Topic 13: Evolution Flashcards
An organisms complete genetic makeup is contained within its?
Genome
Genomes can vary in what?
size, number of genes, and gene density between organisms
eukaryotes- genomes tend to be larger in most cases
Gene densities tend to be higher in what?
of genes per length of DNA
-higher in prokaryotes
-shorter DNA but still many genes results in higher densities
Multicellular eukaryotes have lots of non-going DNA and many multigenerational families contained within their genomes, what are they?
-introns (DNA between protein coding genes)
*20%
-gene-related regulatory sequences
*5%
-unique single copy DNA
-pseudogenes (former genes that no longer function)
-repetitive DNA (present in multi copies in the genome)
-simple DNA repeats
What are multigene families?
collections of 2 or more identical or similar genes
ex. global genes that make up hemoglobin
What are transposable elements?
are stretches of DNA that can move from one location to another within the genome
-moves via recombinant events
- Transposons-move by an intermediate enzyme called transposase (‘cut and paste’)
- Retrotransposons- move via an RNA intermediate (‘copy and paste’)
How to Transposable elements contribute to genome evolution?
- promote recombination
- disrupt celular genes or control elements
- carry entire genes or axons to new locations
What happens if a transposon jumps into the middle of a protein-coding gene?
it could prevent the normal transcription of the gene
What happens if a transposon jumps into the middle of a regulatory gene?
it increases or decreases the production of one or more proteins
What happens to genome evolution if duplication of entire chromosomes sets?
errors in meiosis (such as failure to separate homologous chromosomes can result in polyploidy
-usually lethal, some cases can facilitate gene evolution
-duplicated genes have mutation that occur that allow them to function differently
-pass these duplicated genes to offspring
-many plants evolve this way
What is divergent evolution? ***
lecture 32 slide 9
Duplicated of gene-sized regions of DNA can contribute to genome evolution how?
errors in meiosis can cause duplication of chromosomal regions
-unequal crossing over during prophase 1 can results in chromosomal deletions in one chromosome and chromosomal duplicated in the other
How can human global genes evolve from duplication events?
-a single global gene underwent duplication and divergence
-mutations in the diverged global genes results in two different functioning genes on two different chromosomes
How can related genes have different functions after duplication and divergence?
-lecture 32 slide 12
How do exons lead to genome evolution?
EXONS ARE DNA sequences THAT CODE FOR PROTEINS
-can be duplicated or deleted in homologous chromosomes due to unequal crossing over in meiosis
-duplicated exons could code for more of the protein, resulting in protein stability within it domains, increase ability to bind to ligands
IF different axons are moved within a gene or between two different genes due to errors in recombination during meiosis, this exon shuffling could lead to new proteins with novel functions
The more similar in sequences the genes and genomes of two species are they are closer or further in evolutionary history?
the more closely related they are in their evolutionary history
What does it mean to be highly conserved?
genes that have remained similar over time are highly conserved
What does comparing genes show us?
allows us to see if certain genes are evolving faster in certain organisms
Genes that code for transcription factors evolve faster or slower?
evolve faster than others
Comparing genomes within the same species allows us to see what?
genetic differences that lead to diverse phenotypes
-most genetic variation appears in the form of single nucleotide polymorphisms (SNPs), which are single base pair sites found in at least 1% of the population
-also occur from copy-number variants, where individuals have one or multiple copies of a gene or gene region (caused by duplication) father than one copy per homologue
What is evolutionary development?
is the study of developmental processes of different multicellular organisms
-goal: to understand how processes evolved and how these changes modify existing organismal features or lead to new ones
What is a homeobox?
180-nucleotide sequence that goes for a 60-amino acid homeodomain
What are homeotic genes?
master regulatory genes that control placement and spatial organization of body parts in organism by controlling the development fate of groups of cells
What was Charles Darwin scientific explanation for 3 observations?
- the striking way organisms are suited for life in their environment
-natural selection, adaptations - the many shared characteristics
-(unity) of life - the rich diversity of life
-descent with modification
-branched, not linear
What is Charles Darwins definition of EVOLUTION?
evolution to be descent with modification
-species are descendants of an ancestral species that were different from the species we see today
evolution is both a pattern and a process
pattern: scientific evidence
process: natural observed changes
What was Aristotles early ideology?
Aristotle (384-322 BCE) saw species as unchanging/ fixed
-scale naturae (scale of nature)
-basis of Old Testament, life is permanent and perfect
What was Carolus Linnaeus early ideology?
Carolus Linnaeus (1707-1778) classified life according to their similarities
-Linnaean classification of taxonomy
-nested classification compared to Scale Naturae
-described based on pattern of their creation (what they looked like)
What were Darwins theories influenced by?
1.Fossils
-remains of traces of organisms from the past
-contained within rock layers called strata
- Slow and Subtle processes were changing organisms over time
What was Georges Cuvier’s idea?
(1769-1832) notes older strata had different species than newer strata
-speculated that each stratum represented a single catastrophic event leading to the extinction of that species
What was James Hutton’s idea?
(1726-1797) proposed that Earth’s geological features were a result of gradual processes (erosion, valleys being formed by rivers)
What was Charles Lyell’s idea?
(!797-1875) proposed that the same geological processes in the past were occurring in the present, at the same rate
(based off James Hutton’s idea)
What did Jean-Baptiste de Lamarck propose?
(1744-1829) proposed the first hypothesized mechanism for evolution
-suggested: evolutionary change explains that patterns seen in the fossils and how certain organisms are found in certain environments
-suggested: (1809 year Darwin was born)
there were multiple lines of descent.
-suggested: it was explained by use and disuse
-body parts that were needed became stronger and larger, body parts that were no longer needed deteriorated
ex. giraffes long necks
-suggested: inheritance of acquired characteristics
could be passed too offspring
suggested: organisms had a nature need to become more complex
What was Darwins observation of adaptations?
Galapagos Islands
-darwin’s finches had different beak size and shapes based on environment and food sources
What is natural selection?
where individuals that have certain inherited traits tend to survive better and reproduce due to those traits
NOTES TO REMEMBER:
1. individuals do not evolve, populations do
2. traits must be heritable and vary within a population for selection to occur
3. favourable traits depend on the context of the environment; evolution is not goal directed
What is a common ancestor?
similar organisms that share a common ancestor from which they formed
Diverse environment means diverse selective pressures, what do they lead to?
- leads to diverse adaptation to the environment
- lead to new divergent species
What is Adaptive Radiation?
a process in which organisms diversify rapidly from an ancestral species into a multitude of new forms, particularly when a change in the environment makes new resources available, creates new challenges or opens new environmental niches
What do phylogenetic trees show?
- dedicated are the evolutionary relationships of vertebrates
- all organisms here have been evolving for the same amount of time
What is Artificial Selection?
Darwin notes that humans have modified other species by selective breeding with desire traits
-trait must be variable in the species and heritable
What factor provides selective pressure?
the environment
-takes a LONG time
-different population adapt to their environments and eventually become separate species
What is Relative Fitness?
Contribution an individual makes to the gene pool of the next generation relative to other individuals in that population
-reproductive success of an individual
-better term for “survival of the fittest”
examples:
-no genetic disorder, no disease, surviving environmental condition, not getting eaten, ability to attract a mate
Natural Selection cannot make a “perfect” organism, why?
- selection can only act on existing variations
-favours only fittest variants from phenotypes available
-may not be the best trait for an environment - Evolution is limited by historical constraints
-each species has a leafy of “descent with modification” from ancestral forms
-evolution doesn’t start ‘fresh’, but modifies previous ones and adapts to existing conditions - Adaptations are often compromises
