BIOL 203 - Final Study Flashcards
What are micronemes?
Organelles found in Apicomplexans
Responsible for releasing proteins (adhesins) and other components that allow the parasite to invade host cells.
Initiate host-cell recognition and and anchoring.
What are four types of locomotion in protists?
Flagellar swimming, Amoeboid locomotion, Cilliates walking with cirri, Gliding
Where are raphe found and what does it do?
Raphe are slits found in the frustule of pennate diatoms.
It is a slit that allows them to connect to a substrate by secreting a sticky saccharide called mucilage.
Myosin and gliding in diatoms
Myosin is a motor protein that moves along microfilaments.
Adhesive mucilage attaches to transmembrane protein complexes which are subsequently attached to myosin.
Myosin moves towards the posterior of the cell pulling the diatom along the surface.
When myosin reaches the end of the actin road, the mucilage is cleaved and the myosin is recycled to the anterior of the cell to repeat the process.
Flagellar gliding in Chlamydomonas
Dyeins act on modified IFT trains while the glycoproteins attach to the substrate for traction.
The movement of the dyeins towards the base of the flagellum pulls the cell in the opposite direction.
Intraflagellar transport (IFT) trains
Complexes used to transport proteins up and down the flagellum.
Carried along the axoneme by Kinesin and Dyein.
Fused to glycoproteins (sticky) in plasma membrane.
Apicomplexan gliding
Myosin is attached to a protein complex that transverses the alveoli and is attached to the cells cytoskeleton.
Transmembrane proteins bind to short transient actin filaments via more proteins and host cell receptor.
When actin is pushed by the motor protein the apicomplexan moves.
Cell moves in same direction as myosin.
What constitutes gliding?
Happens on substrate
Utilizes cytoskeleton, motor and transmembrane proteins
Steps of apicomplexan parasitism
Micronemes release adhesins
Create parasitophorous vacuole
Rhoptries discharge lipids and proteins that modifies the membrane of the vacuole to avoid it being destroyed.
Dense granules release lipids and proteins that change the content of the P.V. to create optimal conditions for survival and replication.
Dense granules function
Discharge content in last step of apicomplexan parasitism to change the content of the lumen of the P.V. to create optimal conditions.
Rhoptries function
Discharge lipids and proteins to modify the membrane of the parasitophorous vacuole to keep it from being targeted and destroyed.
Very basically, what happens when a new parasite is introduced to the human immune system?
Something on the parasite’s surface (protein, sugar, etc..) is identified as a target. This molecule is an antigen.
The immune system synthesizes a novel protein that can bind to the antigen: an antibody.
Antibodies are mass produced, targeting the parasite and/or by guiding white blood cells to destroy it.
After the infection is cleared, some antibodies are stored for future purposes.
How do trypanosomes avoid the immune system?
Trypanosomes cover themselves in Variant Surface Glycoproteins (VSG).
When the immune system starts producing antibodies targeted at VSG it sheds the VSG and produces a brand new coat of proteins VSG2.
Pseudogenes
A gene not used over multiple generations accumulates deleterious mutations and becomes non-functional.
What are the three ways Trypanosoma brucei increases variability?
Switching which chromosome has its VSG gene expressed.
Moving a VSG gene from an inactive upstream pool into the expressed site via recombination (few hundred options).
Recombining pieces of genes and pseudogenes to create a new chimeric or mosaic of VSG genes.
Steps of microsporidian infection
Water is absorbed by vacuole increasing intracellular pressure.
Chitin wall breaks at weak point and the polar filament everts
Everted polar filament (Polar tube) pierces the host membrane.
Organelles are pushed through the polar tube where new cells form inside the host. (extra membrane material comes from the polaroplast)
Polar tube breaks with most organelles are now in a newly formed cell inside host.
Unusual genes in the nuclear genome of trypanosomes.
Arranged in long linear clusters.
Don’t have typical promoters.
Transcribed in long polycistronic mRNA’s
Spliced leader is
Three main features of ciliates?
Cilia
Nuclear dimorphism
Conjugation
Three main types of ciliates?
Paramecium
Tetrahymena
Oxytricha
Germline and Soma
Gametes and the cells they produce
Soma: Every other tissue
Differences between micro and macronucleus?
Micro:
-Transmitted to next generation after sex.
-Germline
-Usually not expressed
-Doesn’t do much other than being transmitted
-Fewer, longer chromosomes
-mitosis+meiosis
-Diploid
-Complete but non-functional genome
Macro:
-Lost by next generation during sex
-Somatic nucleus
-Always expressed
-Does basically everything
-More, shorter chromosomes
-divides in weird way
-Polyploid
-Incomplete but functional genome
How many less sets of sequences do Tetrahymena, Paramecium and Oxytricha have?
Tetrahymena: 34%
Paramecium: 25%
Oxytricha: 95%
How does the MAC split?
Through an unkown process
How does the MIC divide?
By mitosis every asexual cell division.
What is conjugation?
Sex
Happens once every many asexual cycles
Triggered by stress, environmental changes, etc..
Requires two cells of compatible mating types
Conjugation step-by-step
Cells of compatible mating types partially fuse
MIC undergoes meiosis but 3 of 4 haploid MICS degrade
MIC’s undergo mitosis
1 MIC from each partner transfers to the other partner
Karyogamy (two haploid nuclei fuse to form a diploid nucleus)
MIC’s undergo mitosis and the MAC starts to degrade
1 MIC starts developing into new MAC
Seperation
What is involved in the differentiation of a MIC into a MAC?
Deletion of MIC specific non-functional DNA sequences.
Fragmentation of chromosomes into chromosomes of a smaller size.
Amplification of the remaining chromsomes
What are the sequences present in the MIC but not the MAC?
Internal eliminated sequences
Tetrahymena and Paramecium MIC developing into new MAC steps
Entire DNA is transcribed in MIC
RNA is cut into tiny pieces (scnRNA’s)
scnRNAs are moved to the OLD MAC
scnRNAs base pair with matching DNA
scnRNAs that DO match are destroyed
remaining scnRNAs are moved to the differentiating MIC
Remaining scnRNAS base-pair with matching DNA
snRNAs mark the matching DNA to be destroyed
Oxytricha MIC developing into new MAC steps
each chromosome in the OLD MAC is transcribed
these long RNAS are moved to the differentiating MIC
The RNAs base-pair with matching DNA
The DNA sequences not matching the RNAs are targeted and destroyed
The long RNAs then guide the rearrangement of scrambled genes
Evolution
Changes occurring in biological populations over the course of generations
Natural selection
Differential success in reproduction among individuals in a population due to differences in their fitness
(Mechanism)
Genetic drift also a mechanism
Relative frequencies
How many features can be explained by one force (or a specific combination of forces)?
Strength
How rapidly can one force change the genetic makeup of a population?
How rapidly can a force fix or purge a new mutation in a population
Selection coefficient (s)
The advantage or disadvantage of a trait (-1 to 1)
When is natural selection strong?
When s is large or population size is large
Traits for which N |s|«_space;1 are:
effectively neutral and evolve by genetic drift
What is the main evolutionary force acting over most regions of eukaryotic genomeS?
Genetic drift
What is the only force that on its own can achieve, and is required for, adaptation?
Natural selection
What is a more complex system?
A system that has more components is considered more complex
Excess capacity
Redundancy of function in biological function
Might change the effect of a mutation from strongly deleterious to nearly neutral (pre-suppression)
Flow of genetic information: Bacteria and archaea
Gene – (Transcription) –> Polycistronic mRNA –(Translation)–> Protein
Flow of genetic information: most eukaryotes
Gene –(Transcription)–> monocistronic mRNA –
(cis-splicing to remove introns)–> monocistronic mature mRNA –(translation)–> Protein
Flow of genetic information: Trypanosomes
Gene – (Transcription) –> polycistronic mRNA –
(trans-splicing)–> monocistronic mRNA –
(cis-splicing to remove introns)–> monocistronic mature mRNA –(translation)–> Protein
Flow of genetic information: Ciliates
Incorrect MIC gene –(IES removal)–> Correct MAC gene –(Transcription)–> monocistronic mRNA –
(cis-splicing to remove introns)–> monocistronic mature mRNA –(translation)–> Protein
Flow of genetic information: most eukaryotic mitochondrial genes
Gene –(transcription)–> mRNA –(Translation)–> Protein
