A Genetics Definition of Homologous Chromosomes

A pair of homologous chromosomes contains chromosomes of similar length, gene position, and centromere location. Chromosomes are important molecules because they contain DNA and genetic instructions for the direction of all cell activity. They also carry genes that determine individual traits that can be inherited through reproduction. Human Karyotype A human karyotype shows the complete set of human chromosomes. Each human cells contain 23 pairs of chromosomes or 46 total. Every chromosome pair represents a set of homologous chromosomes. During sexual reproduction, one chromosome in each homologous pair is donated from the mother and the other from the father. In a karyotype, there are 22 pairs of autosomes or non-sex chromosomes and one pair of sex chromosomes. The sex chromosomes in both males (X and Y) and females (X and X) are homologs. Cellular Reproduction There are two ways that a cell can divide and reproduce and these are mitosis and meiosis. Mitosis exactly copies a cell and meiosis creates unique cells. Both of these methods of cellular reproduction are necessary for sustaining human life. Mitosis allows a zygote to replicate until a human is formed and meiosis produces the gametes that make fertilization, and therefore zygotes, possible in the first place. Mitosis Cellular division by mitosis replicates cells for repair and growth. Before mitosis begins, chromosomes are copied so that each cell produced retains the original number of chromosomes after division (this number is doubled and then halved). Homologous chromosomes replicate by forming identical copies of chromosomes called sister chromatids. After replication, single-stranded DNA becomes double-stranded and resembles the familiar X shape. As a cell further progresses through mitosis, sister chromatids are eventually separated by spindle fibers and distributed between two daughter cells. Each separated chromatid is considered a full single-stranded chromosome. The stages of mitosis are listed and explained in more detail below. Interphase: Homologous chromosomes replicate to form sister chromatids.Prophase: Sister chromatids migrate toward the center of a cell.Metaphase: Sister chromatids align with the metaphase plate at a cells center.Anaphase: Sister chromatids are separated and pulled toward opposite cell poles.Telophase: Chromosomes are separated into distinct nuclei. After the cytoplasm is divided during cytokinesis, the final stage of mitosis, two daughter cells are formed with the same number of chromosomes in each cell. Mitosis preserves the homologous chromosome number. Meiosis Meiosis is the mechanism of gamete formation that involves a two-stage division process. Prior to meiosis, homologous chromosomes replicate to form sister chromatids. In prophase I, the first stage of meiosis, sister chromatids pair up to form a tetrad. While in close proximity, homologous chromosomes exchange sections of DNA randomly in a process called crossing over. Homologous chromosomes separate during the first meiotic division and the resulting sister chromatids separate during the second division. At the end of meiosis, four distinct daughter cells are produced. Each of these is haploid and contains only half of the chromosomes of the original cell. The resulting chromosomes have the correct number of genes but different gene alleles. Meiosis guarantees genetic variation through genetic recombination via prophase crossover and random gamete fusion into diploid zygotes during fertilization. Nondisjunction and Mutations Problems occasionally arise in cell division that lead to improper cell division. These usually significantly affect the outcome of sexual reproduction whether the issues are present in gametes themselves or the cells that produce them. Nondisjunction Failure of chromosomes to separate during mitosis or meiosis is called nondisjunction. When nondisjunction occurs 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 at all. 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 otherwise results in birth defects. In trisomy nondisjunction, each cell contains an extra chromosome (for a total of 47 instead of 46). Trisomy is seen in Down syndrome where chromosome 21 has an additional whole or partial chromosome. Monosomy is a type of nondisjunction in which only one chromosome is present Sex Chromosomes Sex chromosomes can also suffer from nondisjunction. Turner syndrome is a form of monosomy that causes females to have only one X chromosome. Males with XYY syndrome have an extra Y sex chromosome in another example of trisomy. Nondisjunction in sex chromosomes typically has less severe consequences than nondisjunction in autosomal chromosomes, but still impacts the quality of life for an individual. Chromosome Mutations Chromosome mutations can affect both homologous 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. Translocation mutation between non-homologous chromosomes is not to be confused with crossover between homologous chromosomes or regions of chromosomes. Deletion, the loss of genetic material, and duplication, the over-copying of genetic material, are other common chromosome mutations.

Bullying At The Nursing Profession - 845 Words

Bullying in the Nursing Profession Carli Jessop Flathead Valley Community College Bullying is a term that many associate with children and while this has been recognized as a serious issue in schools across the country, such conduct unfortunately does not stop there. It has been said that nurses eat their young and while this may sound particularly extreme, bullying as well as lateral and vertical violence in the nursing profession has been an ongoing and increasingly prevalent issue in recent years. Nurses are commonly placed in leadership roles, and while one would think this would offer the opportunity to recognize and prevent this type of behavior in the workplace, the potential for abusing this power is high and the opposite repeatedly occurs. The impact of bullying and lateral and vertical violence can be severe and extremely detrimental for not only the individual on the receiving end, but the entire nursing staff as well as the patients in their care. The prevalence of bullying in the nursing profession is high according to a survey done by The Joint Commission which states more than 50% of nurses have experienced some form of bullying at work while more than 90% have reported witnessing this type of behavior. The survey also found that 75% of the nurses believed it negatively affected patient care (Felblinger, 2008). In another study, it was found that out of 303 nurses, 65% reported being bullied or had witnessed incidents of bullying (Egues Show MoreRelatedWorkplace Bullying And Its Impact On The Nursing Profession1421 Words   |  6 PagesWorkplace bullying is a growing problem in the American workplace and the Nursing Profession no exception. Addressing workplace bullying and its impact on the nursing profession is paramount to upholding patient safety and decreasing nursing attrition rates. Defining the problem is the first step in addressing it. 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Against School A Corrupted System Free Essays

The educational systems purpose is to prepare people with the necessary skills and knowledge so that they can excel and function properly in today’s society. John T. Gatto challenges that idea and begs the question is 12 compulsory years of standard schooling consisting of six classes a day, five days a week, nine months a year needed? Gatto refers to George Washington, Benjamin Franklin, Thomas Jefferson, Abraham Lincoln as they were not formally schooled and yet were very successful. We will write a custom essay sample on Against School: A Corrupted System or any similar topic only for you Order Now According to Gatto’s, there are three main purposes to formal schooling, â€Å"1) To make good people, 2) To make good citizens, and 3) to make each person his or her best. † (Gatto 3) Gatto believes that the current educational system actually contradicts these three ideals. He claims that there are six basic yet specific functions that intend to hold back and limit the progress and overall success of a student. Of the six functions there are three serve specifically to limit and hinder a students progress. The diagnostic and directive functions, the differentiating function, and the propaedeutic function all seemingly serve to cripple a students success but when analyzed some do hold some truth but in the end they are merely irrational and ridiculous accusations made by Gatto. The diagnostic and directive functions are defined as a litmus test to test where a particular student â€Å"fits† in society based on grade percentages. These percentages are logged and stored permanently in our student records which are then passed on the post secondary schools to place students in their â€Å"proper societal roles† (4). During my freshman and sophomore years in high school I can not help but remember teachers classifying â€Å"ap† students and high academic achievers as those who were going to be â€Å"successful†. My math teacher often referred to more difficult questions as the â€Å"doctor† or â€Å"lawyer† question in an attempt to scale the difficultly of the question. What if one can not do the question? Does that mean that person should be classified as remedial or can not attain the success of a doctor or lawyer? Of course not, the simple idea of that is completely irrational. However, once reassessing and making them less extreme, Gatto’s diagnostic and directive functions can be found anywhere in the academic system whether it be perquisite knowledge for grade twelve programs or university entrance. While this function may seem absurd, Gatto’s differentiating function is one that can be related to actual everyday life. The differentiating function is a more practical function. It states that, â€Å"once a student’s role has been â€Å"diagnosed† through standardized testing, they are to be sorted by role, and trained only so far as their destination in the social machine merits. † (5) The functions practical use is especially seen in post secondary schooling where a more refined and â€Å"specialized training† takes place. We see this in any standard entry test for a specific program such as the SAT, LSAT or MCAT. Based on a students performance on these forms of testing they are then place in their respective programs allow them to focus specifically on areas of study that are important to them. At my old high school there was a standard entry test, SSAT, that examined various categories of schooling (math, reading, writing etc†¦) Depending on how you did on the test would determine not only whether or not you are eligible for acceptance but whether or not you qualify to take ap courses, because if u do not posses the proper knowledge taking a more advanced course would be counter-productive and in fact hurt your academic career. Once one has analyzed the differentiating function there is some truth to it but when one looks at the propaedeutic function, it is completely incorrect. The propaedeutic function is completely incorrect and misleading. According to Gatto, the purpose of the propaedeutic is to create a class of â€Å"elite caretakers †¦ taught to manage this project, how to watch over and control a population deliberately dumbed down and declawed† (5) He’s saying that those who already control the population are going to educate children so that when they grow up they can control the population and train more children to do the same. At this point it seems like Gatto is trying to throw something that is completely and utterly irrational out there trying to catch people off guard and hope to attract some followers. The simple thought that people were training young children to know how to manipulate people in such a way that they simply do not challenge authority and do exactly as their told to is ridiculous. At no point in my life have I ever felt that someone or an organization is trying to limit my personal abilities to comply with this absurd function. Teachers constantly enthuse student to be all they can and achieve as high as they can, not that its ok if u cant because we already got it figured out. While other of Gatto’s functions may have held some truth this particular function is completely incorrect Gatto believes that those who control the way society runs are trying to create a norm in the educational system. That student’s are pre-destined before they are given the ample chance to excel and achieve. Gatto explains that schools traditionally have three purposes: 1) To make good people; 2) To make good citizens; 3) To make each student find some particular talents to develop as best they can. These are all fine standards but because of government schools have become prison like even in there cell block style construction. Gatto’s approach is very liberal and has opened my eyes to certain matters especially the way that educational system is poorly constructed (with it being bases on grades) and how it is mismanaged leading to sub-par performance and disappointing â€Å"success† rates. It is this poorly constructed system and a corrupted way of running it is what I think Gatto was truly trying to revile. How to cite Against School: A Corrupted System, Essay examples