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Ch. 9 Part I Video Lecture - AbeAPBio's library.flv

Added Nov 16, 2012 •

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the first of notes on chapter 9 about the cell cycle hopefully you'll find this a little easier to understand than photosynthesis and cellular respiration the cell cycle is an orderly set of phases through which a cell move during his lifetime there are two major divisions interface which you can see Discraft takes up the majority of a cell's life and mitosis is the process by which a cell replicates into two new cells we will go through each phase of the cycle in more detail right now let's look at an animation of the life cycle of a cell  most Marriott Excel follow a process of growth and division called the cell cycle these events include a growth stage mitosis or nuclear Mission and cytokinesis or division of the cytoplasm  trout interphase the cell is engaged in growth and metaball activities heater phase can be further broken down into three discrete faces called G1 s and G2 during the G1 nor first growth phase normal cell functions occur as well as cell growth in the S phase DNA replicates producing two copies of each chromosome  during the G2 phase the cell continues to prepare for mitosis and cell division mitosis or the M phase has four stages prophase metaphase and plays and telophase during prophase the chromosomes become visible and condense becoming shorter and thicker each identical copy of a single chromosome is called a sister chromatid the nuclear envelope breaks down and spindle fibers for arm is microtubules grow out of the centrioles that move to opposite poles of the cell  during metaphase the double-stranded chromosomes line along the Equator of the cell the spindle is now fully formed and the microtubules attach to each sister chromatid  anaphase begins when the sister chromatids of each chromosome begin to separate the centromere that holds sister chromatids together divides and the chromosomes move play from each other along its spindle fiber  in telophase the two groups of chromosomes reach the office cancel the cell as a new nuclear envelope starts to form around each group the chromosomes uncoil and the spindle disappears the division of the cytoplasm and organelles is called cytokinesis or the sea phase the result of mitosis and cytokinesis is the formation of two genetically identical cells  to summarize the entire cycle G1 s and G2 two phases occur during interphase while the cell is growing and preparing to divide mitosis or the division of the nucleus consists of phases prophase metaphase anaphase and telophase and in these faces duplicate copies of the chromosomes are split equally finally the cell cytoplasm divides during cytokinesis and result in the formation of two genetically identical daughter cells Savannah animation ticket through the entire cell cycle and the next set of notes the video lecture 92 is going to specifically reference my we're going to get into that and more. This time we're just going to worry about an overview of the cell cycle with interphase and how it's controlled so take a closer look and interface  notice again that this takes up probably 85 to 90% of a cell's life and if they this further broken down the three stages you saw in the animation during G1 the cell doubles its organelles and accumulates materials needed for synthesizing a second copy of a DNA in the nucleus think of G1 as short for first growth phase that phase is when DNA is copied so at the end there are two full and complete is of all the DNA found inside the nucleus we will learn exactly how DNA is replicated in Chapter 13 so as can stand for synthesis Duty was more time for growth and preparation for cell division with a cell synthesizes the proteins necessary for successful division G2 is the second growth and some background information here scientists used to think nothing much is going on during G1 and G2 so originally they were named he wanted me to 4 but now we know that a lot is going on and so they changed Gap to mean gross and so isn't it nice that growth also starts with a g you didn't have to rename me entire cycle  we're going to take much closer look at cellular division in our next of note cuz I've already said turn now let's briefly look at the stages of mitosis there's nuclear division which take the through prophase prometaphase metaphase anaphase and telophase I know the animation watched Dimension prometaphase and this just recently started to emerge as a phase of its own it used to just be part of prophase but more and more textbooks are highlighting it as a home safe so we will to just to make sure you're up-to-date then their side of Kinesis where the cytoplasm splits and two new genetically identical cells are formed by toes selfies with only takes between 30 to 90 minutes of a cell's life so how is the cell cycle regulated so it happens correctly are several factors first book at checkpoint to sell have to pass in order to continue in its cycle there are three checkpoints during this life one towards the end of the G One Faith one towards the end of the G2 phase and 1 towards the middle of mitosis at each checkpoint protein levels are checked inside the South good proteins are known as cyclin and the activate enzymes that are active during the cell cycle known as cyclin-dependent kinases Lakeland fluctuate up and down and if they aren't present at the appropriate level at each checkpoint a cell will not continue on in the cycle it will arrest stop for stop  there's another protein p53 that is essential in proofreading and checking the DNA of a cell to ensure accurate replica the entire genome to each new cell is able to function correctly if p53 finds any problems with the DNA it will help us out to allow her repair of the damaged DNA if it can't be repaired p53 will initiate apoptosis which is programmed cell death yep a cell will commit suicide if it is not prevent more defective cell from being formed caspases are the enzymes that actually caused apoptosis to occur or carry-out apoptosis so this dirty the stages of a cell undergoing apoptosis you see it rounds up the nucleus collapses chromatin can can you please fragments the plasma membrane blisters and then cell fragments contain DNA fragments at the end immune cells would phagocytize fragments to recycle them in the body animation that gives us a brief overview of the checkpoints of the cell so it will reinforce what I the process of cell growth and division in eukaryotes is called the cell cycle this cycle divided into phases based on what is happening in the Cell at a given time a cell grows during the G1 phase during this phase there is a local checkpoint that controls whether the cell will divide delay division or enter a resting stage when conditions in the cell are right the G1 point will be past and the cell will enter the synthesis S phase during the S phase DNA replication occurs so the future cells will eat have a complete set of the genetic instructions in the DNA  after DNA replication is complete cells enter the G2 phase where they can you to grow and prepare for cell division at a checkpoint in this phase the success of DNA replication is assessed if all is well the cell enters the closest M phase during the M phase a complex series of events move the DNA so that a complete set of genetic instructions will be sent to daughter cell the process of mitosis is assessed at a checkpoint during the M phase once the checkpoint is passed the cell will complete my this as well as begin the cytokinesis see phase part or all of the sea phase actually overlapped with the later parts of mitosis so it is not distinctly separate phase during the cytoplasm of the cell is divided and two daughter cells are created from the original cell when this nice tattoos finished the daughter cells enter the G1 phase and the cycle is complete  super does wrong with the checkpoints the p53 protein or even apoptosis well a cell can enter abnormal growth cell growth and division that the out of control when do you turn mutated and the proteins no longer function correctly cells will grow and divide and tumors will form hopefully you are familiar with the terms benign and malignant which one is non-cancerous  black cracked malignant means the tumor is cancerous so if you have a tumor a doctor will biopsy take a small portion of that tumor and test for whether it's benign or malignant there are four characteristics of cancer cells you should know number they lack differentiation and had abnormal nuclei differentiation is a specific shape and function liver cells are different than red blood cells which are different from skin cells which are different from eisele's etc etc. Differentiation  number to they can form tumors because they left contact condition contact inhibition refers to the fact that normal healthy cells don't grow too big for one reason that they don't crowd earring self when things should tighten the space external factors will trigger the cell to divide because of that contact inhibition cancer cells don't respond to contact and I'll just keep growing and pushing Other Self out of the way  number 3 cancer cells can metastasize which means they can pregnant and travel through the bloodstream to form Chambers and other parts of the body and finally number for cancer cells can undergo angiogenesis which is where they form new blood vessels in addition to the body call blood vessels to feed the new cancerous about probably the number one indicator that a tumor is cancerous and not benign so it's malignant and not the nine is if it metastasizes if it's able to move through the body and form tumors elsewhere that's how when apoptosis doesn't work you can't develop the pathway that involve apoptosis or programmed cell death implicated in the development of many cancers cells and do the same pop ptosis in response to irreparable damage a key mediator of apoptosis due to DNA damage is the p53 tumor suppressor Gene however over half of human cancers exhibit mutations to the piece of the these mutations disrupt the sells natural suicide response to excessive cell growth and tumorigenesis they may also cause cancer spell to develop resistance to radiotherapy and chemotherapy  so you see here in this. This is that angiogenesis is formed on blood vessels to feed these cancerous cells so that they continue to grow and divide without any problems  so let's look a little more closely house can become cancer mutations are changes in DNA that are segments of DNA that code for the cell cycle regulator protein some of these segments of DNA are called proto-oncogenes that promote the cell cycle keep it running smoothly when they mutate they become Uncle Gene's the prefix opening cancer you learn on your Latin quizzes and these men cause cells to become cancerous the mutations to proto-oncogenes  understatement sad are called tumor suppressor genes which inhibit the cell cycle if something goes wrong so they're another control if these mutate they don't work and they don't stop the cycle even when a cell is deceased  finally there are portions of DNA called Tila mirrors that shorten with each cellular division when do a man's run out a cell will undergo apoptosis naturally however when it's down mutates into a cancer cell it begins to make deliveries and ends next to mirror so it never undergoes apoptosis so what can cause these mutations to the DNA well you can see here that heredity sometimes you inherit faulty genes radiation sources we've all heard of UV radiation causing skin cancer x-rays if you get trade all the time those type of things nuclear radiation pesticides and herbicides can be problematic no chemicals can cause mutations can even viruses can cause mutations there's been a big push about the HPV the human papilloma virus causing uterus cancer in female not caused by a virus HPV the virus stop the cell cycle G1 there is a chemical checkpoint that a cell must pass to begin the process that leads to cell division the protein products of tumor suppressor genes act at that checkpoint to control cell division cells with mutated forms of the tumor suppressor genes may not be go to stop the cell cycle at the G1 checkpoint thus allowing them to grow and divide rapidly and form a tumor one such tumor suppressor Gene the retinoblastoma RB Gene it is often found to be mutated in a form of cancer in the eye called retinoblastoma as well as in many other cancers will bind to a transcription Factor called what can activate gene expression the G1 checkpoint is past when special cell cycle proteins cyclin and cdk work together to free UF from RB the release transcription Factor then activates genes that start the cell on the path to cell division mutated forms of may not bind to eat you up allowing e2f to act without control to promote cell division another tumor suppressor protein that works at the you one check point is p53 this protein check for damage DNA acting as a quality control for the cell if damage is to then p53 both activates a DNA repair system and helps the cell cycle at the G1 checkpoint until the damage is repaired old is accomplished by turning on the gene for another protein p21 but keep cyclin and cdk from interacting as long as cycling Speedy K cannot form a complex the cell cannot pass through the G1 checkpoint the p53 gene is found to be mutated in a wide variety do cancers in these cases p53 fails to turn on p21 and dust is not halt the cell cycle like it should when DNA damaged in the animation that you don't have to know I wouldn't try to remember the RB protein but you should know people too it's going to come up again and again and again and you're going to learn more about how p53 works when we talk about DNA the other things you should know is cyclin and the cdk cyclin-dependent kinases are proteins and enzymes which are proteins that work to regulate the cell cycle and I would be familiar with those two terms as well so we learned about the cell cycle and our next video lecture I said we're going to learn about more about what happens during mitosis you were introduced to it a little bit in the but we will get down to the nitty-gritty in the next one before you leave I do want to do one more animation showing of the cell cycle on again repetition repetition Titian I'm hoping the more you see it easier to remember  so this is actually a website you can go to if you want to it's called Zelda live www.cellsalive.com I will post a link to it on the Kia page and on the left you can see interactive models of the cell that mitosis and Elsa's prophecies which we'll talk about and then the cell cycle so you can just play it he got interface you got DNA test the two and then mitosis work device  you can also choose to go through the checkpoint swear checkpoint and tell you what it checks for and you can click continue second checkpoint then you can click continue the third checkpoint right in the middle of mitosis and then you could click continue.  So then you can go to this website animation for yourself if you would like to review it  congratulations you've reached the end of the first video lecture on chapter 9 see you

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Ch. 9 Part I Video Lecture - AbeAPBio's library.flv

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