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75 Cards in this Set

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Transcription

The synthesis of RNA from a DNA template

RNA Polymerase

Responsible for synthesis of RNA

Holoenzyme

-RNA is a core enzyme that binds to sigma


-Sigma recognizes and binds to the promoter

RNA Splicing

-snRNPs edit mRNA in the nucleus and excise introns(noncoding sections of RNA transcript)


-Splice the exons(code for proteins) together to form edited mRNA

Adding Caps and Tails to RNA Transcripts

-Addition of 5' cap


-Addition of a poly(A) tail


-Importance of this process:


---Prevents premature degradation by enzymes


---Increased amounts of translated protein


---Checking mechanism for nuclear export

Transcription and Translation

occur simultaneously in bacteria (both processes occur in the cytosol in bacteria)



mRNA in Eukaryotes

Must be exported from the nucleus to the cytosol for translation

tRna is an adapter molecule

-Amino acids are brought to the ribosome by transfer RNA molecules


--Anticodon region that recognizes an mRNA codon via base pairing


--tRNA is charged with an amino acid at the 3' end (aminoacyl tRNA synthestase)

E Site

Holds a tRNA that will exit

P Site

Holds a tRNA with growing polypeptide attached

A Site

Holds an aminoacyl tRNA

Initiation of Translation

-Initiation proteins manage assembly of ribosomes and mRNAs


-mRNA binds to small subunit


--Ribosome binding sequence on mRNA (Shine-Dalgarno sequence)

Elongation of Polypeptide During Translation

1) Incoming aminoacyl tRNA


2) Peptide-bond formation


3) Translocation


Repeats itself another three times

Terminating Translation

Meditated by proteins called release factors (looks like tRNAs, binds tightly to the A site)


1) Release factor binds to stop codon


2) Polypeptide and uncharged tRNAs are released


3) Ribosome subunits seperate

Evolution is a property of life

The theory of evolution by natural selection ranks alongside other scientific theories


-Copernicus theory of the sun as the center of our solar system


-Newtons law of motion and theory of gravitation


-Germ theory of disease


-Chromosomal theory of inheritance


-Theory of plate tectonics


-Einstein's theory of relativity

Evolution by Natural Selection

Ideas of Wallace and Darwin challenged explanations of the diversity of life


-leading explanation of diversity at the time was special creation


-Special creation asserts that:


1) All species are unrelated


2) Life on Earth was ~6000 years ago


3) Species are incapable of change

Wallace and Darwin were the first to use scientific principles in their explanation of diversity of life

Two components:


1) Pattern component (a statement that summarizes a series of observations about the natural world)


2) Process component (a mechanism that produces that pattern or set of observations)

Evolutionary Thought

Wallace and Darwin were not the first evolutionary thinkers:


1) Aristotle


2) Plato


3) Jean-Baptiste Lemark





Wallace and Darwin changed evolutionary thought

1) Species are dynamic and can change over time


2) Replaced typological thinking with population thinking


3) Evolution by natural selection was testable through experimentation (Species change through time and are related through a common ancestry)

Extant

Currently living

Transitional Features

Tetrapod Limb


-Tulerpeton (362 mya)


-Tiktaalik (375 mya)


-Acanthostega (365 mya)


-Eusthenopteron (385 mya)

Vestigal Traits

Reduced Versions of traits in other species

Biogeography

Closely related species often live in the same geographic area

Homology

Similarity that exists between species because they inherited the trait from a common ancestor

Genetic Homology

Pax6 is homologous gene in the mouse (similar gene in other species)


-Modified in each lineage


ex:Aniridia (Human) without iris


Fruitflies (eyeless)

Developmental Homology

Structures that appear early in development are similar (embryology)



Structural Homology

Structures that are similar in adult morphology

Evidence for Evolution

Prediction 1: Species are not static, but change through time


Prediction 2: Species are related, not independent

Evolution produces a tree of life

Bacteria--Archae--Flowering Plants--Mosses--Tapeworms--Vertebrates--Fungi

Four Mechanisms that alter allele frequencies in a population

1) Natural Selection: Increases frequency of alleles that contribute to reproductive success in a particular environment


2) Genetic Drift: Causes allele frequencies to change randomly


3)Gene Flow: Addition/deletion of alleles in a population of breeding individuals by migration/immigration


4) Mutation: Modifies allele frequencies by continually introducing new alleles

Hardy-Weinberg Principle (Cannot have any of the four mechanisms)

Acts as a null hypothesis when we want to know whether evolution is occuring at a particular gene


-Genotype frequency: p2+2pq+q2


-Allele frequency: p+q=1

Directional Selction

Favors one extreme phenotype cause


the average value of a trait to change


-Genetic variation is reduced

Stabilizing Selection

Favors phenotype near the middle of the range


and reduces the amount of variation in a trait


-genetic variation is reduced

Disruptive Selection



Increase the amount of variation in a trait


-Genetic variation is increased

Balancing Selection

No single phenotype is favored in all populations


-Genetic variation is maintained

Genetic Drift

Changes in allele frequency as a result of random events


-Random with respect to fitness


-Most pronounced in small populations


-Over time can lead to the random loss or fixation of allele



Founder Effect

New population is likely to have different allele frequencies than the source population by chance

Genetic bottleneck

Bottleneck population is likely to have different allele frequencies than original population by change

Gene Flow

Movement of alleles from one population to another

Mutation

-Mutation increases genetic diversity in populations (Random)


-Mutation does not occur enough to make it an important factor in changing allele frequencies

Nonrandom mating

Hardy-Weinberg principle is based on random, chance matings, however in nature matings may not be random with respect to the gene in question



Interbreeding

Mating between relatives (increase homozygosity)

Sexual Selection

Occurs when individuals within a population differ in their ability to attract mates


-choosy females


-male-male competition

Sexual Dimorphisms

Sexually dimorphic traits are those that vary between males and females


-results from sexual selection

Species

An evolutionary independent population or group of populations


Three Criteria:


Biological Species


Morphospecies


Phylogenetic

Biological Species Concept

Populations are evolutionarily independent if they do not interbreed


-Populations are reproductively isolated


-Pre-zygotic barriers


(prevents individuals from mating/breeding)


--Temporal, habitat, behavioral, gametica, mechanical


-Post-zygotic barriers


(Offspring from mating between individuals of different species do not survive (or reproduce)


--Hybrid viability, Hybrid sterility



Temporal

populations are isolated because they breed at different times

Habitat

populations are isolated because they breed in different habitats

Behavioral

Populations do not interbreed because their courtship displays differ

Gametic Barrier

Matings fail because eggs and sperm are incompatible

Mechanical

Matings fail because male and female reproductive structures are incompatible

Hybrid viability

Hybrid offspring do not develop normally and die as embryos

Hybrid Sterility

Hybrid offspring mature but are sterile as adults

Morphospecies Concept

Based on features associated with size or shape of other physical differences

Phylogenetic Species Concept

Identifies evolutionarily independent lineages based on reconstructing an evolutionary history of a population

Allopatric Speciation

Genetic isolation that happens routinely when populations become physically separated

Sympatric Speciation

Speciation events that take place in the same geographical area


-No physical barrier that prevents interbreeeding

What happens when two populations that had been isolated come into contact and there are no prezygotic reproductive barriers in place?

1) Fusion


2) reinforcement


3)Hybrid zones


4) Extinction of one population


5) Development of a new species

Fusion of the population

Two populations freely interbreed (when same species come in contact)

Reinforcement of divergence

Hybrid offspring have low fitness, natural selection favors the evolution of traits the prevent interbreeding between the populations

Hybrid zone formation

Hybridization occurs in a well-defined geographic area. This area may move over time or be stable

Extinction of one population

One population or species is a better competitor for shared resources, then the poor competitor may be driven to extinction

Creation of new species

Combination of genes in hybrid offspring allows them to occupy distinct habitats or use novel resources, they may form a new species

Homology

Similarity in organisms due to common ancestry

Monophyletic group

Evolutionary unit that includes an ancestral population and all of its descendants but no others (also called a lineage, or clade)

Synapomorphy

A shared, derived trait

Homoplasy

Similarity in organisms due to reason other than common ancestry

Polyphyletic group

An unnatural group that does not include the most recent common ancestor

Paraphyletic group

A group that includes an ancestral population and some of its descent but not all

Habitat Bias (Limitations of fossil record)

Areas where sediment is actively being deposited, organisms are more likely to fossilize

Taxonomic and Tissue Bias (limitations of fossil record)

Organisms with hard shells, bones, or casing are more likely to fossilize

Temporal Bias (Limitations)

Recent fossils are more common than ancient fossils

Abundance bias (limitations)

Widespread, abundant, or long-lived organisms are represented in the fossil record more often

Phanerozoic Eon is divided into three eras:

Paleozoic, Mesozoic, and Cenozoic

Each of these are a further divided

Periods and Epochs