degradation and is the site where ribosomes attach at the start of translation
9
Q
poly-A tail
A
the tail prevents mRNA from degradation when they enter the cytoplasm
10
Q
alternative splicing
A
- introns removed by spliceosomes
- spliceosomes cleave the pre-mRNA at the junction between the 3’ and 5’ end of intron.
- intron loops back on itself ans is cleaved
- only exons left (introns = non protein coding segments)
11
Q
mechanism of translational control
A
adjusting the length of the poly-a tail
12
Q
adjusting length of poly a tail
A
- enzymes change the length of the tail
- increased length = increased translation
- decreased length = decreased translation
13
Q
3 mechanisms of post translational control
A
- processing (protein activation)
- polyubiquitination (protein degradation)
- proteasome (protein degradation)
14
Q
processing
A
- proteins are synthesized as inactive precursors, which are converted to an active form under regulatory control.
- protein activation
15
Q
polyubiquitination
A
- short lived proteins are marked for breakdown by enzymes that attach to a doom tag which is called ubiquitin.
- the tag labels the unnecessary or damaged proteins that need to be destroyed.
- addition of ubiquitin to a protein
16
Q
proteasome
A
- proteasomes recognize doom tags and attack the protein to break it down
- proteasome = large cytoplasmic complex of different proteins.
17
Q
why are eukaryotic gene expression more complicated than prokaryotic?
A
- more complex cells (organelles, different proteins that need to be coded for)
- nuclear DNA is organized in histones (tightly packed DNA) into chromatin
- multicellular eukaryotes produce large numbers and different types of cells
18
Q
what are promoter proximal elements?
A
regulatory sequences farther upstream that may stimulate or inhibit the rate of transcription initiation
19
Q
where do general transcription factors bind?
A
to promoter in TATA box
20
Q
what are housekeeping genes?
A
genes that are expressed in all cell types for basic cellular functions (ex: glucose metabolism)
21
Q
what is an advantage that eukaryotes have on prokaryotes?
A
exon shuffling = protein diversity (but can also lead to disorders)
22
Q
what are the 3 disciplines of evolution?
A
biogeography
comparative morphology
geology
23
Q
biogeography
A
study of geographic distribution of plants, animals and other forms of life
24
Q
what is comparative morphology
A
comparing the morphology of species to understand and discover common ancestors
25
what is geology?
- Georges Cuvier discovered layers of fossils
- abrupt changes between geological layers markes dramatic shifts in ancient environments
- catastrophism : each layer of fossils represent the remains of organisms that had died in a local catastrophe
26
what was Lamarck's theory?
- proposed that a metaphysical perfecting principle caused organisms to become better suited to their environments.
- transmission of traits acquired within an organism's lifetime
27
what are the 2 principles of Lamarckism?
- use and disuse: body parts grow in proportion to how much they are used. unused parts get weaker and shrink
- changes are passed from one generation to the next, making the organisms of today evolved
28
how did Lamarck contribute to the development of evolutionary worldviews?
- proposed that all species change through time
- recognized that changes are passed from generation to the next
- organisms change in response to their envionment
- hypothesized the existence of mechanisms that cuase evolutionnary change
29
what is one of darwin's principles?
principle of common descent
30
what is the principle of common descent?
observing different species that look the same or have things in common to understand that they all may come from the same place but all adapted differently to their environment
31
what does synapomorphy mean?
a trait that is ancestral and inferred to have been present in their most recent common ancestor.
32
what does homplasy mean?
same trait but not common ancestor
33
what is artificial selection?
traits are selected when breeding plants or animals
34
what is fitness?
organisms with characteristics that help them are better able to survive and can reproduce in greater numbers.
35
what is population genetics?
a new discipline that recognizes the importance of genetic variations as the raw material of evolution (frequency of alleles within a population)
36
what is modern synthesis or neodarwinism?
- a theory of evolution
- integrated data from biogegrophy, comparative morphology, genetics, taxonomy, etc
37
what are the 3 primary mechanisms of evolution?
- natural selection
- neodarwinism (modern synthesis)
38
what does modern synthesis acknowledge that natural selection doesn't?
how genes are inhertited, microevolution and macroevolution
39
what is microevolution?
- small-scale genetic changes that populations undergo
- same species with some small differences
- any change of allele frequency within a population
- ex: different breeds of dogs
40
what is macroevolution?
- larger-scale evolutionary changes
- gradual accumulation of microevolutionary changes
- distinct species
- ex: dog, grey wolf, coyote
41
what did Darwin propose that Lamarck didn't?
fitness: organisms with beneficial characteristics are better able to survive and reproduce
42
what is the main concept in neodarwinism that added to natural selection?
how genes are inherited from parent to offspring
43
what are the processes (adding to natural selection) that modern synthesis accounts for?
micro and macro evolution
44
what is a gene pool?
- sum of all alleles of all individuals in a population
- total genetic diversity found within a population or species
45
what does a large gene pool indicate and why is it good?
- extensive genetic diversity
- increased change of biological fitness
- if more fitness, population is more robust abd can survive intense selection
46
what does a low gene pool indicate and why is it bad?
- reduced biological fitness
- increased chance of extinction
47
what are the 5 mechanisms of microevolution?
- natural selection,
- mutation
- nonrandom mating
- genetic drift
- gene flow
48
what are mutations?
- spontaneous and heritable change in DNA
- can be passed on to offspring
49
what are the types of mutations?
- deleterious
- lethal
- neutral
- advantageous
50
what are deleterious mutations?
- alter an individual's structure, function, behavior in harmful ways
51
what are lethal mutations?
- cause great harm to individual
52
what are neutral mutations?
not harmful nor helpful
53
what are advantageous mutations?
- benefit the individual
- might become more frequent with time because of natural selection
54
what is nonrandom mating?
selecting a mate with a particular phenotype (preferred by most potential mates)
55
what is inbreeding?
genetically related individuals mating with each other
56
what is self-fertilization?
offspring produced from the gametes of a single parent
57
what is an example of nonrandom mating?
sexual selection: male competition for access to females
- produces extreme phenotypes (because the chosen males have extreme phenotypes) and usually happens when population is healthy
58
what is gene flow?
- the glue that keeps populations of the same species together
- organisms or their genetic material moving from one population to another
- introduce new alleles in a population
ex: oak's accorns are carried by blue jays from one population to another
59
what is genetic drift?
- chance events cause the allele frequencies in a population to change unpredictably and randomly
60
what are the circumstances that foster genetic drift?
bottleneck effect and founder effect
61
what is the bottleneck effect?
- stressful factor (disease, starvation, etc) produce a dramatic reduction in population size
- greatly reduces genetic variation, even if it rebuilds
- alleles survivre only by chance
62
how is genetic drift different from natural selection?
- it is a good example of how evolution does not always select the best alleles (natural selection), because it sometimes is random
- choice of alleles in natural selection is done according to the most fit, but genetic drift allele choice is random
63
what is the founder effect?
- individuals colonize a distant locality and start a new population, they only carry a small sample of the population's genetic diversity
- some alleles might be missing or highly present, only due to chance.
64
what is an example of genetic drift?
the french canadian population : created by 8500 colonists but only 4000 contributed to gene pool
65
what is natural selection?
- process by which advantageous traits become more common in subsequent generations
- characteristics that better enable an organism to adapt will increase
- nature selects the phenotype, not the genotype, so if hetero, both alleles are passed on
66
what is relative fitness?
- the number of surviving offspring that an individual produces compared with the numbers left by other populations
- goal: evaluate reproductive success
67
how to calculate relative fitness?
absolute fitness of the individual/ relative fitness (population average)
68
what are the three modes of natural selection?
- directional selection
- stabilizing selection
- disruptive selection
69
what is directional selection?
- individuals near one end of the phenotypic spectrum have the highest relative fitness
- shifts the mean phenotype toward the end of the distribution favored by natural selection
70
what does the curve of directional selection look like?
the curve completely shifts to the right or left
71
what is stabilizing selection?
- individuals with intermediate phenotypes have the highest relative fitness
- eliminating phenotypic extremes = reduces genetic and phenotypic variation
72
what does the curve of stabilizing selection look like?
is becomes high in the middle and narrow
73
what is disruptive selection?
- extreme phenotypes have higher relative fitness
- extreme phenotypes become more common = polymorphism
74
what does the curve of disruptive selection look like?
becomes 2 curves with not a lot in middle a more on extremities
75
what is the hardy weinberg equilibrium?
allele and genotype frequencies in a population will remain constant from generation to generation in the absence of evolutionary influences (no mechanisms at play)
76
what are the equations for equilibrium?
p+q=1
p^2 + 2pq + q^2 = 1
77
what does it mean if the calculated allele frequencies match the expected from the equation?
it means the population is at equilibrium, it is not evolving.
but if it doesn't fit, you can't say it's evolving
78
what do the variables represent in the equations?
the frequencies of each allele
79
what is the morphological concept of species?
- all individuals from a same species share measurable (visible) traits that distinguish them from other individuals of other species.
- if they look the same, they are the same
80
what are the advantages of the morphological concept?
- to identify fossils
- easy to recognize them, only need to use the physical characteristics
81
what are the limits of the morphological concept?
- some are different because of their conditions even though they are the same species
- tell us little about evolutionary processes
- does not help distinguish species that look very much alike
82
what is the biological concept of species?
- if the members of two populations interbreed and produce fertile offspring (naturaly), they are the same
83
what are the advantages of the biological concept of species?
- defines species in terms of population genetics and evolutionary theory
- Take gene flow into account (as long as there is gene flow, same species)
- emphasizes the genetic distinctness of species
84
what are the limits of thebiological concept of species?
- does not apply to forms of life that reproduce asexually
- there are exceptions (divergent species can sometimes still breed)
85
what is the phylogenetic concept of species?
- comparing DNA % similarity
- using biological and morphological concepts
86
what are the advantages of the phylogenetic concept of species?
- applies to any group of organisms
- absence of gene flow (reproductive isolation)
87
what are the prezygotic isolating mechanisms?
- ecological isolation
- temporal isolation
- behavioral isolation
- mechanical isolation
- gametic isolation
88
what is ecological isolation?
- species live in different ecological location, so they dont meet.
- ex: polar bears and grizzlies
89
what is temporal isolation?
- species breed in different seasons, so cannot breed together
- not ready to mate at the same time
90
what is behavioral isolation?
- some species have elaborate courtship that other species dont understand, so they don't mate
- different ways to mate
91
what is mechanical isolation?
- difference in structure, shape, scent, which prevents from breeding.
92
what is gametic isolation?
- incompatibility between the sperm of one species and the eggs of another
93
what are the postzygotic isolating mechanisms?
- hybrid inviability
- hybrid sterility
- hybrid breakdown
94
what is hybrid inviability?
- hybrid organisms (from 2 species) often die as embryos or at a young age
95
what is hybrid sterility?
- the hybrid may grow and be normal, but cannot produce functional gametes
- cannot reproduce = zero fitness
96
what is hybrid breakdown?
- first generation of hybrid is healthy and fertile, but second generation have reduced survival or fertility
97
how does alternative splicing contribute to protein diversity?
- the exons of a gene can be assembled in different combinations to produce different isoforms with the same gene
- this ensures protein diversity
