Process of Meiosis | Experiment

Process of Meiosis | Experiment In this experiment we observed the process of meiosis by looking at different slides. Meiosis is a process in which a diploid (2n) parent cell is divided into four haploid (n) daughter cells. The daughter cells have half the number of chromosomes as the parent cell. Meiosis mainly occurs in sex cells (gametes) of humans through the process of spermatogenesis (males) or oogenesis (females). It is essential for sexual reproduction, and thus is seen in all eukaryotes that reproduce sexually. Before the cell undergoes meiosis, it first replicates its DNA. Meiosis includes 2 cycles of division- meiosis I and meiosis II. After meiosis I is completed, DNA is not replicated, which leads to the final daughter cells being haploid (n). The first step of meiosis I is prophase I. During prophase I, DNA can be exchanged between homologous chromosomes by tetrads crossing over, a process referred to as recombination. The new combination of DNA provides for genetic variation for the daughter cells. I n addition, in prophase I, the nuclear envelope disintegrates, and the two centrioles move to opposite ends of the cell. In metaphase I, homologous chromosomes are aligned at the metaphase plate (site where the cell will divide) in pairs. The side at which homologous pairs will lineup is random and further improves the chances for genetic variation. The centrioles attach kinetochore microtubules to the chromosomes, so that they can be pulled apart to the different ends as the cell divides. In anaphase I, the microtubules shorten, pulling the pairs of homologous chromosomes apart from one another. In telophase I, the chromosomes arrive at their respective ends and the cell divides to form two haploid cells. The nuclear membrane is reformed, and the microtubules disappear. The chromosomes uncoil back into chromatin. Note, that even though the first meiotic division led to two haploid cells, each chromosome still contains a pair of sister chromatids. Thus, meiosis II begins without DNA replicating beforehand. The steps in meiosis II are very similar to the ones in meiosis I. In prophase II, the nuclear envelope disintegrates, the centrioles move to the opposite end of the pole, the chromosomes condense and prepare for the second division. In metaphase II, the chromosomes again line up randomly at the plate, but this time independently, not in pairs. The spindle network is formed is also formed. In anaphase II, the sister chromatids are pulled apart and move toward the opposite ends of the pole. Lastly, in telophase II, the cells are cleaved and the nuclear envelope reappears. The chromosomes uncoil and the end result is 4 haploid daughter cells. In spermatogenesis, the 4 daughter cells are the spermatids. However, in oogenesis, even though 4 haploid daughter cells are created, 3 are polar bodies, while the last is an ootid (egg), which might be fertilized by a spermatid. During fertilization (when the spermatid and ootid join), the number of chromosomes reverts b ack to 2n (diploid). The random alignment and crossing over are very important to the process of meiosis because they provide for greater genotypic diversity. However, if the chromosomes are not able to separate, several errors can arise. Klinefelter and Turner syndromes are due to nondisjunction, during which there is an extra X chromosome present in males, or missing an X chromosome in females, respectively (Russell, 346-349). We also observed the life cycle of the insect drosophila. We will be experimenting on them in the coming weeks. This insect serves as a great experimental organism in the field of genetics due to its short, unique life cycle, and since Mendels laws of inheritance (law of segregation, law of independent assortment) are clearly visible when they mate. The law of segregation states that when any individual produces gametes, the copies of a gene separate so that each gamete receives only one copy. The law of independent assortment states that alleles of differen t genes assort independently from each other during gamete formation. The purpose of this experiment was to familiarize ourselves with the process of meiosis and the insect drosophila, as we will be working with them in future experiments. We used slides from human testis, rat testis, and chorthippus testis, to compare the process of meiosis in different eukaryotes. I predict that I will be able to see the stages of prophase, metaphase, anaphase and telophase in the slides. Hypothesis: I believe that the process of meiosis will be the same in all three eukaryotes, and I will be able to view the cells differentiating. I should be able to see the different structures of the insects and be able to distinguish male and female drosophilas based on their appearance. I believe that I will be able to witness the different stages of meiosis in the slides. Methods: Obtain the slides and the compound light microscope from the instructor. Place the first slide on the stage of the microscope (the microscope should be on the lowest power- 40x) and use the coarse adjustment knob to focus the slide. Turn to the next highest power (100x), and this time, use only the fine adjustment knob to bring the slide into focus. Turn the microscope to the 400x power, and again focus the slide. Sketch what you see on a separate sheet of paper and label the different structures. Before moving on to the oil immersion power, put a little drop of oil in the middle of the slide. Focus the image under oil immersion and sketch the results once again. After youre done sketching the slide, lower the stage and put the microscope back to the lowest power (CAUTION: be careful not to get oil on the 400x power when turning the objectives as this will ruin the lens). Repeat these steps for the rest of the slides (NOTE: for the drosophila male and female slide, the lowest power, 40x, is good enough to get a good overview). The slides we viewed were: chorthippus testis, generalized animal cell, human chromosome (metaphase state), turtle liver mitochondria, drosophila chromosome, drosophila (male and female), rat testis, and human testis. At the end of the experiment, clean all the slides that have oil on them, wipe the oil immersion lens, and return the materials to the instructor. Results: Questions: 1. What major chromosomal event occurs between leptonema and zygonema? Between leptonema and zygonema, the major chromosomal event that occurs is the pairing of the homologous chromosomes. 2. Do any of the chromosomes at zygonema appear to consist of two parallel parts? How do you account for this appearance? Yes, chromosomes at zygonema appear to consist of two parallel parts, which is probably due to the paired homologues. 3. Consult your textbook for a definition of the term chromomere. Can you detect chromomeres in any of the meiotic cells you are examining? At what substages of prophase I are chromomeres evident? Chromomeres are dark regions of chromatin condensation. Yes, you can detect chromomeres in meitotic cells; they are usually seen in zygonema of prophase I. 4. Do you observe a large, darkly staining structure in the nucleus during leptonema and zygonema? This body represents an already highly condensed (heterochromatic) X chromosome. Can you follow the fate of this chromosome through the rest of the substages of prophase I and metaphase I? Yes, it should be possible to follow the fate of this chromosome through the rest of the substages of prophase I and metaphase I. This X chromosome will not align with the rest of the chromosomes at the metaphase plate and will be near one end of the splitting cell or the other. 5. Briefly list major differences between zygonema and pachynema. At zygonema, the chromosomes are much less condensed than those at pachynema. Crossing over occurs at pachynema. The number of chromosomes can be determined at pachynema, but not at zygonema. 6. Locate cells in diplonema. Can you observe a) the two homologous chromosomes in a pair? b) individual chromatids in a chromosome? c) chiasmata? a) Yes, the homologous chromosomes in pairs are visible. b) Yes, the chromatids are also visible, since the chromosomes at this stage are much coiled. c) Yes, the chiasmata is visible, it is the point where the pair of homologous chromosomes exchange genetic material. 7. Because of the degree of condensation of the chromosomes, diakinesis is an ideal stage at which to determine the chromosome number. Count the chromosomes in a grasshopper cell at diakinesis. Record the number here. Does this represent the diploid number? Justify your answer. Note that sex in grasshoppers is determined by an XO mechanism in which the female is XX, but the male has a single X chromosome. Therefore, the X chromosome that you observe in diakinesis is not a tetrad. What is the significance of this information for determining chromosome number in grasshopper males versus females? Since grasshopper males are missing an X chromosome, to find their diploid number of chromosomes, one would have to count the haploid number (n), double it (2n), but then subtract 1, since it is missing an X chromosome. In females, the subtraction will not be necessary; they will always have double their haploid number of chromosomes (example- if haploid number equals 14 chromosomes, male diploid number will equal (2n-1 = 28-1) 27 chromosomes, while the females will have 28 chromosomes in a diploid cell). 8. Observe several cells in metaphase I. Do you notice a chromosome in an unusual position with respect to the other chromosomes in the cell? What chromosome might this be? Yes, this chromosome could be the X or Y chromosome. 9. Can you find cells in other stages of meiosis or sperm differentiation? If so, briefly describe their appearance and state what stages you think they might be. Yes, it is possible to find other stages of meiosis. In metaphase, the chromosomes are lined up at the metaphase plate. In anaphase, the chromosomes are being pulled apart, and in telophase the cells should be separating via cytokinesis. Conclusion: The process of meiosis is very complicated, but is necessary for sexual reproduction. There are five substages of prophase I in meiosis. Prophase I is the most important stage in meiosis, since this is the stage where crossing over occurs between homologous pairs of chromosomes, which is essential for genetic variation. The first substage is leptonema where chromosomes begin to condense into long strands and begin to look for their homologous pair. In the second substage, zygonema, the chromosomes have found their pairs. The third substage, pachynema, is where crossing over occurs. In addition, the chromosomes are condensed enough so that one can count the number of chromosomes. In the fourth substage, diplonema, portions of the chromosome begin to separate, and the chiasmata (the site where crossing over takes place) is made visible. The last stage, diakenisis, is where the nucleoli disappears, the nuclear membrane disintegrates, and the four tetrads of a pair of homologous chromoso mes are clearly visible (the chromosomes are fully condensed) (Meiosis Prophase I). When looking at the drosophilas, males were easily distinguishable from females. Males were smaller in size compared to the females. The end of the male was more rounded, while the female was pointier. Females had more of a striped pattern on their ends, while males have black as the dominant color. Lastly, males have a sex comb at the joint of each front leg (males also have a penis) (Hammersmith Mertens, 5). In the generalized animal cell, I was able to identify the nucleus and the nuclear envelope. In the human chromosome slide of metaphase, the chromosomes were lined up, which means they were about to be separated. In the human, rat and chorthippus testis, I had a difficult time identifying the different cell types, or cells in different phases of meiosis. Meiosis is an essential process, and if an error occurs, the consequences could be lethal.

A Biography on Martin Luther King Jr. :: essays research papers

Martin Luther King Jr. (1929-1968) was born in Atlanta, Georgia, where his father was pastor of the Ebenezer Baptist Church. He attended public schools (skipping the ninth and twelfth grades) and entered Morehouse College in Atlanta. He was ordained as a Baptist minister just before his graduation in 1948. He then enrolled in Crozer Theological Seminary in Pennsylvania and after earning a divinity degree there, attended graduate school at Boston University, where he earned a Ph.D. in theology in 1955. At Boston University, he met Coretta Scott; they were married in 1953. King's rise to national and international prominence began in Montgomery, Alabama, in 1955. In that year, Rosa Parks, an African American woman, was arrested for refusing to obey a city ordinance that required African Americans to sit or stand at the back of municipal buses. The African American citizens of the city (one of the most thoroughly segregated in the South) organized a bus boycott in protest and asked King to serve as their leader. Thousands boycotted the buses for more than a year, and despite segregationist violence against them, King grounded their protests on his deeply held belief in nonviolence. In 1956, the U.S. Supreme Court ordered Montgomery to provide integrated seating on public buses. In the following year, King and other African American ministers founded the Southern Christian Leadership Conference (SCLC) to carry forward the nonviolent struggle against segregation and legal discrimination. As protests grew, so did the unhappiness of King and his associates with the unwillingness of the president and Congress to support civil rights. The SCLC, therefore, organized massive demonstrations in Montgomery (King wrote "Letter from Birmingham Jail" during these demonstrations). With the civil rights movement now in the headlines almost every day, President Kennedy proposed to Congress a far-reaching civil rights bill. On August 28, 1963, over 200,000 blacks and whites gathered at the Lincoln Memorial in Washington, D.C., where King delivered his now famous speech, "I Have a Dream." In the following year, Congress passed the Civil Rights Act of 1964, prohibiting racial discrimination in public places and calling for equal opportunity in education and employment. In that year, King received the Nobel Peace Prize. In 1965, King and others organized a march to protest the blatant denial of African Americans' voting rights in Selma, Alabama, where the march began. Before the protesters were able to reach Birmingham, the state capital, they were attacked by police with tear gas and clubs.

Administrative Issues and closeout, Sponsor interactions, IRB communication, Document retention, Close-out

Drug research and development are an essential part of the medical and pharmaceutical company today and therefore each step has to be taken cautiously to keep the process flawless and thereby maintain the efficiency of the system.The system is rendered useless if there are fingers being pointed at the preciseness and the authenticity of the outcome of the research. Issues may crop up related to the research due to a difference in the interest of the scientists and the financial interests of researchers in the study, thereby making it the responsibility of the staff or the pollster to make others aware of the underlying rift in the interests of the two.The function of the food and drug administration (FDA) is to gauge the researches that are requirements of the law needed for the development of new medicines and other similar products and to apply for re-categorizing medical instruments and gadgets, together with upgrading the image of these products.Moreover it minutely scrutinizes e ach and every detail of the data put forth so as to be sure that the research had been done with the required steps so that the study is neutral.The other duty of the FDA is to remain fully aware of the benefit of the sponsors and the clinical investigators, and   the reason why the study is being carried out, and therefore analyze if both are appropriate to each other or not. It even keeps a check by visiting the sites to be sure about the authenticity of the results. (Source: Good Clinical Practice Regulations)The secretary of the US department of the Health and Human services, Tommy G Thompson has stated that the best way to preserve the efficiency of the research is by maintaining the ethics in the study, and the preeminent way to do this is by keeping nothing hidden from all the elements involved in the research, Therefore, shielding all the subjects in the study.There is a report by the name of â€Å"Financial Relationships and Interests in Research Involving Human Subjects : Guidance for Human Subject Protection† which is followed by the HHS and FDA in all the researches that they undertake, aimed at providing a written guidance about the rights of all the human subjects that are a part of the study. (Source: HHS Provides Guidance on Financial Relationships and Interests in Research Involving Human Subjects)The other issue that comes forth is the imbursement to the people taking part in the study. It has been known that the subjects have been paid, but on what grounds, that still is questionable as any written proof on this subject matter has yet not been found.Even the federal and the experts of the field (being researched) do not see eye to eye on this matter. This is where the Institutional Review Boards step in.These agencies are aimed at ensuring that no harm what so ever is caused to the subjects of the research and that they were not brain washed or coerced to be a part of the study and that it was solely their decision to participate. (S ource: National practices regarding payment to research subjects for  participating in pediatric research)There are however certain rules that have to be abided by when it comes to paying the subjects. Firstly that the payments should be made in bits as the study progresses, however if any of the subjects back off before the completion of the research   in that case the payment should be made at the time that had been promised to them had they not backed out.Moreover a check should be made that incase if an additional benefit is to be given to the subject, then it should not be a handsome amount so that it holds the subject back to remain in the research out of greed who would have otherwise not been a part of any longer therefore every monetary dealing should also be documented and written in the approval. (Source: National practices regarding payment to research subjects for  participating in pediatric research)ReferencesUS Food and Drug Adinistration (2006).   Good Clinic al Practice Regulations.   Read the sections in part 312 related to financial disclosure (part 54).   Retrieved on  July 24, 2008  from  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚   http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?CFRPart=54 Department of Health and Human Services (2004).   HHS Provides Guidance on Financial Relationships and Interests in Research Involving Human Subjects.   Retrieved on July 24, 2008 from http://www.hhs.gov/news/press/2004pres/20040512.html. Weise, K. L., Smith, M. L., Maschke, K. J. and Copeland, H. L. (2002). National practices regarding payment to research subjects for  participating in pediatric research.   Pediatrics 110 (3), 577.   Retrieved on May 21, 2008 from  http://pediatrics.aappublications.org/cgi/content/full/110/3/577?ck=nck.

The Most Beautiful And Greatest Musical Works Of The 20th...

On November 2, I was delighted to attend â€Å"Solemn Mass for the Dead on the Feast of All Souls† at St. James Cathedral. Now I still feel highly honored to hear Maurice Duruflà ©Ã¢â‚¬â„¢s Requiem—one of the most beautiful and greatest musical works of the 20th century. As an international student from China and have no religion belief, it’s totally brand new and unusual experience for me to have this special chance to open my eyes widely to see the magnificent church. This opportunity is of great benefit to me to learn Catholic Church and acquaintance with religious faith. What I saw at St. James is the first person lifted the cross with corpus hang on it. Following on are the younger disciples held lighted candles. Then the elder disciples held book†¦show more content†¦First is the Introductory Rites. Secondly is the Liturgy of the word .Thirdly, the Liturgy of Eucharist .Finally , the concluding Rites. One of them is Sanctus. â€Å"Holy, holy, holy Lord, God of hosts. Heaven and earth are full of your glory. Hosanna in the highest. Blessed is he who comes in the name of the Lord. Hosanna is the highest.† We bless God as the one who has power and mercy. Another one is Introit â€Å"Eternal rest grant unto them, O Lord. And let perpetual light shine upon them. To you a hymn of praise id due, O Lord, in Zion. To you a vow must be fulfilled in Jerusalem. Hear my prayer! To you all flesh must come.† God let everlasting light shine upon us grant us eternal rest. The famous Lord’s prayer : â€Å"Our Father, who art in heaven, hallowed be thy name. The kingdom come. They will be done, on earth as it is in heaven. Give us this day our daily bread and forgive us our trespasses, as we forgive those who trespass against us. And lead us not into temptation, but deliver us from evil.† We did that before every theology class, my understanding is we should restraint temptation in our life, keep evil away from us. Prayer over the offering: Receive ,Lord you’re your kindness, the sacrificial offering we make for all your servants who sleep in Christ , that ,set free from the bonds of death by this singular sacrifice, they may merit eternal life .Through Christ and Lord.† Even for me who have no religion, I believe if you did good things, God will reward you