The Difference Between Mitosis and Meiosis

The Difference Between Mitosis and Meiosis Mitosis vs Meiosis Organisms grow and reproduce through cell division. In eukaryotic cells, the production of new cells occurs as a result of mitosis and meiosis. These two nuclear division processes are similar but distinct. Both processes involve the division of a diploid cell, or a cell containing two sets of chromosomes (one chromosome donated from each parent). In mitosis, the genetic material (DNA) in a cell is duplicated and divided equally between two cells. The dividing cell goes through an ordered series of events called the cell cycle. The mitotic cell cycle is initiated by the presence of certain growth factors or other signals that indicate that the production of new cells is needed. Somatic cells of the body replicate by mitosis. Examples of somatic cells include fat cells, blood cells, skin cells, or any body cell that is not a sex cell. Mitosis is necessary to replace dead cells, damaged cells, or cells that have short life spans. Meiosis is the process by which gametes (sex cells) are generated in organisms that reproduce sexually. Gametes are produced in male and female gonads  and  contain one-half the number of chromosomes as the original cell. New gene combinations are introduced in a population through the genetic recombination that occurs during meiosis. Thus, unlike the two genetically identical cells produced in mitosis, the meiotic cell cycle produces four cells that are genetically different. Key Takeaways: Mitosis vs Meiosis Mitosis and meiosis are nuclear division processes that occur during cell division.Mitosis involves the division of body cells, while meiosis involves the division of sex cells.The division of a cell occurs once in mitosis but twice in meiosis.Two daughter cells are produced after mitosis and cytoplasmic division, while four daughter cells are produced after meiosis.Daughter cells resulting from mitosis are diploid, while those resulting from meiosis are haploid.Daughter cells that are the product of mitosis are genetically identical. Daughter cells produced after meiosis are genetically diverse.Tetrad formation occurs in meiosis but not mitosis. Differences Between Mitosis and Meiosis Lily Anther Microsporocyte in Telophase II of Meiosis. Ed Reschke/Photolibrary/Getty Images 1. Cell Division Mitosis: A somatic cell divides once. Cytokinesis (the division of the cytoplasm) occurs at the end of telophase.Meiosis: A reproductive cell divides twice. Cytokinesis happens at the end of telophase I and telophase II. 2. Daughter Cell Number Mitosis: Two daughter cells are produced. Each cell is diploid containing the same number of chromosomes.Meiosis: Four daughter cells are produced. Each cell is haploid containing one-half the number of chromosomes as the original cell. 3. Genetic Composition Mitosis: The resulting daughter cells in mitosis are genetic clones (they are genetically identical). No recombination or crossing over occur.Meiosis: The resulting daughter cells contain different combinations of genes. Genetic recombination occurs as a result of the random segregation of homologous chromosomes into different cells and by the process of crossing over (transfer of genes between homologous chromosomes). 4. Length of Prophase Mitosis: During the first mitotic stage, known as prophase, chromatin condenses into discrete chromosomes, the nuclear envelope breaks down, and spindle fibers form at opposite poles of the cell. A cell spends less time in prophase of mitosis than  a cell  in prophase I of meiosis.Meiosis: Prophase I consists of five stages and lasts longer than prophase of mitosis. The five stages of meiotic prophase I are leptotene, zygotene, pachytene, diplotene, and diakinesis. These five stages do not occur in mitosis. Genetic recombination and crossing over take place during prophase I. 5. Tetrad Formation Mitosis: Tetrad formation does not occur.Meiosis: In prophase I, pairs of homologous chromosomes line up closely together forming what is called a tetrad. A tetrad consists of four chromatids (two sets of sister chromatids). 6. Chromosome Alignment in Metaphase Mitosis: Sister chromatids (duplicated chromosome comprised of two identical chromosomes connected at the centromere region) align at the metaphase plate (a plane that is equally distant from the two cell poles).Meiosis: Tetrads (homologous chromosome pairs) align at the metaphase plate in metaphase I. 7. Chromosome Separation Mitosis: During anaphase, sister chromatids separate and begin migrating centromere first toward opposite poles of the cell. A separated sister chromatid becomes known as daughter chromosome and is considered a full chromosome.Meiosis: Homologous chromosomes migrate toward opposite poles of the cell during anaphase I. Sister chromatids do not separate in anaphase I. Mitosis and Meiosis Similarities Plant cell in Interphase. In interphase, the cell is not undergoing cell division. The nucleus and chromatin are evident. Ed Reschke/Getty Images While the processes of mitosis and meiosis contain a number of differences, they are also similar in many ways. Both processes have a growth period called interphase, in which a cell replicates its genetic material and organelles in preparation for division. Both mitosis and meiosis involve phases: Prophase, Metaphase, Anaphase and Telophase. Although in meiosis, a cell goes through these cell cycle phases twice. Both processes also involve the lining up of individual duplicated chromosomes, known as sister chromatids, along the metaphase plate. This happens in metaphase of mitosis and metaphase II of meiosis. In addition, both mitosis and meiosis involve the separation of sister chromatids and the formation of daughter chromosomes. This event occurs in anaphase of mitosis and anaphase II of meiosis. Finally, both processes end with the division of the cytoplasm that produces individual cells.

Battle of Guadalcanal in World War II

Battle of Guadalcanal in World War II Battle of Guadalcanal Conflict Date The Battle of Guadalcanal began on August 7, 1942, during World War II (1939-1945). Armies Commanders Allies Major General Alexander Vandergrift Major General Alexander Patchup to 60,000 men Japanese Lieutenant General Harukichi Hyakutake General Hitoshi Imamura rising to 36,200 men Operation Watchtower In the months after the attack on Pearl Harbor, Allied forces suffered a string of reverses as Hong Kong, Singapore, and the Philippines were lost and the Japanese swept through the Pacific. Following the propaganda victory of the Doolittle Raid, the Allies succeeded in checking the advance of the Japanese at the Battle of the Coral Sea. The following month they won a decisive victory at the  Battle of Midway which saw four Japanese carriers sunk in exchange for USS Yorktown (CV-5). Capitalizing on this triumph, the Allies began to move to the offensive in the summer of 1942. Conceived by Admiral Ernest King, Commander-in-Chief, US Fleet, Operation Watchtower called for Allied troops to land in the Solomon Islands at Tulagi, Gavutu–Tanambogo, and Guadalcanal. Such an operation would protect the Allied lines of communication to Australia and allow for the capture of a Japanese airfield then under construction at Lunga Point, Guadalcanal. To oversee the operation, the South Pacific Area was created with Vice Admiral Robert Ghormley in command and reporting to Admiral Chester Nimitz at Pearl Harbor. The ground forces for the invasion would be under the leadership of Major General Alexander A. Vandegrift, with his 1st Marine Division forming the bulk of the 16,000 troops involved. In preparation for the operation, Vandegrifts men were shifted from the United States to New Zealand and forward bases were established or reinforced in the New Hebrides and New Caledonia. Assembling near Fiji on July 26, the Watchtower force consisted of 75 ships led by Vice Admiral Frank J. Fletcher with Rear Admiral Richmond K. Turner overseeing the amphibious forces. Going Ashore Approaching the area in poor weather, the Allied fleet remained undetected by the Japanese. On August 7, the landings began with 3,000 Marines assaulting the seaplane bases at Tulagi and Gavutu-Tanambogo. Centered on Lieutenant Colonel Merritt A. Edsons 1st Marine Raider Battalion and the 2nd Battalion, 5th Marines, the Tulagi force was compelled to disembark approximately 100 yards from the beach due to submerged coral reefs.   Wading ashore against no resistance, the Marines began securing the island and engaged enemy forces led by Captain Shigetoshi Miyazaki. Though Japanese resistance was fierce on both Tulagi and Gavutu-Tanambogo, the islands were secured on August 8 and 9 respectively. The situation on Guadalcanal was different as Vandegrift landed with 11,000 men against minimal opposition. Pushing forward the next day, they advanced to the Lunga River, secured the airfield, and drove off the Japanese construction troops that were in the area. The Japanese retreated west to the Matanikau River. In their haste to retreat, they left behind large quantities of food and construction equipment. At sea, Fletchers carrier aircraft incurred losses as they battled Japanese land-based aircraft from Rabaul. These attacks also resulted in the sinking of a transport, USS George F. Elliott, and a destroyer, USS Jarvis. Concerned about aircraft losses and his ships fuel supplies, he withdrew from the area on the evening of August 8. That evening, Allied naval forces suffered a severe defeat at the nearby Battle of Savo Island. Caught by surprise,  Rear Admiral Victor Crutchley screening force lost four heavy cruisers. Unaware that Fletcher was withdrawing, the Japanese commander, Vice Admiral Gunichi Mikawa, departed the area after the victory fearing air attack once the sun rose   His air cover gone, Turner withdrew on August 9 despite the fact that not all of the troops and supplies had been landed (Map). The Battle Begins Ashore, Vandegrifts men worked to form a loose perimeter and completed the airfield on August 18. Dubbed Henderson Field in memory of Marine aviator Lofton Henderson who had been killed at Midway, it began receiving aircraft two days later. Critical to the islands defense, the aircraft at Henderson became known as the Cactus Air Force (CAF) in reference to Guadalcanals code name. Short on supplies, the Marines initially possessed about two weeks worth of food when Turner departed. Their situation was further worsened by the onset of dysentery and a variety of tropical diseases. During this time, the Marines began patrolling against the Japanese in the Matanikau Valley with mixed results. In response to the Allied landings, Lieutenant General Harukichi Hyakutake, commander of the 17th Army at Rabaul, began shifting troops to the island. The first of these, under Colonel Kiyonao Ichiki, landed at Taivu Point on August 19. Advancing west, they attacked the Marines early on August 21 and were repulsed with heavy losses at the Battle of the Tenaru. The Japanese directed additional reinforcements to the area which resulted in the Battle of the Eastern Solomons. Though the battle was a draw, it forced Rear Admiral Raizo Tanakas reinforcement convoy to turn back. As the CAF controlled the skies around the island during daylight hours, the Japanese were compelled to deliver supplies and troops to the island using destroyers. Holding Guadalcanal Fast enough to reach the island, unload, and escape before dawn, the destroyer supply line was dubbed the Tokyo Express. Though effective, this method precluded the delivery of heavy equipment and weapons. His troops suffering from tropical diseases and food shortages, Vandegrift was reinforced and re-supplied in late-August and early-September. Having built up sufficient strength, Major General Kiyotake Kawaguchi attacked the Allied position at Lunga Ridge, south of Henderson Field, on September 12. In two nights of brutal fighting, the Marines held, forcing the Japanese to retreat. On September 18, Vandegrift was further reinforced, though the carrier USS Wasp was sunk covering the convoy. An American thrust against the Matanikau was checked late in the month, but actions in early October inflicted heavy losses on the Japanese and delayed their next offensive against the Lunga perimeter. With the struggle raging, Ghormley was convinced to dispatch US Army troops to aid Vandegrift. This coincided with a large Express run scheduled for October 10/11. On that evening, the two forces collided and Rear Admiral Norman Scott won a victory at the Battle of Cape Esperance. Not to be deterred, the Japanese sent a large convoy towards the island on October 13. To provide cover, Admiral Isoroku Yamamoto dispatched two battleships to bombard Henderson Field. Arriving after midnight on October 14, they succeeded in destroying 48 of CAFs 90 aircraft. Replacements were quickly flown to the island and CAF began attacks on the convoy that day but to no effect. Reaching Tassafaronga on the islands western shore, the convoy began unloading the next day. Returning, CAF aircraft were more successful, destroying three cargo ships. Despite their efforts, 4,500 Japanese troops landed. The Battle Grinds On Reinforced, Hyakutake had around 20,000 men on Guadalcanal. He believed Allied strength to be around 10,000 (it was actually 23,000) and moved forward with another offensive. Moving east, his men assaulted the Lunga Perimeter for three days between October 23-26. Dubbed the Battle of Henderson Field, his attacks were thrown back with massive losses numbering 2,200-3,000 killed against less than 100 Americans. As the fighting was concluding, American naval forces now led by Vice Admiral William Bull Halsey (Ghormley was relieved on October 18) engaged the Japanese at the Battle of the Santa Cruz Islands. Though Halsey lost the carrier USS Hornet, his men inflicted severe losses on the Japanese aircrews. The fight marked the last time that either sides carriers would clash in the campaign. Exploiting the victory at Henderson Field, Vandegrift began an offensive across the Matanikau. Though initially successful, it was halted when Japanese forces were discovered to the east near Koli Point. In a series of battles around Koli in early November, American forces defeated and drove off the Japanese. As this action was underway, two companies of the 2nd Marine Raider Battalion under Lieutenant Colonel Evans Carlson landed at Aola Bay on November 4. The next day, Carlson was ordered to move overland back to Lunga (approx. 40 miles) and engage enemy forces along the way. During the Long Patrol, his men killed around 500 Japanese. At Matanikau, Tokyo Express runs aided Hyakutake in strengthening his position and turning back American attacks on November 10 and 18. Victory at Last As a stalemate ensued on land, the Japanese made efforts to build up strength for an offensive in late November. To aid in this, Yamamoto made available eleven transports for Tanaka to transport 7,000 men to the island. This convoy would be covered by a force including two battleships which would bombard Henderson Field and destroy the CAF. Aware that the Japanese were moving troops to the island, the Allies planned a similar move. On the night of November 12/13, the Allied covering force encountered the Japanese battleships in the opening actions of the Naval Battle of Guadalcanal. Taking off on November 14, CAF and aircraft from USS Enterprise spotted and sunk seven of Tanakas transports. Though taking heavy losses the first night, American warships turned the tide on the night of November 14/15. Tanakas remaining four transports beached themselves at Tassafaronga before dawn, but were quickly destroyed by Allied aircraft. The failure to reinforce the island led to the abandonment of the November offensive. On November 26, Lieutenant General Hitoshi Imamura took command of the newly created Eighth Area Army at Rabaul which included Hyakutakes command. Though he initially began planning for attacks at Lunga, the Allied offensive against Buna on New Guinea led to a shift in priorities as it presented a greater threat to Rabaul. As result, offensive operations on Guadalcanal were suspended. Though the Japanese won a naval victory at Tassafaronga on November 30, the supply situation on the island was becoming desperate. On December 12, the Imperial Japanese Navy recommended that the island be abandoned. The army concurred and on December 31 the Emperor endorsed the decision. As the Japanese planned their withdraw, changes occurred on Guadalcanal with Vandegrift and the battle weary 1st Marine Division departing and Major General Alexander Patchs XIV Corps taking over. On December 18, Patch began an offensive against Mount Austen. This stalled on January 4, 1943 due to strong enemy defenses. The attack was renewed on January 10 with troops also striking ridges known as the Seahorse and the Galloping Horse. By January 23, all objectives had been secured. As this fight was concluding, the Japanese had begun their evacuation which was dubbed Operation Ke. Unsure of Japanese intentions, Halsey sent Patch reinforcements which led to the naval Battle of Rennell Island on January 29/30. Concerned about a Japanese offensive, Patch did not aggressively pursue the retreating enemy. By February 7, Operation Ke was complete with 10,652 Japanese soldiers having left the island. Realizing the enemy had departed, Patch declared the island secured on February 9. Aftermath During the campaign to take Guadalcanal, the Allied losses numbered around 7,100 men, 29 ships, and 615 aircraft. Japanese casualties were approximately 31,000 killed, 1,000 captured, 38 ships, and 683-880 aircraft. With the victory at Guadalcanal, the strategic initiative passed to the Allies for the remainder of the war. The island was subsequently developed into a major base for supporting future Allied offensives. Having exhausted themselves in the campaign for the island, the Japanese had weakened themselves elsewhere which contributed to the successful conclusion of Allied campaigns on New Guinea. The first sustained Allied campaign in the Pacific, it provided a psychological boost for the troops as well as led to the development of combat and logistical systems that would be used in the Allies march across the Pacific. With the island secured, operations continued on New Guinea and the Allies began their island hopping campaign towards Japan.

Security Incident Case Study Essay Example | Topics and Well Written Essays - 250 words

Security Incident Case Study - Essay Example This paper seeks to describe how effectively an emergency incident that occurred in Los Angeles International Airport (LAX), at 2:38pm, Terminal 4, would have be managed and highlight how effective airport operators can be, when during emergencies. In this case, where a man trespasses through a restricted doorway, there is actually no need for the crew to lower security gates and order out everyone off the secured gate including the passengers who are already aboard waiting to depart. Since it’s a breech that is only confined to a limited space, the best thing to do would be; assuming that the cameras in that terminal are working, trail the person in question quietly and swiftly without drawing unnecessary attention from the other parties. The evacuation process is so hectic and time consuming; and one that would literally paralyse operations throughout the entire airport. In addition; and as observed in our case study, it is more likely to cause a lot of panic and confusion, in turn making the whole process of trailing the individual in question futile. Finally, given that people will be aware of an anomaly happening at the airport; it is more likely to trigger unexpected reactions. People may start running and in the process injure each other. In conclusion, as analysed in the paper, as an airport operator, your duty is not to bring about confusion and add complexity to arising problems. With this case, and other emergency issues that arise, it is the airport’s duty to ensure that the safety of everyone is guaranteed and the simplest method is used in combating any possible

Gandhi (1982) Movie analysis not review attempt to dissect the films Essay

Gandhi (1982) Movie analysis not review attempt to dissect the films approach to its historical matter - Essay Example The opening statement of the film, – "No mans life can be encompassed in one telling. There is no way to give each year its allotted weight, to include each event, each person who helped to shape a lifetime. What can be done is to be faithful in spirit to the record and try to find ones way to the heart of the man" – shows the respect of Attenborough to Gandhi and a glimpse to the way he is going to present Gandhi’s legendary freedom movement. The director resorts to a flash back mode in this film. After portraying the last episodes in Gandhi’s life, he then moves on to sketch the life of Gandhi as a young barrister in Africa. Gandhi faces the first bitter experience here in Africa while travelling in the first class train compartment. Though he possessed the reservation ticket, he was thrown out of the train due to the fact that the first class is reserved for the Europeans. He had to spend the whole night on the cold railway station platform and realized that such humiliations and discriminations are quite common in Africa and therefore he decides to retaliate against it. He says, â€Å"We are children of God and members of the Empire.† This incident acts as a stimulus for Gandhi to conduct various protests against social injustices. The film then shows Gandhi’s return to India after having some success in his endeavors. The Indian National Congress party welcomed Gandhi to India and insisted him to travel through the country and identify the real suffering of the ordinary people. After witnessing them, he continues his protestations against injustices in India where is treated as a national hero. But things were not easy for Gandhi as he had to confront with many problems from the British Empire. The film links the important incidents in Gandhi’s life. Gandhi is often jailed as a result of his disagreement with the British authority on several matters. He goes on a hunger strike in order to react against the

Capstone Essay Example | Topics and Well Written Essays - 2000 words - 8

Capstone - Essay Example This paper also provides information concerning the ethical values of the company, and how it affects the organizations bottom line. Northrop Grumman is an American Multi-national company, specializing in the production of defense and aerospace facilities/ products. The company began its operations in 1994, through an acquisition of Northrop by Grumman. As of the year 2010, this company was voted as the fourth largest defense contractor in the world, and it employs more than 68,000 employees all over the world. The mission of the company is to be a leader in the production of defense and aeronautical technology. The mission of the company is also to satisfy the various needs of its customers through delivery and innovating high quality technological products, which are affordable (Hayden, Campbell and Cummins, 2010). The vision of the company on the other hand is to be a trusted and reliable supplier and producer of technologies and systems capable of protecting the country. To achieve this objective, the company aims to observe ethical values that guide defense contracting, promote innovation and collaboration a mongst its employees and key stakeholders. The key stakeholders of Northrop Grumman are share holders, suppliers, employees, and the company’s customers, which are always security institutions of America, and American allies. These people have an impact on the general performance of the company; this is because the company aims at achieving profitability for purposes of satisfying its shareholders and customers (Hayden, Campbell and Cummins, 2010). The company also seeks to produce high quality defense technologies, for purposes of protecting the country and satisfying the needs of its customers. Production of high quality defense technology is part and parcel of the organization’s mission and vision, and hence the employees of the

Strategic Choice and Evaluation Paper on Apple Inc Research

Strategic Choice and Evaluation on Apple Inc - Research Paper Example In this sense, the company cannot afford to relent on its path towards market domination because its rivals and new entrants can easily catch up and take over the market leadership position that Apple Inc. currently enjoys. This paper explores the three levels of strategy that the company can use to consolidate its position. The three areas of strategy include the identification of the best value discipline for the company, the best generic strategy option, and the most effective grand strategy that Apple Inc. ought to pursue. Value Discipline All companies usually choose between three broad value disciplines. This three value disciplines are operational efficiency, product leadership, and customer intimacy (Treacy & Wiersema, 1993). Operational efficiency refers to the ability of a company to provide a product without hassles and with minimal inconvenience to the customer. Usually, it calls for investment in powerful supply-chain management tools to ensure that there are no delays i n the production process. Companies that attain efficient operations as a value discipline also tend to provide basic products made with little or no embellishments, and with a very small parts-count. They employ advanced levels of designed-for -manufacture concepts. In order to attain product leadership as a value discipline, a company must invest in advanced product research and development techniques because it requires that the company retain leadership in its ability provide new products for its customers (Treacy & Wiersema, 1993). The IT industry seems to require this as a basic value discipline because of the high rate of innovation in the industry. The amount of game-changing discoveries in the IT industry renders new products obsolete within a very short time. Thirdly, adopting customer intimacy as a value discipline calls for the use of personalized methods of production and marketing that aims at developing a sense of personal attachment with customers (Treacy & Wiersema, 1993). This approach works best for low volume and high margin products for the target market. The best value discipline for Apple Inc. is product innovation. This comes from the fact that Apple Inc. is an IT based industry dealing with personal products. The main competitive edge for companies producing IT devices for personal use is in the innovativeness of the products. Pursuing operational efficiency will limit the innovative edge that Apple Inc. enjoys because of the efforts it will divert to attain efficiency. On the other hand, Apple Inc. develops products for the mass market. It is very challenging to implement customer intimacy as a value discipline when it comes to productions for the mass market. However, there may be strategic benefits in pursuing a two-fold strategy both as a product leader and as an efficiency operator because Apple Inc. may not always be a product leader in the unpredictable IT industry. Product Innovation alone may also make it too expensive for App le Inc. to return a profit because of the high cost of product development. Generic Strategy Porter identified three elements of generic strategy that informs the approaches organizations use to gain market share. In Porters model, the three strategies come from a matrix developed by comparing the scope of the target market with the source of advantage (Porter, 1980). In this sense, a company can pursue a strategy aiming for a niche market or for the mass market. In addition, it has to make a decision regarding whether it

The Pros & Cons of In-House Versus Outsourced R&D Activity for Assignment

The Pros & Cons of In-House Versus Outsourced R&D Activity for Technology Firms - Assignment Example This research will begin with the statement that there is recent evidence showing that firms no longer depend entirely on in-house R&D to maintain their technological competitiveness. This development, in as much as it has been contended, in portions reflects technological and economical globalization, whereby there is an increasing correspondence in categories of technologies across countries of harmony. Consequently, cross border competition is growing which has resulted in fewer opportunities for profits despite higher costs in retaining technological resources to remain internationally competitive. On the other hand, there is evidence that outsourcing research and development (R&D) activities are on the increase too, for instance in the R&D Magazine January 2001 Issue reports according to a survey of the people reading, a significant portion of the total R&D would be outsourced. The term non – internal is a premeditated one and is proposed to comprise of both outer activit ies (arms-length relationships that include licensing, R&D contracts, outsourcing and other customer supplier relationships) and quasi-external activity like strategic alliances which is said to involve a good number of organizational methods. Non- internal activities are advantageous as they are a ‘reversible’ asset as well as benefits of exploring new areas prompting radical transformation. The funds needed are smaller and the dangers are to a great extent reduced and, in case of the organizational predicament of failure, the limited damage is imposed on primary operations of the firm.