Meiosis is a special type of cell division used by sexually-reproducing organisms to produce the gametes, such as sperm or egg cells. It involves two rounds of division that result in four cells with only one copy of each chromosome. Additionally, prior to the division, genetic material from the paternal and maternal copies of each chromosome is crossed over, creating new combinations of code on each chromosome. On, during fertilisation, the haploid cells produced by meiosis from a male and female will fuse to create a cell with two copies of each chromosome again, the zygote. Errors in meiosis resulting in aneuploidy are the leading known cause of miscarriage and the most frequent genetic cause of developmental disabilities. In meiosis, DNA replication is followed by two rounds of cell division to produce four daughter cells, each with half the number of chromosomes as the original parent cell; the two meiotic divisions are known as meiosis I and meiosis II. Before meiosis begins, during S phase of the cell cycle, the DNA of each chromosome is replicated so that it consists of two identical sister chromatids, which remain held together through sister chromatid cohesion.
This S-phase can be referred to as "premeiotic S-phase" or "meiotic S-phase". Following DNA replication, meiotic cells enter a prolonged G2-like stage known as meiotic prophase. During this time, homologous chromosomes pair with each other and undergo genetic recombination, a programmed process in which DNA may be cut and repaired, which allows them to exchange some of their genetic information. A subset of recombination events results in crossovers, which create physical links known as chiasmata between the homologous chromosomes. In most organisms, these links can help direct each pair of homologous chromosomes to segregate away from each other during Meiosis I, resulting in two haploid cells that have half the number of chromosomes as the parent cell. During meiosis II, the cohesion between sister chromatids is released and they segregate from one another, as during mitosis. In some cases, all four of the meiotic products form gametes such as sperm, spores or pollen. In female animals, three of the four meiotic products are eliminated by extrusion into polar bodies, only one cell develops to produce an ovum.
Because the number of chromosomes is halved during meiosis, gametes can fuse to form a diploid zygote that contains two copies of each chromosome, one from each parent. Thus, alternating cycles of meiosis and fertilization enable sexual reproduction, with successive generations maintaining the same number of chromosomes. For example, diploid human cells contain 23 pairs of chromosomes including 1 pair of sex chromosomes, half of maternal origin and half of paternal origin. Meiosis produces haploid gametes; when two gametes fuse, the resulting zygote is once again diploid, with the mother and father each contributing 23 chromosomes. This same pattern, but not the same number of chromosomes, occurs in all organisms that utilize meiosis. Meiosis occurs in all sexually-reproducing single-celled and multicellular organisms, including animals and fungi, it is an essential process for spermatogenesis. Although the process of meiosis is related to the more general cell division process of mitosis, it differs in two important respects: Meiosis begins with a diploid cell, which contains two copies of each chromosome, termed homologs.
First, the cell undergoes DNA replication, so each homolog now consists of two identical sister chromatids. Each set of homologs pair with each other and exchange genetic information by homologous recombination leading to physical connections between the homologs. In the first meiotic division, the homologs are segregated to separate daughter cells by the spindle apparatus; the cells proceed to a second division without an intervening round of DNA replication. The sister chromatids are segregated to separate daughter cells to produce a total of four haploid cells. Female animals employ a slight variation on this pattern and produce one large ovum and two small polar bodies; because of recombination, an individual chromatid can consist of a new combination of maternal and paternal genetic information, resulting in offspring that are genetically distinct from either parent. Furthermore, an individual gamete can include an assortment of maternal and recombinant chromatids; this genetic diversity resulting from sexual reproduction contributes to the variation in traits upon which natural selection can act.
Meiosis uses many of the same mechanisms as mitosis, the type of cell division used by eukaryotes to divide one cell into two identical daughter cells. In some plants and protists meiosis results in the formation of spores: haploid cells that can divide vegetatively without undergoing fertilization; some eukaryotes, like bdelloid rotifers, do not have the ability to carry out meiosis and have acquired the ability to reproduce by parthenogenesis. Meiosis does not occur in archaea or bacteria, which reproduce asexually via binary fission. However, a "sexual" process known as horizontal gene transfer involves the transfer of DNA from one bacterium or archaeon to another and recombination of these DNA molecules of different parental origin. Meiosis was discovered and described for the first time in sea urchin eggs in 1876 by the German biologist Oscar Hertwig, it was described again in 1883, at the level of chromosomes, by the Belgian zoologist Edouard Van Beneden, in Ascaris roundworm
Appu Kuttan, is an Indian American philanthropist, consultant and the founder and chairman of the National Education Foundation, a global non-profit organization, founded in 1989. His philanthropic efforts include the distribution of over a million top-rated individualized courses at drastically reduced rates to public schools and colleges, he is the developer of Management By Cyberlearning. Prompted by a conversation with Gordon Moore of Intel and President Bill Clinton, Kuttan is credited for coining the term'cyberlearning' long before its popular use, he has written several highly rated books and articles, including Happy Executive — A Systems Approach. He has served as an advisor to several national leaders including President Bill Clinton, India Prime Minister Rajiv Gandhi, the president of Venezuela, the Mauritius prime minister, among others, he has led a number of national and international reform programs addressing issues including traffic improvement, social security and healthcare reform and internet access improvement and fitness through'CardioSalsa' and'Running Pushups', STEM+ Education.
A former champion athlete and owner of a global tennis academy, he mentored several tennis legends including Andre Agassi and Monica Seles. His global impact has been driven by a number of groundbreaking philosophies captured in acronyms such as the 3 Ws for healthy partnerships, 3Ps for successful programs, 3 performance measuring Es, 4 health reduce Ss, most notably MBS, a practical pathway to happiness, captured in his Happy Executive book, lauded by Kirkus. Appu Kuttan was born in 1941 in India, he received his bachelor's degree in Electrical Engineering from the Kerala University in 1963, moved to the United States in 1964 on a Tata scholarship to attend Washington University. He graduated from WU with a master's degree in 1966, earned a PhD in industrial engineering at the University of Wisconsin-Madison in 1968. Early in his career, Kuttan created the Management By Systems concept of setting specific goals and objectives, achieving them by deploying available resources systematically and effectively.
In the 1970s, he was invited by the Governor of Puerto Rico to improve their traffic system by applying his MBS strategies. Through implementing his groundbreaking 3 E's philosophy, he was able to improve the management of delinquent traffic officers and by reducing public drunkenness, he achieved a dramatic 20% reduction in traffic related deaths. Soon after, he worked with the Venezuelan government to improve their social security and healthcare programs. In 1980, he served as an informal adviser to future Indian Prime Minister Rajiv Gandhi, focusing on how to make India an information technology power using India's educated manpower, strategies that were implemented when Gandhi took power in 1984, he advised the Prime Minister of Mauritius on making Mauritius an IT-focused nation, has advised the U. S. administrations of Bill Clinton, George W. Bush, Barack Obama. In 1986, he purchased the Nick Bollettieri Tennis Academy in Florida and helped develop and mentor tennis world champions Andre Agassi and Monica Seles.
Founded by Appu Kuttan in 1989 with proceeds from the sale of the tennis academy, the National Education Foundation is a nonprofit organization based in the Washington, DC Metro area. NEF provides disadvantaged students, teachers and jobseekers top-quality tuition-free STEM+ education in the United States and India. Kuttan remains chairman of the board. Launched in 1993, the NEF CyberLearning provides students in disadvantaged U. S. schools with access to science, engineering, English, social studies and test prep skills. CyberLearning offers 6,000 online courses to help disadvantaged adults. NEF CyberLearning partners with the State University of New York to create STEM+ Academies, a remarkable education solution that includes personalized learning, teacher stipends, student rewards and parent training. Lehighton Area School District, PA, won NEF's 2016 STEM+ Academy of the Year, because their students advanced a grade level in math and reading in just 26 and 27 learning hours respectively. On January 7, 2017, NEF launched a $100 Million Grant initiative for schools across the U.
S. to boost STEM education. Kuttan’s book Happy Executive — A Systems Approach: Nurturing Mind and Soul is his memoir, a self-help guide for business executives. According to Kirkus, the book provides “a methodical, well-organized guide for the world’s future leaders.”In March 2003, Kuttan and Dr. Laurence Peters published a text book titled From Digital Divide to Digital Opportunity. In August 2006, Certiport named Kuttan their Global Digital Literacy Champion, an annual prize awarded for spreading computer literacy around the world, stating, "We selected Dr. Appu Kuttan unanimously for this prestigious award because of his outstanding leadership and contributions towards advancing digital literacy in many countries over many years." On October 14, 2011, University of Wisconsin-Madison College of Engineering gave Appu Kuttan a Distinguished Ac
The 2013–14 Towson Tigers men's basketball team represented Towson University during the 2013–14 NCAA Division I men's basketball season. The Tigers, led by third year head coach Pat Skerry, played their home games at the brand new SECU Arena and were members of the Colonial Athletic Association, they finished the season 13 -- 3 in CAA play to finish in second place. They advanced to the semifinals of the CAA Tournament where they lost to Mary, they were invited to the CollegeInsider.com Tournament where they defeated USC Upstate and East Tennessee State to advance to the quarterfinals where they lost to Murray State. * Jerome Hairston left the team on January 7, 2014 after being suspended
Hakea costata known as the ribbed hakea, is a shrub in the family Proteaceae native to Western Australia. A multi-stemmed small shrub producing attractive pink or white brush-like blooms rich in nectar from July to October. Hakea costata is an erect non-lignotuberous shrub growing to 0.3 to 2 metres high. The smaller branches are densely covered in long soft straight hairs. Leaves vary depending on. Near the flowers the leaves are linear and triangular in cross-section 8 to 16 mm long and 1 to 2.5 mm wide. The leaves below flowers are flat, narrowly egg-shaped to oval shaped 2 to 5 millimetres wide; the leaves upper surface have no obvious veins. The inflorescence has 8-12 scented white or pink flowers in racemes 8–16 cm long appearing in leaf axils from July to October; the perianth is pistil 6 to 9 mm long. The small fruit are attached to the stem without a stalk, more or less egg-shaped 09–1 cm long and 0.6–0.8 mm wide curved ending with a short beak. The fruit surface is smooth to warty; the black-brown seeds are more or less elliptic shaped with a wide wing down one side and a narrower wing down the other.
Hakea costata was first formally described by the botanist Carl Meissner in 1845 and published in Johann Georg Christian Lehmann's book Plantae Preissianae. The specific epithet is derived from the Latin meaning "ribbed", referring to the longitudinal ribbing of the leaves. Ribbed hakea is endemic to an area along the west coast in the Wheatbelt and Mid West regions of Western Australia from about Kalbarri in the north to Yanchep in the south growing in sandy soils over limestone or laterite
The Port of Póvoa de Varzim is a seaport built in Enseada da Póvoa Bay in the city of Póvoa de Varzim in Portugal. During the Middle Ages, it was known as Port of Varzim. Once used for trade and shipbuilding, it is used for fishing and recreation, with a marina located within its breakwaters; the port was fundamental to the establishment of Póvoa de Varzim as a municipality in 1308 and the development of the town. During the Middle Ages, its profitability attracted knights and the Church. In this small bay the local fishermen developed the Poveiro boats and Povoan knowledge of the seas and shipbuilding were substantial during the Age of Discovery. After 1000 years of recorded history and continuous use, the port of Póvoa de Varzim became a notable and prosperous fishing port in the 18th century due to its fishermen's seafaring and fishing expertise, considered the best in Portugal; the north breakwater, the main one, is known as "Paredão". It was first rebuilt in the following centuries; the most important works on the port were made during the Salazar regime in the early 20th century.
The port is protected by the north breakwater, heading south-southwest, which has a lighthouse with a red flashing light and a siren. The south breakwater heads north-northwest. Archaeological data around the port of Póvoa de Varzim date to the Roman period. A Roman fish factory could have existed in the area of Junqueira, bordering the port, where a number of artifacts were found. A factory is known, in the northern area of the city near the cove of Lagoa Beach; the historical records of the seaport dates to the 11th century, when the sheltered bay started being used by ships due to its sheltered characteristics. In the 11th century, Guterre Pelayo became the Lord of Varzim. According to the Livro Velho de Linhagens, the Ancient Book of Ancestries, he acquired the port of Varzim and several other possessions from Henry, Count of Portugal. Guterre was a decisive Reconquista captain during those years. One of the great-grandsons of Guterre Pelayo, Lourenço Fernandes da Cunha had great fortune in the town of Varzim and surrounding land.
His family ruled the area as the Honour of a knights honour. Sancho, as king of Portugal, disliked the power Lourenço got, as such the king ordered the destruction of several of his properties and took over most of the land. In the 1220 inquiries it was said that in the Royal Land of Varzim, a royal butler area, there were 20 families, who gave to the King, when he came into town, 6 dinheiros for the stay. One of the sons of Dom Lourenço was Gomes Lourenço influential knight and godfather of King Denis. Dom Gomes Lourenço, as it is deduced from his personal 1290 Inquiries, took advantage of his relationship with important people in order to get the recognition of the seaport of Varzim, located in Lower Varzim, as his honour, he tried to convince King Denis, that Afonso III, took it from him unfairly. In this way, Dom Gomes and his descendants, who are part of the honour of Varzim, went to the seaport and got the navão from the fishermen, justifying the attitude with the honor. By this, King Denis granted a Royal Charter to Varzim in 1308, ordering some local inhabitants to build a maritime settlement, he promoted farming development and the use of the seaport for the transport of production such as bread and salt, but fisheries from which the king took the best profits "the whale, the dolphin or royal belongings", that is, the most profitable catches.
One of the terms of the charter ordered the inhabitants who brought bread, salt or sardines, when unloading ferries or vessels in the port of Póvoa de Varzim, granted for each ferry or vessel, 7 soldos. These were the customs rights that substituted the navão. Pinho Leal, in the book Portugal Antigo e Moderno, stated that Castelo da Póvoa fort, was built in the 15th century, during the reign of John I of Portugal in order to protect the port. In the 16th century, the fishermen started to work in maritime activities, as pilots or seafarers in the crew of the Portuguese ships, due to their high nautical knowledge; the fishermen of the region are known to fish in Newfoundland since, at least, 1506. In 1547, a registry of ships docking or leaving the port was made by the main guard Annes Cadilhe, in which an English ship was noticeable. In the seaport documents, the construction of a notable ship is documented: the warship N. S. de Guadalupe built in Póvoa sheltered bay, with Povoan Diogo Dias de São Pedro as captain, who gained fame in the squadron that gettered in Lisbon to restore Pernambuco on March 15, 1631, that the Dutch captured in 1630.
The carrack was constructed by Povoan merchants and Captain Diogo Dias did not want to accept the government's gratifications, paid the crew with his own money, who followed him with dedication and courage. Years the carrack returned to the port, after trading in Angola, his brother, António Cardina, Póvoa de Varzim's town hall judge, was the main pilot of the Portuguese armada and gained notability in the defense and liberation of the city of Bahia captured by the Dutch. In the 17th century, there was an increase in shipbuilding activities and a significant part of the population worked as Ribeira carpenters or related activities. In the 17th century, fishing activities started to be of significant economic va
James Herman Banning was an American aviation pioneer. In 1932, James Banning, accompanied by Thomas C. Allen, became America's first black aviator to fly coast-to-coast. Dreaming from boyhood of being a pilot, Banning learned to fly from an army aviator after being turned away from flight schools due to racial discrimination, he became a demonstration pilot on the west coast, flying a biplane named "Miss Ames". James Banning and his mechanic Thomas Allen made the historic flight using a plane supplemented with surplus parts; the "Flying Hoboes," as they were affectionately known, made the 3,300 mile trip from Los Angeles to Long Island, NY in 41 hours and 27 minutes aloft. However, the trip required 21 days to complete because the pilots had to raise money for the next leg of the trip each time they stopped. Only four months after his historic flight, Banning was killed in a plane crash during an air show at Camp Kearny military base in San Diego on February 5, 1933, he was a passenger in a two-seater Travelaire biplane flown by Navy machinist mate second class Albert Burghardt, at the controls because Banning had been refused use of the airplane by an instructor at the Airtech Flying School.
After taking off and climbing four-hundred feet, the plane stalled and entered an unrecoverable tailspin in front of hundreds of horrified spectators. Banning was recovered from the wreckage and died one hour at a local hospital. A large photograph of Banning is displayed at the Disney California Adventure section of Disneyland in Anaheim, CA at the ride Soarin' Around the World, a flight motion simulator attraction. Provided underneath his photo is a plaque with a brief summary of his achievements and accomplishments as a tribute to the Wings of Fame, a hallway where guests wait during the line queue to the actual ride where many photographs and models of early plane concepts are displayed, including homages to significant individuals in aviation history, including James Banning on the right side. Emory Conrad Malick