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Class Overview There will be an extra credit opportunity in this class You have to register for PSOs to be able to come I am registered for Tuesday 5 30 6 20 in Lily G 126 but I can also attend Monday 1 30 2 20 in Stewart Room 320 Each PSO session reviews the previous session because multiple choice quizzes are over the previous week s lab and lectures Lectures are usually slightly ahead of Labs Course Overview Cell cycle division mitosis and meiosis Genetics Mendelian and non Mendelian inheritance Gene expression how info stored in DNA is used to direct production of proteins Cellular communication Development Physiology circulation and gas exchange neuronal and muscular function endocrine signaling immunity waste and water balance etc Ploidy and Genetic Info In Biology we use n both as a measurement of the amount of information and the number of different chromosomes in a set A human sperm has n information A human ovum surrounded by sperm has n information Together they make a human zygote with 2n Ploidy number of sets of chromosomes in a cell 1n 1 chromosome in a set haploid 2n 2 chromosomes in a set diploid 3n 3 chromosomes in a set triploid 4n 4 chromosomes in a set tetraploid seen in frogs for example ex seen in flowering plants The number of chromosomes in a set is not the same as the unique types of chromosomes For example humans have 23 types of chromosomes and they are diploids two each This means that for humans they have 23 2 46 chromosomes Peas on the other hand have 7 types of chromosomes They are also diploids 2n so they have 7 2 14 chromosomes For eukaryotes we will be focusing on sexually reproducing diploid organisms Occasionally mistakes will happen This is known as Aneuploidy which means not having the TRUE number of chromosomes An extra chromosome Down Syndrome Missing a chromosome Where females have only one X chromosome in Turner syndrome for example Cell Division is needed to heal wounds grow the body evolve the body and reproduce Reproduction is a key element of life that requires 3 things 1 Replication of genetic material 2 Accurate segregation of genetic material 3 Division of cytoplasm Interphase Cell Division Cytokinesis This process needs to be controlled and responsive to environmental conditions What happens if cell division is uncontrolled This leads to tumors and cancerous growths Prokaryotes have no organelles or internal compartmentalization but Eukaryotes do have those things Eukaryotes divide by Mitosis 2 daughter cells or Meiosis 4 daughter cells It should be mentioned that prokaryotes have a very simple form of asexual cell divsion called binary fission but it is NOT the same thing as Mitosis or Meoisis It still requires replication and segregation of genetic material but the genetic material is highly compacted and twisted because there is so much less room which simplifies the replication and segregation process For example E Coli s chromosome is about 1400 um but the E Coli length is about 2 um So the genetic information that is going to be put in that chromosome is super twisted and condensed Cell Cycle Binary fission is an asexual reproduction where replication is immediately followed by segregation This is very different from eukaryotes where there is time in between replication and segregation We once thought this was passive but now we know it is active It requires specific proteins a b Most bacteria and archaea produce FtsZ proteins see textbook notes for Chapter 10 c Septum new cell wall forms at the site of the ring of FtsZ protein to split the cell wall in a process called septation d FtsZ resembles tubulin which is normally used to create microtubules in eukaryotes suggesting an evolutionary link The chromosome is basically a twisted circle of DNA Replication starts at the origin and stops at the terminus The cell elongates at this point Cyanobacteria are photosynthetic bacteria that circulate oxygen in the atmosphere and we use them as an example of the regulation of FtsZ proteins They actively grow about 19 hours a day Because of all the runoff from chemicals seen in fertilizers and stuff they are exposed to lots of nutrients and they grow like fucking crazy When they grow like this they produce toxins that are damaging to the livers neurons and kidneys This is why cell growth needs to be regulated If they are growing too much it leads to toxins Three genes Kai A Kai B and Kai C regulate the expression of FtsZ This means that when they are being expressed they let the cells divide again and again The DNA molecule of a bacteria prokaryote is usually circular The DNA molecule of a eukaryotic organism is usually linear with a point of constriction the centromere What is the Condition of DNA at Each Point in the Eukaryotic Cell Cycle The chromosomes start decompressed in Interphase It s basically big purple spaghetti The chromatids have not yet quite come together so it is pretty much invisible They start to compress and it looks like one chromosome with one chromatid Then it replicates and becomes one chromosome with two chromatids Then it splits and becomes two chromosomes with one chromatid Rinse and repeat Replication and chromosome separation occur at different times S phase and mitosis Chromatids need to stay together until separation Release of attachment is irreversible Components and Compaction of DNA Chromatids are one huge long molecule of DNA that can t fit into the cell So it has to be folded a ton But how does it compact DNA charge is complexed with basic histone proteins charge 2 H2A 2 H2B tetramer 2 H3 2 H4 tetramer Two tetramers one of each kind are connected by Linker DNA to make a histone octamer DNA spools around the histone octamer creating nucleosome which in turn helps create chromatin Chromatin is 40 DNA and 60 protein and this is why The nucleosome is the first level of compaction It is further wrapped into a higher order coil called the solenoid this is a condition of interphase during chromatin Solenoid is further coiled and radially wrapped around the protein scaffold to make the metaphase chromosomes If we deconstruct chromosomes it looks like this Chromosomes rosettes of chromatin loops chromatin loops solenoids nucleosomes DNA double helix that we know and love Enzymes There are a few enzymes we need to look at to help with the cell cycle I covered these in my Chapter 10 Bio Notes but they are Cylins named so because they are regulatory proteins in a cyclical fashion that increase going into

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Purdue BIOL 10200 - Ploidy and Cell Cycle Notes

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