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Lecture 24

Biology 2581B Lecture 24: Lec 24 - MFTs

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Western University
Biology 2581B
David R Smith

Lecture 24 – MFTs Marine slugs - Aka: Solar powered opisthobranchs o They are green because they perform photosynthesis - It is not just one species that does this, there are a number of species o ANIMALs that photosynthesize - This marine snail Elysia chlorotica “kidnaps” chloroplast by eating algae o Eats chloroplasts and keeps them o The plant becomes photosynthetically active by using the chloroplast - “Scientists have shown that once a young slug has slurped its first chloroplast meal from one of its few favored species of Vaucheria algae, the slug does not have to eat again for the rest of its life. All it has to do is sunbathe.” o Derives it energy by eating chloroplasts - They found in the marine slugs: o 101 chloroplast-encoded gene sequences o 52 nuclear-encoded genes o From the chloroplast donor, Vaucheria litorea. - The symbiotic chloroplasts are translationally active o Genes are transcribed and translated - Marine slugs control the chloroplasts on their own similar to what happens in plants - Functional algal genes have been transferred into the slug genome - The symbiotic chloroplasts residing inside the host molluscan cell are maintained by an interaction of both organellar and host biochemistry directed by the presence of transferred genes - “Evolution on the go” – things are still changing Trypanosomes - Are parasites o Live in insects o Live in mammals o Carrier of sleeping sickness o Live in blood stream of humans - There is a host system: o When an insect carries a trypanosome and it is having a blood meal, it will inject it into the bloodstream and it will develop in there o Insect with pick up the trypanosome again and it will migrate into the midgut o Parasite is transferred into the next mammalian system - Have interesting genomes in their mitochondria o In particular areas in the mitochondrial genome, they are very densely packed with their genomes o Very dense - Many genomes stacked up that form a genome that is shaped like a hockey puck - Circular genomes o When spread out, there are 100s-1000s of circular genomes in this arrangement o Mini the center o Maxi circles extend outside when spread o A spread is not how it actually looks like - Mini circles are stacked up o Diameter of a circle is shown in the picture o Many circles are next to each other and form the “hockey puck” - When they get spread, they are networked o Not single molecules o They are interlinked to each other o One is always interlinked with 3 others - Chain mail models o DNA is flexible - Valency: how many rings are interconnected and the valency can change – density - Mini circle is always interlinked with 3 others o VALENCY of three - 100s-1000s mini circles that need to be replicated o Duplicate all the rings o Double the number of rings that exist but the hockey puck does not change in size - There are 2x as many mini circles as before but the size doesnot change - Mini circles can change their valency o Instead of being linked to 3 circles, they are linked to 6 circles - High valency/interlinkage then the density of the circles increase - Increase the number of circles during replication: o By changing valency at the same time, can package mini circles in the same place as before replicate - After replication is complete, separate out into daughter organelles and valency will decrease again to 3 - Repeat process - Very complicated process – difficult to replicate many circles and not lose track of them Tetrahymena - Eukaryotic protist - Can conjugate o 2 cells can connect to change genetic information in the form of DNA - Has two nuclei (2 different types of nuclei) o Macronuclei and micronuclei o Names come from the size difference - MICRONUCLEUS: a diploid germline nucleus that remains transcriptionally silent throughout asexual reproduction o Represents germline nucleus that is passed on o BUT IT IS SILENT –it is the information storage unit o Information of a genome is stored in the micronucleus ▪ BUT the information is not directly used in the form of transcription - MACRONUCELUS: a somatic nucleus that is transcriptionally active o Active: transcribe RNA then translate it into protein o Information in this nucleus makes up protein make up of the cells - Rearrangements occur in the genomic o Macronucleus mates with a new tetrahymena o When the mating occurs, can have rearrangements in the genomic organization ▪ This leads to the formation of sexes - Tetrahymena has SEVEN different sexes o All look the same... but there is a difference - Can mate with any mating type but its own o Can mate ONLY with DIFFERENT mating type o They can recognize different sexes which involves genome rearrangements - Outcome of rearrangements is random o Process is referred to as genomic roulette - Programmed genome rearrangement and as the outcome is random and not predictable it has been called “genomic roulette” - Germline genome has certain types of genes and they encode proteins that are required for sexual determination o Nothing changes here o Germline genome stays the same - In the macro nuclei, things get rearranged based on recombination events - Recombination occurs and outcome can be the tip of the arrow that is attached to orange arrow recombines with the the blue unit o Everything else gets deleted in the processes - In macronuclei, have only ONE of the units that is representative of a particular sex - Can have a different recombination event in a different individual o E.g. yellow unit is the baseline ▪ Need 2 recombination events to catch some of the blue and orange area - Recombination events can occur with all of the units o Generate 7 different outcomes BUT they keep the original copy in the germline o Modify when they make the macronucleus - Genes code for membrane proteins - There are different domains encoded in the genes o Part of the coding domains make transmembrane domains that are always the same - Transmembrane domains are encoded by the TIPS o They all need blue and orange tips o Transmembrane domain anchors the protein into the membrane - The rest of the information makes a domain that is on the OUTSIDE of the organism o Membrane coding unit is anchoring that domain on the outside o Different organisms have different membrane coding units - Defines what the sex of an organism: o Membrane coding unit on the outside of the organism can be recognized by a different individual with a different membrane coding unit - Only mate if encounter someone with a different mating type - Recombination leads to the production and generation of transcription units that result in different proteins that have a particular purpose in the life time of an organism - Blue and orange tips must be apart of every unit because they make the transmembrane domains - The rest of the protein faces the outside of the organism and defines the sex GFP – green fluorescent protein - Discovered in jellyfish - It all started in the 1960 when someone performed research with jellyfish Aequorea victoria: Osamu Shimomura to understand why they glow o Discovered that glowing of jellyfish is a result of a protein - Bioluminescent protein o Protein used for many purposes o Use the protein to look at cellular processes - Beta barrel protein with a chromophore: three amino acids in the center of the protein o Glowing is because of 3 amino acids in the center o Part of the protein is inside the barrel o 3 amino acids are the cause for the luminescence that the protein exhibits o Chromophore is in the center of the beta sheet structure - Can exchange amino acids and get many different types of c
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