The Cell Cycle Essay Example for Free

The Cell Cycle Essay I. Concept 12.1- Cell division results in genetically identical daughter cells A. Overview 1) The continuity of life is based on the reproduction of cells or cell division. 2) The cell division process is an integral part of the cell cycle, the life of a cell from the time it is first formed from a dividing parent cell until its own division into two cells. B. Cellular Organization of the Genetic Material 1) A cell’s endowment of DNA, its genetic information is called its genome. 2) Before the cell can divide to form genetically identical daughter cells, all of the DNA must be copied and then two copies separated so that each daughter cell ends up with a complete genome. 3) The replication and distribution of DNA is manageable because the DNA molecules are packaged into chromosomes. 4) The nuclei of a human somatic cell (all body cells except the reproductive cells) each contain 46 chromosomes made up of two sets of 23, one set inherited from each parent. 5) Reproductive cells or gametes-sperm and eggs-have half as many chromosomes as somatic cells, or only one set of 23 chromosomes. 6) Eukaryotic chromosomes are made of chromatin, a complex of DNA and associated protein molecules. C. Distribution of Chromosomes During Eukaryotic Cell Division 1) After DNA duplication, the chromosomes condense: Each chromatin fiber becomes densely coiled and folded, making the chromosomes much shorter and thick. 2) Each duplicated chromosome has two sister chromatids. The two chromatids, each containing an identical DNA molecule, are initially attached along their lengths by adhesive protein complexes called cohesins. This attachment is known as the sister chromatid cohesion. 3) The duplicated chromosome has a narrow waist at the centromere, a specialized region where the two chromatids are most closely attached. 4) Later in the cell division process, the two sister chromatids of each duplicated chromosome separate and move into two new nuclei, one forming at each end of the cell. 5) Mitosis, the division of the nucleus is usually founded immediately by cytokinesis, the division of the cytoplasm. 6) You produce gametes by a variation of cell division called meiosis, which yields nonidentical daughter cells that have only one set of chromosomes. II. Concept 12.2- The mitotic phase alternates with interphase in the cell cycle A. Phases of the Cell Cycle 1) The mitotic phase (M) phase, which includes both mitosis and cytokinesis, is usually the shortest part of the cell cycle. 2) Mitotic cell division alternates with a much longer stage called interphase, which often accounts for about 90% of the cell. It is during interphase that the cell grows and copies its chromosomes in preparation for cell division. 3) Interphase can be divided into subphases: * G1 phase (â€Å"first gap†) * S phase (â€Å"synthesis†) * G2 phase (â€Å"second gap†) 4) Mitosis is conventionally broken down into five stages: prophase, prometaphase, metaphase, anaphase, and telophase. B. The Mitotic Spindle 1) Many of the events in mitosis depend on the mitotic spindle, which begins to form in the cytoplasm during prophase. This structure consists of fibers made from microtubules and associated proteins. 2) In animal cells, the assembly of spindle microtubules starts at the centrosome, a subcellular region containing material that functions throughout the cell cycle to organize the cell’s microtubules. 3) An aster, a radial array of short microtubules. The spindle includes the centrosomes, the spindle microtubules, and the asters. 4) Each of the two sister chromatids of a replicated chromosome has a kinetochore, a structure of proteins associated with specific sections of chromosomal DNA at the centromere. 5) During prometaphase, the spindle microtubules attach to the kinetochores which then moves the chromosomes toward the pole from which those microtubules extend. 6) At metaphase, the centromeres of all the duplicated chromosome are on a plane midway between the spindle’s two poles. This plane is called the metaphase plate. C. Cytokinesis 1) Cytokinesis occurs by a process known as cleavage. The first sign of cleavage is the appearance of a cleavage furrow. 2) The contractile ring of actin microfilaments act as drawstrings. The cleavage furrow deepens, until the parent cell is split in two, creating two daughter cells. 3) In plant cells, vesicles from the Golgi apparatus move along microtubules to the middle of the cell, where they coalesce, producing a cell plate. D. Binary Fission 1) The asexual reproduction of single-celled eukaryotes includes mitosis and occurs by a type of cell division called binary fission, meaning â€Å"division in half†. 2) Prokaryotes also reproduce by binary fission, but the prokaryotic process does not involve mitosis. 3) In E. coli, the process of cell division is initiated when the DNA of the bacterial chromosome called the origin of replication, producing two origins. 4) The origin replicates while the other origin moves to the opposite end of the cell. The cell elongates and replication finishes and a new cell wall is deposited, which in result creates tow daughter cells. E. The Evolution of Mitosis 1) Since prokaryotes evolved before eukaryotes, mitosis may have evolved from binary fission. 2) Certain protists exhibit types of cell division that seem intermediate between binary fission and mitosis. III. Concept 12.3-The eukaryotic cell cycle is regulated by a molecular control system A. Evidence for Cytoplasmic Signals 1) Hypothesis: The cell cycle is driven by specific signaling molecules present in the cytoplasm 2) Evidence comes from an experiment where they induced cultured mammalian cells at different phases of the cell cycle to fuse. B. The Cell Cycle Control System 1) The sequential events of the cell cycle are directed by a distinct cell cycle control system, a cyclically operating set of molecules in the cell that both triggers and coordinates key events in the cell cycle. 2) A checkpoint in the cell cycle is a control point where stop and go-ahead signals can regulate the cycle (using signal transduction pathways). 3) If a cell receives a go-ahead signal at the G1 checkpoint, it will usually complete the G1, S, G2, and M phases and divide. 4) If it does not receive a go-ahead signal at that point, it will exit the cycle, switching into a nondividing state called the G0 phase. C. The Cell Cycle Clock: Cyclins and Cyclin Dependent Kinases 1) Rhythmic fluctuations in the abundance and activity if cell cycle control molecules pace the sequential events of the cell cycle. These regulatory molecules are mainly proteins of two types: protein kinases and cyclins. 2) Many of the kinases that drive the cell cycle are actually present at a constant concentration in the growing cell, but much of the time they are in inactive form. 3) To be active, such a kinase must be attached to a cyclin, a protein that gets its name from its cyclically fluctuating concentration in the cell. 4) Because of this requirement, these kinases are called cyclin-dependent kinases, or Cdks. 5) The activity of a Cdk fluctuates with changes in the concentration of its cyclin partner. 6) MPF (maturation-promoting factor) is a cyclin-Cdk complex that triggers a cell’s passage past the G2 checkpoint into the M phase D. Stop and Go Signs: Internal and External signals at the Checkpoints 1) An example of an internal signal is that kinetochores not attached to spindle microtubules send a molecular signal that delays anaphase 2) A growth factor is a protein released by certain cells that stimulates other cells to divide. 3) Different cell types respond specifically to different growth factors or combinations of growth factors. For example, platelet-derived frpwth factor stimulates the division of a human. 4) The effect of an external physical factor on cell division is clearly seen in density-dependent inhibition, a phenomenon in which crowded cells stop dividing. 5) Most animal cells also exhibit anchorage dependence. To divide the must be attached to a substratum, such as the inside of a culture jar or the extracellular matrix of a tissue. E. Loss of Cell Cycle Controls in Cancer Cells 1) Cancer cells do not heed the normal signals that regulate the cell cycle. They divide excessively and invade other tissues. In addition to their lack of density-dependent inhibition and anchorage dependence, cancer cells do not stop dividing when growth factors are depleted. 2) A logical hypothesis is that cancer cells do not need growth factors in their culture medium to grow and divide. 3) The problem of cancer begins when a single cell in a tissue undergoes transformation, the process that converts a normal cell to a cancer cell. The body’s immune system normally recognizes a transformed cell as an insurgent and destroys it. 4) If the abnormal cells remain at the original site, the lump is called a benign tumor. 5) In contrast, a malignant tumor becomes invasive enough to impair the function of one or more organs. These tumors can proliferate and spread to locations distant from their original site in a process called metastasis.

Christian Response to John Proctor and The Crucible :: Essay on The Crucible

The Crucible John Proctor is the protagonist in The Crucible. He becomes the person who fights for what is right. As the story goes on, the secrets of Proctor are revealed, and it is discovered that he committed adultery with Abigail Williams. In prison, before he is hanged, Proctor asks, â€Å"Who will judge me? God in Heaven, what is John Proctor, what is John Proctor?† John Proctor was a confused soul who discovered what he truly believed, and did not disobey what he decided to believe. As the play starts off, and John Proctor is introduced, it becomes know that he committed adultery with Abigail, the antagonist of the play. At this point, the play tells that John has gone against his own values by committing adultery, as well as the town’s values. He starts off seeming as though he is a very confused man and does not know what to think about his relationship with Abigail. â€Å"Abby, I may think of you softly from time to time. But I will cut off my hand before I’ll ever reach for you again.† (22). This is showing how he still likes her, but he feels he cannot commit adultery with her again. Nearing the end of The Crucible John Proctors position on his relationship has changed a good deal. He has realized how evil Abigail really is, and he has rejected their relationship. But now he must decide if he will lie about being a witch or not, and is questioning his wife on what to do. â€Å"Would you give them such a lie? Say it. Would you ever give them this? You would not, if tongs of fire were singeing you you would not! It is evil. Good, then it is evil, and I do it!† (128). At this point Proctor is unsure as to his position on whether or not he will lie an say he is a witch. Proctor’s values are being questioned. Will he lie and save his life, or die and tell the truth? On this question hinges the values and beliefs of John Proctor. As the play continues, John is still in prison, but is now signing the paper confessing he is a witch. Doing this will save his life, but it will be a lie. After he has signed this he realizes that this is horrible decision to make.

Fashion Film

Rules and Regulations As fashion film is a new addition to the fashion installment, there aren't any specific rules and regulations that the filmmakers have to follow because fashion is all about expressing opinions, feelings etc. However there are a few ethics that they should be aware of, with any film such as violence, drug abuse, discrimination etc. The filmmakers need to be aware of these ethics because the last thing you want the film to do is offend anyone because then the company, or in this case designer, could get a bad reputation and not become successful.Other things that should be considered when putting together a fashion show is the location because you want the show to be memorable to the audience and a unique location will help make it more memorable. The set is another important thing to think about because if there is a theme such as ‘nature' being carried out though the fashion then you'll want to back that up with a nature themed set; this will also make it more memorable to the audience.Seating should be considered because you want the audience to have a perfect view of the fashion and the film hat they will be seeing though out the show so that they can fully take in what they will be seeing. Lights are an important part of a fashion show because you want the catwalk to be lit up perfectly so the audience can see the clothes perfectly especially if there is any fine detail in the clothes.Music is something to consider because this can really add on to the theme of the show and create the sense of escapism that some audiences crave for; for example if there is a nature theme in your show then it could be a good idea to add some slow classic music with some wildlife sounds. The air and make up of the models is key to a fashion show because this can complete the look of the whole fashion show and really enhance the theme of the fashion show. One fashion show that really has been thought out to every detail is the Alexander Macaque show Homeowners SIS 10 in Paris.The title of the show was ‘Plat's Atlantis' and was inspired by concepts of environmental destruction, stem-cell technology, ‘mutation of the fittest' and the underwater kingdom of Atlantis. The location of this fashion show is unknown but it was performed in Paris during Fashion Week at the end of October 2010. I would hold my fashion show in Paris because it is considered the fashion capital of the world. Paris is a great place to hold a fashion show because the fashion history is so strong compared to other cities like London or Tokyo.The set of the fashion show consists of a very long, white, wide catwalk to represent a laboratory to expand the theme of Stem Cell Technology; there was also a 60 foot LED screen at the back to display the fashion film and two twenty foot robotic cameras along side of the catwalk where one of the cameras displayed the footage it was getting onto the giant screen. I really liked this set because it enhanced th e theme of a laboratory really well from the Petri dish like catwalk, the fashion on the models making them appear to be the experiments in the lab and the cameras acting like the scientists observing what was going on.The lighting used for this show was simple and even, this allowed the audience in the fashion show to see each outfit perfectly. This is a great way to install lights and I would defiantly use it in a fashion show because it doesn't take the attention of the viewers away from the fashion. The music for this fashion show sounds like it would e played in an opening scene for a blockbuster movie set underwater; it contains a lot of heavy synchs and long slow drums.I like this music and would use it in a fashion show because it adds to the theme of the show ‘Atlantis' and gives the audience a sense of escapism. To be able to broadcast my fashion film with music, I need to follow the rules set by The I-J Copyright Service. The law set by them states 1. Using the work of others If you use samples of music by other authors in your work, ensure that you get permission to use the work before you attempt to publish or sell your work. Similarly, f you use loops or samples available via sample collections etc. Ensure that these are licensed as free to use, or obtain permission first. 2. Obtaining permission If you need to get permission to use a piece of music, normally the best place to start is with the last know publisher for the work. They will certainly know how to get permission to use the work, (as they must have permission themselves), so they will certainly know who you would need to contact. If the work is by an U. S. Artist, you could contact the American Society of Composers, Authors and Publishers, IBM (Broadcast Music, IncBand members agreements Where music is written as a group effort, we recommend that you draw up an agreement to clarify issues, such as which rights belong to which member, and how royalties would be distributed in the event that members of your group leave. For successful commercial bands, incorporation is also an option. As with a normal incorporated company, the band members would own shares in the band/company. In this situation, a band member would typically sell his shares to the other members if he decided to leave. This states that I need to obtain permission by the DC/Producer that produced this song.

Learn About the Sixth Amendment Trial by Jury

The Sixth Amendment to the United States Constitution ensures certain rights of individuals facing prosecution for criminal acts. While it is previously mentioned in Article III, Section 2 of the Constitution, the Sixth Amendment is popularly recognized as the source of the right to a timely public trial by jury. As one of the original 12 amendments proposed in the Bill of Rights, the Sixth Amendment was submitted to the then 13 states for ratification on September 5, 1789, and approved by the required nine states on December 15, 1791. The full text of the Sixth Amendment states: In all criminal prosecutions, the accused shall enjoy the right to a speedy and public trial, by an impartial jury of the State and district wherein the crime shall have been committed, which district shall have been previously ascertained by law, and to be informed of the nature and cause of the accusation; to be confronted with the witnesses against him; to have compulsory process for obtaining witnesses in his favor, and to have the Assistance of Counsel for his defence. Specific rights of criminal defendants ensured by the Sixth Amendment include: The right to a public trial held without unnecessary delay. Often referred to as a â€Å"speedy trial.†The right to be represented by a lawyer if desired.The right to be tried by an impartial jury.The right of the accused to obtain and present witnesses to appear on their behalf.The right of the accused to â€Å"confront,† or question witnesses against them.The right of the accused to be informed of the identity of their accusers and the nature of the charges and evidence to be used against them. Similar to other constitutionally-ensured rights related to the criminal justice system, the Supreme Court has ruled that the protections of the Sixth Amendment apply in all states under the principle of â€Å"due process of law† established by the Fourteenth Amendment. Legal challenges to the provisions of the Sixth Amendment occur most often in cases involving the fair selection of jurors, and the need to protect the identity of witnesses, like victims of sex crimes and persons in danger of possible retaliation as a result of their testimony. The Courts Interpret the Sixth Amendment While the mere 81 words of the Sixth Amendment establish the basic rights of persons facing prosecution for criminal acts, sweeping changes in society since 1791 have forced the federal courts to consider and define exactly how some of those most visible basic rights should be applied today. Right to a Speedy Trial Exactly what does â€Å"speedy† mean? In the 1972 case of Barker v. Wingo, the Supreme Court established four factors for deciding whether a defendants speedy trial right had been violated. Length of the delay: A delay of one year or longer from the date of the defendant’s arrest or indictment, whichever happens first, was termed to be â€Å"presumptively prejudicial,† However, the Court did not establish one-year as an absolute time limitCause of the delay: While trials may not be excessively delayed solely to disadvantage the defendant, they may be delayed in order to secure the presence of absent or reluctant witnesses or for other practical considerations, such as change of trial location, or â€Å"venue.†Did the defendant agree to the delay? Defendants who agree to delays that work in their benefit may not later claim that the delay had violated their rights.The degree to which the delay may have prejudiced the court against the defendant. One year later, in the 1973 case of Strunk v. United States, the Supreme Court ruled that when an appeals court finds that a defendants right to a speedy trial was violated, the indictment must be dismissed and/or the conviction overturned. Right to Trial by Jury In the United States, the right to be tried by a jury has always depended on the seriousness of the criminal act involved. In â€Å"petty† offenses — those punishable by no more than six months in jail — right to a jury trial does apply. Instead, decisions can be rendered and punishments assessed directly by judges. For example, most cases heard in municipal courts, such as traffic violations and shoplifting are decided solely by the judge. Even in cases of multiple petty offenses by the same defendant, for which the total time in jail might exceeding six months, the absolute right to a jury trial does not exist. In addition, minors are typically tried in juvenile courts, in which defendants may be given reduced sentences, but forfeit their right to a jury trial. Right to a Public Trial The right to a public trial is not absolute. In the 1966 case of Sheppard v. Maxwell, involving the murder of the wife of Dr. Sam Sheppard, a popular high-profile neurosurgeon, the Supreme Court held that public access to trials can be restricted if, in the opinion of the trial judge,excess publicity might harm the defendants right to a fair trial. Right to an Impartial Jury The courts have interpreted the Sixth Amendment’s guarantee of impartiality to mean that individual jurors must be able to act without being influenced by personal bias. During the jury selection process, lawyers for both sides are allowed to question potential jurors to determine whether they harbor any bias for or against the defendant. If such bias is suspected, the lawyer may challenge the juror’s qualification to serve. Should the trial judge determine the challenge to be valid, the potential juror will be dismissed. In the 2017 case of Peà ±a-Rodriguez v. Colorado, the Supreme Court ruled that the Sixth Amendment requires criminal courts to investigate all claims by defendants that their jurys guilty verdict was based on racial bias. In order for a guilty verdict to be overturned, the defendant must prove that the racial bias â€Å"was a significant motivating factor in the jurors vote to convict.† Right to Proper Trial Venue Through a right known in legal language as â€Å"vicinage,† the Sixth Amendment requires that criminal defendants be tried by jurors chosen from legally determined judicial districts. Over time, the courts have interpreted this to mean that selected jurors must reside in the same state in which the crime was committed and charges were filed. In the 1904 case of Beavers v. Henkel, the Supreme Court ruled that the location where the alleged crime took place determines the location of the trial. In cases where the crime may have occurred in multiple states or judicial districts, the trial may be held in any of them. In rare cases of crimes that take place outside the United States, like crimes at sea, the U.S. Congress may set the location of the trial. Factors Driving the Sixth Amendment As the delegates to the Constitutional Convention sat down to craft the Constitution in the spring of 1787, the U.S. criminal justice system was best described as a disorganized â€Å"do-it-yourself† affair. Without professional police forces, ordinary untrained citizens served in loosely defined roles as sheriffs, constables, or night watchmen. It was almost always up to victims themselves to charge and prosecute criminal offenders. Lacking an organized government prosecutorial process, trials often devolved into shouting matches, with both victims and defendants representing themselves. As a result, trials involving even the most serious crimes lasted only minutes or hours instead of days or weeks. Juries of the day were made up of twelve ordinary citizens — typically all men — who often knew the victim, defendant, or both, as well as the details of the crime involved. In many cases, most of the jurors had already formed opinions of guilt or innocence and were unlikely to be swayed by evidence or testimony. While they were informed of which crimes were punishable by the death penalty, jurors received few if any instructions from judges. Jurors were allowed and even urged to directly question witnesses and to publically debate the defendant’s guilt or innocence in open court. It was in this chaotic scenario that the framers of the Sixth Amendment sought to ensure that the processes of the American criminal justice system were conducted impartially and in the best interest of the community, while also protecting the rights of both the accused and victims. Sixth Amendment Key Takeaways The Sixth Amendment to the U.S. Constitution is one of the original articles of the Bill of Right and was ratified on December 15, 1791.The Sixth Amendment protects the rights of persons facing prosecution for criminal acts.Also known as the â€Å"Speedy Trial Clause,† the Sixth Amendment establishes the rights of defendants to be given a fair and speedy public trial before a jury, to have a lawyer, to be informed of the charges against them, and to question witnesses against them.The courts continue to interpret the Sixth Amendment as needed to respond to developing social issues such as racial discrimination.The Sixth Amendment applies in all states under the principle of â€Å"due process of law† established by the Fourteenth Amendment.The Sixth Amendment was created to correct the inequities of the disorganized, chaotic criminal justice system prevailing at the time.