A Genetics Definition of Homologous Chromosomes

A Genetics Definition of Homologous Chromosomes Homologous chromosomes are chromosome pairs (one from each parent) that are similar in length, gene position, and centromere location. The position of the genes on each homologous chromosome is the same. However, the genes may contain different alleles. Chromosomes are important molecules, as they contain DNA and the genetic instructions for the direction of all cell activity. They also carry genes that determine individual traits. Homologous Chromosomes Example A human karyotype shows the complete set of human chromosomes. Human cells contain 23 pairs of chromosomes, for a total of 46. Each chromosome pair represents a set of homologous chromosomes. One chromosome in each pair is donated from the mother and the other from the father during sexual reproduction. In a karyotype, there are 22 pairs of autosomes (non-sex chromosomes) and one pair of sex chromosomes. In males, the X and Y sex chromosomes are homologs. In females, both X chromosomes are homologs. Mitosis The purpose of mitosis (nuclear division) and cell division is to replicate cells for repair and growth. Before mitosis begins, chromosomes must be replicated to ensure that each cell retains the correct number of chromosomes after cell division. Homologous chromosomes replicate forming sister chromatids (identical copies of a replicated chromosome that are attached). After replication, the single-stranded DNA becomes double-stranded and has the familiar X shape. As the cell progresses through the stages of mitosis, sister chromatids are eventually separated by spindle fibers and divided between two daughter cells. Each separated chromatid is considered a full single-stranded chromosome. Interphase: Homologous chromosomes replicate forming sister chromatidsProphase: Sister chromatids move toward the center of the cellMetaphase: Sister chromatids align along the metaphase plate at the cells centerAnaphase: Sister chromatids are separated and pulled toward opposite cell polesTelophase: Chromosomes are separated into distinct nuclei After the cytoplasm is divided during cytokinesis, two new daughter cells are formed with the same number of chromosomes in each cell. Mitosis preserves the homologous chromosome number. Meiosis Meiosis is the mechanism for gamete formation and involves a two-stage division process. Prior to meiosis, homologous chromosomes replicate forming sister chromatids. In prophase I, sister chromatids pair up forming what is called a tetrad. While in close proximity, homologous chromosomes sometimes exchange sections of DNA. This is known as genetic recombination. Homologous chromosomes separate during the first meiotic division and sister chromatids separate during the second division. At the end of meiosis, four daughter cells are produced. Each cell is haploid and contains half the number of chromosomes as the original cell. Each chromosome has the appropriate number of genes, however, the alleles for the genes are different. The swapping of genes during homologous chromosome recombination produces genetic variation in organisms that reproduce sexually. Upon fertilization, haploid gametes become a diploid organism. Nondisjunction and Mutations Occasionally, problems arise in cell division that cause cells to divide improperly. Failure of chromosomes to separate correctly in mitosis or meiosis is called nondisjunction. Should nondisjunction occur in the first meiotic division, homologous chromosomes remain paired. This results in two daughter cells with an extra set of chromosomes and two daughter cells with no chromosomes. Nondisjunction may also occur in meiosis II when sister chromatids fail to separate prior to cell division. Fertilization of these gametes produces individuals with either too many or not enough chromosomes. Nondisjunction is often fatal or may produce chromosomal anomalies resulting in birth defects. In trisomy nondisjunction, cells contain an extra chromosome. In humans, this means that there are 47 total chromosomes instead of 46. Trisomy is seen in Down syndrome where chromosome 21 has an additional or partial chromosome. Nondisjunction may also produce abnormalities in sex chromosomes. Monosomy is a type of nondisjunction in which only one chromosome is present. Females with Turner syndrome have only one X sex chromosome. Males with XYY syndrome have an extra Y sex chromosome. Nondisjunction in sex chromosomes typically has less severe consequences than nondisjunction in autosomal chromosomes (non-sex chromosomes). Chromosome mutations can impact both homologous chromosomes and non-homologous chromosomes. A translocation mutation is a type of mutation in which a piece of one chromosome breaks off and is joined to another chromosome. This type of mutation occurs more often between non-homologous chromosomes and can be reciprocal (gene exchange between two chromosomes) or non-reciprocal (only one chromosome receives a new gene segment).

Winter Holiday Activities for Grades 5-12

Winter Holiday Activities for Grades 5-12 How can teachers, especially in public schools, use the December holidays to their advantage? One way is to celebrate customs and holidays from around the world with students using a variety of activities.   Here are some ideas for meaningful and educational activities for students ahead of their winter break, making use of holiday themes celebrated near the end of the year. Christmas According to Christian belief, Jesus was the son of God born to a virgin in a manger. Countries around the world celebrate this holiday in various ways. Each of these customs as described below are ripe for investigation by students. Christmas Around the World Costa Rica: The weather is warm at Christmastime. Trees are popular. Tamales and Empanadas are traditionally eaten.England: Santa Claus is known here by the name Father Christmas. Christmas trees are decorated and stockings are hung. A drink called  Wassail  is served. Boxing Day is celebrated on December 26th which is also the feast day of St. Stephen. On this day, it is traditional to give alms to the poor and less fortunate.France: A popular dessert called the buche de noel or Christmas Log is consumed on Christmas. Often, a feast occurs after Midnight Mass on Christmas eve called the rveillon. Gifts are given by pere noel which means Father Christmas. He travels with a man called Pre Fouettard who tells pere noel how the children behaved during the previous year. In some parts of France, gifts are given on both December 6th (St. Nicholas feast day) and on Christmas. Adults give gifts on New Years.Italy: Christmas is celebrated with a large feast after a 24-hour fast before Ch ristmas. Children usually do not receive their presents until January 6th, the day of the Epiphany. These gifts are brought by Le Befana, a woman who flies around on a broom. Kenya: Lots of food is prepared, especially goat. They serve a flatbread called chapatis. Groups often go singing house to house and receive gifts of some kind from the occupants. On Christmas, these singers give any gifts to their church.United States: Christmas trees, real or artificial, are put up in homes early in December. They are usually decorated with multi-color lights and various ornaments. Stockings are hung, often on the fireplace mantel. On Christmas eve, children set out cookies or other goodies for Santa Claus. On Christmas morning, children rush to the tree to see the gifts there and in their stockings. Ideas for Christmas-Themed Projects Investigate the legend of Santa Claus.Investigate different aspects of the Christmas celebration including the tree, the decorations, the stockings, the carols and more.Perform Christmas songs in either English or other languages.Investigate traditional foods for each culture and create them for the rest of the class to sample.Present skits representing each cultures customs.In many countries, Christmas celebrations are becoming more like those  in America. Debate whether the loss of the countries traditional celebrations is good or bad.Read O.  Henrys The Gift of the Magi and discuss its meaning.Students could write in their journals about numerous topics including:Worst Christmas experienceBest Christmas experienceFamily traditionsWhat Santa Claus means to themIs Christmas too commercial? Winter Solstice The Winter Solstice, the shortest day of the year when the sun is closest to the earth, occurs on the 21st of December. In ancient times, this was celebrated in various ways by Pagan religions. Groups ranging from Germanic tribes to the Roman populace celebrated mid-winter festivals during our month of December. Of course today, three major holidays are celebrated in America during the month of December: Chanukah, Christmas, and Kwanzaa. We can create our own festival allowing us to experience how other cultures celebrate these holidays. Method of Presentation Many methods exist for creating this festival atmosphere. These range from simple classroom stations presented by groups of students about each culture to schoolwide activities that take place in a large auditorium/cafeteria and allow for more than just static presentations. Students can sing, cook, give presentations, perform skits, and more. This is a great opportunity to have students work  cooperatively  in groups to gather information about holidays and customs. Chanukah This holiday, also known as the Festival of Lights, is celebrated over eight days beginning on the 25th day of the Jewish month of Kislev.  In 165 BCE, the Jews led by the Maccabees defeated the Greeks in war. When they arrived to rededicate the Temple in Jerusalem they found only one small flask of oil to light the  Menorah. Miraculously, this oil lasted for eight days. today, Chanukah is traditionally observed in the following ways: Every night for the eight days of the festival of Chanukah, lights are lit on a  Menorah  to commemorate the miracle at the Temple over 2000 years ago.While work is not prohibited, people generally refrain from work while the Chanukah lights are lit.The  dreidel  is used by families to play a game. The history behind this game played during Chanukah is believed to relate back to a ban on work while the Chanukah candles are lit.Those celebrating the holiday eat traditionally  Ã¢â‚¬â€¹oily foods to commemorate the miracle of the oil.Children are given presents and money during the holiday. Many families give out presents each day of the holiday. This relates to rewarding children for Torah study.Many different traditions exist around the world for this celebration. Ideas for Chanukah Presentations In addition to adapting the ideas listed above for Christmas celebrations, here are some ideas for Chanukah-themed projects. Students can: Research the background to ChanukahPlay  dreidel  gamesPerform Chanukah songs Kwanzaa Kwanzaa, meaning the first fruits, was developed in 1966 by Dr. Maulana Karenga. It gives African-Americans a holiday dedicated to preserving, revitalizing, and promoting African-American culture. It focuses on seven principles with emphasis on the unity of the black family: Unity, self-determination, collective work and responsibility, cooperative economics, purpose, creativity, and faith. This holiday is celebrated from December 26th through January 1st. On each of the seven days of Kwanzaa, greetings are exchanged in Swahili. The question, Habari gani? is asked and each day the principle for that day is the answer. For example, the first days answer would be Umoja or unity.Gifts are given to children and include a book and a  heritage symbol.  The colors of Kwanzaa are red, black, and green.Seven candles in a Kinara are lit, one for each day of the holiday. One is black and represents the people. This candle is lit first. Three red candles are placed to the left of the black candle representing the struggle for African Americans. Three green candles are placed to the right of the black candle representing the future and hope. These candles are lit from left to right, one for each day. Ideas for Kwanzaa  Presentations Have students discuss each of the seven principles and why they are important.Students can discuss the necessity of holidays in making up group identities.Speakers can come in to discuss Kwanzaa and how it is celebrated.Students can create a  traditional Kwanzaa celebration in the classroom.The Civil Rights movement can be discussed in the context of the Kwanzaa celebration.

Risk Management Essay Example | Topics and Well Written Essays - 1500 words

Risk Management - Essay Example To do this, the airline embarks on several risk management processes. It is not surprising therefore that for all but the second year of operation Emirates Airlines have recorded profits and growth that always span above 20% (CNN Money, 2005). The airline has recorded a profit every year, except the second, and growth has never fallen below 20% a year. In its first 11 years, it doubled in size every 3.5 years, and has every four years since Current Risk Management Process In the view of Tatum (2011), Risk management is a logical process or approach that seeks to eliminate or at least minimize the level of risk associated with a business operation. Kolakowski (2011) posits that â€Å"risk management is concerned with identifying and measuring the risks faced by the firm.† This makes risk management more of a preventive venture than a curative one. In light of this, the Risk Management Magazine (2011) argues that, most airlines have their risk management undertaken by the intern al audit department. Risk management undertaken by companies varies in scope. Some of the commonest identified scopes of risk management include financial risk and field risk. With particular emphasis on the Emirates Airlines and other aviation services, special emphasis are laid on risk associated with staff and customer safety of customers and staff when talking about risk management. Commenting on a typically workable risk management model for airlines, the Risk Management Magazine (2006) outlines nine areas that airlines could look out for in their risk management exercises. These nines models are â€Å"station size, last audit date, last management change, prior audit report rating, compliance with submitting inventory reports, promptness of remitting funds, promptness of submitting sales reports, magnitude of unreported sales (passengers flown for which the ticket sale was not located), and magnitude of discrepancies with local disbursements† (Goepfert, 2006). Still wri ting on management process for airlines, the International Air Transport Association (2010) outlines areas that airlines may consider in their risk management efforts. According to the association, â€Å"Crew fatigue has typically been controlled by a simple set of prescriptive rules concerning flight time limitations (FTL) and flight duty limitations (FDL).† These model, when carefully followed by airlines guarantees financial returns as well as employee and customer safety. Such safety assured among customer also goes a long way to promote a continued business relations with the airline and invariable ensures profitability for the company. Risk Management Problems Like in every other human endeavor, undertaking a useful measure towards the growth of a company does not come easily. In an attempt to ensuring risk management, there certain challenges that the management of Emirates Airline encounters. First and foremost, there is the problem of defining potential risk. Brodzin ski (2006) notes that the definition to a risk too general. This is to say that in an organization such as an airline where there are certainly many managers in charge of the risk management business of the organization, coming to a consensus about what to include in the risk management plan of the organization always becomes the first and most challenging task. This is because what may seem to be a potential risk to manager ‘A’ may not seem a risk to manager ‘B’. It should however take the identification of a problem before any further action on

Cracking time for different protocols Essay Example | Topics and Well Written Essays - 500 words

Cracking time for different protocols - Essay Example 2). This is because these protocols do not need the usage of encoded that could make sure the privacy or discretion of email messages. Another example of how different protocol designs affect the time needed to hack is intrusion hacking. Intruders use a range of attacking mechanisms to acquire access to networks. These mechanisms consists of password-cracking mechanisms, protocol cracking, and manipulation instruments (Miltchev et al., n.d., p. 7). Detection mechanisms used by intruders help identify alterations and alternatives that occur inside networks faster in TCP/IP than POP3 or SMTP protocols. An IT team called Nohl attempted to crack the OTA protocol in 2011 and realized its design is far more secure than any products by Microsoft or Linux. Hacking the OTA protocol took the team longer to get through by sending commands to a number of SIM cards than cards with other types of security protocols such as Java (Olson, 2013). Protocol performance affects cracking time by decreasing the number of surged weak points in the respective network. Protocols with significantly better performances have environments with few weak points. In such settings, a well performing protocol dos not timeout frequently (Miltchev et al., n.d., p. 7). For example, a study conducted on protocol HACK found out that it was better than SACK because of SACK’s continuous timeouts. On the other hand, HACK was able to maintain data stream to some degree. This performance was in fact six times better in terms of output than SACK in the existence of surge errors (Balan et al., 2002, p. 359). Another case of the cracking time of protocols depending on the frequency of weak points is 2013’s powerful supercomputer NUDT Tianhe-2Â  ability to crack a 128-bit AES code. Researchers estimated that the supercomputer would take over 333 million years to crack this key, which is

Applying Thermal Expansion Essay Example for Free

Applying Thermal Expansion Essay Complete the following problems and exercises using complete sentences and showing all work where appropriate. 1. The temperature of the Suns interior is about 107 degrees. Does it matter whether this is degrees Celsius or kelvins? Defend your answer. No, it DOESNt matter whether this is in degrees Celsius or kelvins, since the DIFFERENCE between these scales is ONLY ~ 273 of either measure, and that is ABSOLUTELY NEGLIGIBLE w.r.t. the magnitude of the number 10^7. However, what is more important, perhaps, is that your value of 10^7 is itself a rather loose characterization. Modern  solar evolutionary models suggest rather that the Suns T_c is ~ 1.5 x 10^7 (degrees Celsius or kelvins) instead of merely ~ 10^7. (Our understanding of solar physics is certainly such that an error of a factor of ~ 1.5 in its central temperature would be considered way out of all reasonable possibility!) Of course the numerical factor in front of 10^7 would matter even more if one were using the (non-scientific) Fahrenheit scale. Once again, however (unlike National Geographic magazine, which should hang its head in shame over some of its conversions), one would NOT say that the Suns central temperature was about 2.7 x 10^7 and 32 degrees Fahrenheit! 2. What happens to the gas pressure within a sealed gallon can when it is heated? Cooled? Why? The gases in general obey the gas laws. As per the law the pressure,volume and temperature of the gas is related as: P1V/T1 =P2V2/T2; WhereP1 is pressure at stage 1, V1 is volume at stage 1 and T1 is temperature (Kelvin) for stage 1,and P2,V2 and T2 are the pressure,volume and temperature for stage 2. Now, if a gas contained in a sealed gallon is heatedor cooled the volume of the gas is constant but pressure and temperature will adjust u=in such a way that the : P1/T1 =P2/T2 If T2 is more than T1,then( heating the gas ) P2= P1*T2/T1 as T2 T1 so P2 will bve more than P1,hence, the pressure will increase. If T2

Women in Voltaire’s Candide Essay -- Exploitation of women in Candide

In Candide Voltaire discusses the exploitation of the female race in the eighteenth century through the women in the novel. Cunegonde, Paquette, and the Old Woman suffer through rape and sexual exploitation regardless of wealth or political connections. These characters possess very little complexity or importance in Candide. With his characterization of Cunegonde, Paquette, and the Old Woman Voltaire satirizes gender roles and highlights the impotence of women in the 1800s. Cunegonde is the daughter of a wealthy German lord. She is described as â€Å"extremely beautiful† (Voltaire. 5) and is repeatedly referred to as â€Å"the fair Cunegonde.† (39). She is the typical damsel-in-distress: a woman who is completely reliant on male protection and often fainting at the sight of anything the least bit distressing. She is a vapid beauty and completely obsequious to whomever she happens to belong to at the time. However, Voltaire does not blame her foolish naivetà © on her femininity. Candide himself is terribly innocent and is unable to make decisions without the advice of a third party. In a way, Cunegonde accepts her situation in life better than Candide does. She knows that as a woman in the eighteenth century she has few options if she wishes to survive and she is not above using her beauty to her advantage. She never questions or philosophizes like many of the male characters. Her acceptance of the sexual slavery she finds herself in beli es an understanding of the limited options women had at the time. Women in the 1800s had very few choices for advancement in life. They could either marry well or they could become the mistress of a powerful man or both. Cunegonde becomes the mistress of the Grand Inquisitor, a Bulgar captain, and the... ...ir first encounter and believes that she had no choice but to accept the governor’s offer. She states, â€Å"An honorable woman may be raped once, but it only makes her virtue stronger.† (24) For her part she does love Candide but it is a shallow love, more akin to lust. She wants to be faithful to Candide, but only if it will support the lifestyle that she is accustomed to. The women of Voltaire’s Candide emphasize the exploitation of females in the 1800s. Cunegonde, Paquette, and the Old Woman are raped, forced into prostitution, and sexually exploited. Women are valued for their beauty and can only succeed if they have pretty face to recommend them. Women in the nineteenth century exist for the pleasure of men and are subjugated to these men. Works Cited Voltaire. Candide Or, Optimism. Trans. Peter Constantine. Modern Library ed. New York: Random House, 2005

How Does Steinbeck Present Disadvantaged Characters to Us Essay

Steinbeck presents disadvantaged characters to us using a number of techniques. The author does this to encourage us to sympathise and begin to understand the characters, in order to show the problems with prejudice and the various types of it which were endemic in American society in this time. Lennie is firstly presented to us through the author’s use of animal imagery in the description, and the readers first impression of Lennie is how animal like he is when phrases like ‘snorting†¦like a horse’ are used. The author does this to show that Lennie is gentle, like an animal and can be tamed like domestic animals are. It also shows Lennie will only attack on instinct and become violent when he feels threatened or under attack. This is shown when he says ‘I didn’t want no trouble’ showing that he didn’t mean to do any harm and just doesn’t realise his own strength. The author also presents Lennie in this way because animals are innocent and do not have the capacity to act morally or know good from bad. This shows Lennie’s behaviour, when he acts violently, is a result of society as society taunts him until he behaves in this way. Lennie is also presented to the readers as a vulnerable character, through the author’s description of Lennie’s actions, especially after his attack from Curley when he ‘bleated with terror’ and ‘crouched cowering’. This action emphasises his dependence on George as he couldn’t defend himself without George telling him to. His dependence on George is also made totally clear when he says ‘me an’ him goes ever’ place together’ When Lennie panics he starts to loose control and the author presents this to the readers through the structure of the text and Lennie’s dialogue. Lennie’s sentences become short and staccato like when he says phrases such as ‘please don’t’ and ‘now don’t you do that’ showing his evident panic. The readers can also tell that Lennie looses control because the author uses language such as ‘(lennie’s) face was contorted’. The author does this to show Lennie doesn’t mean to kill or hurt and does it out of panic and instinct. This is shown by Lennie himself when he says ‘I done a real bad thing†¦ George’ll be mad’ which shows Lennie realises he can’t control himself and that he has no moral judgement. It also shows Lennie thinks things are ‘good’ or ‘bad’ to him depending on what George will think of him. The author presents Lennie to us, as a disadvantaged character, in the way he has a child’s mind in a mans body. This not only enables us to see the way in which society treats people such as Lennie but it gives us an insight into the feelings of black people as lennie, being socially unaware and childlike, does not realise the social boundries of white people and goes to talk to crooks.