The Cystic Fibrosis Gene Essays - Cystic Fibrosis, Protein Families

The Cystic Fibrosis Gene Essays - Cystic Fibrosis, Protein Families The Cystic Fibrosis Gene Biology - Genetics The Cystic Fibrosis Gene Introduction: Cystic fibrosis is an inherited autosomal recessive disease that exerts its main effects on the digestive system and the lungs. This disease is the most common genetic disorder amongst Caucasians. Cystic fibrosis affects about one in 2,500 people, with one in twenty five being a heterozygote. With the use of antibiotics, the life span of a person afflicted with CF can be extended up to thirty years however, most die before the age of thirteen.1 Since so many people are affected by this disease, it's no wonder that CF was the first human genetic disease to be cloned by geneticists. In this paper, I will be focusing on how the cystic fibrosis gene was discovered while at the same time, discussing the protein defect in the CF gene, the bio-chemical defect associated with CF, and possible treatments of the disease. Finding the Cystic Fibrosis Gene: The classical genetic approach to finding the gene that is responsible for causing a genetic disease has been to first characterize the bio-chemical defect within the gene, then to identify the mutated protein in the gene of interest, and finally to locate the actual gene. However, this classical approach proved to be impractical when searching for the CF gene. To find the gene responsible for CF, the principle of "reverse genetics" was applied. Scientists accomplished this by linking the disease to a specific chromosome. After this linkage, they isolated the gene of interest on the chromosome and then tested its product.2 Before the disease could be linked to a specific chromosome, a marker needed to be found that would always travel with the disease. This marker is known as a Restriction Fragment Length Polymorphism or RFLP for short. RFLP's are varying base sequences of DNA in different individuals which are known to travel with genetic disorders.3 The RFLP for cystic fibrosis was discovered through the techniques of Somatic Cell Hybridization and through Southern Blot Electrophoresis (gel separation of DNA). By using these techniques, three RFLP's were discovered for CF; Doc RI, J3.11, and Met. Utilizing in situ hybridization, scientists discovered the CF gene to be located on the long arm of chromosome number seven. Soon after identifying these markers, another marker was discovered that segregated more frequently with CF than the other markers. This meant the new marker was closer to the CF gene. At this time, two scientists named Lap-Chu Tsui and Francis Collins were able to isolate probes from the CF interval. They were now able to utilize to powerful technique of chromosome jumping to speed up the time required to isolate the CF gene much faster than if they were to use conventional genetic techniques.3 In order to determine the exact location of the CF gene, probes were taken from the nucleotide sequence obtained from chromosome jumping. To get these probes, DNA from a horse, a cow, a chicken, and a mouse were separated using Southern Blot electrophoresis. Four probes were found to bind to all of the vertebrate's DNA. This meant that the base pairs within the probes discovered contained important information, possibly even the gene. Two of the four probes were ruled out as possibilities because they did not contain open reading frames which are segments of DNA that produce the mRNA responsible for genes. The Northern Blot electrophoresis technique was then used to distinguish between the two probes still remaining in order to find out which one actually contained the CF gene. This could be accomplished because Northern Blot electrophoresis utilizes RNA instead of DNA. The RNA of cell types affected with CF, along with the RNA of unaffected cell types were placed on a gel. Probe number two bound to the RNA of affected cell types in the pancreas, colon, and nose, but did not bind to the RNA from non-affected cell types like those of the brain and heart. Probe number one did not bind exclusively to cell types from CF affected areas like probe number two did. From this evidence, it was determined that probe number two contained the CF gene. While isolating the CF gene and screening the genetic library made from mRNA (cDNA library), it was

Definition and Examples of Exclamatory Sentences

Definition and Examples of Exclamatory Sentences In English grammar, an exclamatory sentence is a type of main clause  that expresses strong feelings by making an exclamation. Compare this with sentences that make a statement  (declarative sentences), express a command  (imperative sentences), or ask a question  (interrogatory sentences). An exclamatory sentence is also called an  exclamative or an exclamative clause. An exclamatory sentence usually ends with an exclamation point  (!). With the appropriate intonation, other sentence types- especially declarative sentences- can be used to form exclamatives.   Adjectives in  Exclamatory Phrases and Clauses Exclamatory phrases can stand on their own as sentences- such as if someone says No way! or uses interjections such as Brrr!- without even needing to have a subject and a verb in them, though to qualify as an exclamatory clause or sentence, a subject and verb need to be present. Author Randolph Quirk and his colleagues explain how adjectives play a part in creating exclamatory phrases and clauses: Adjectives (especially those that can be complement when the subject is eventive, eg: Thats excellent!) can be exclamations, with or without an initial wh-element...:​  Excellent! (How) wonderful!...Such adjective phrases need not be dependent on any previous linguistic context but may be a comment on some object or activity in the situational context. (​A Comprehensive Grammar of the English Language. Longman, 1985) Interrogative Clauses as Exclamations In addition to sentences that have the typical declarative  subject-verb  structure, there are exclamatory sentences that take a positive or negative interrogative structure. For example, examine the sentence structure here: Oh wow, was that a great concert! Note that the verb was comes before the subject concert. If youre having trouble parsing out subjects for these type of sentences, look first for the verb and then find the subject by deciding what belongs to the verb. Here, its concert, as you could put the sentence in a subject-verb order as Oh wow, that concert was great!   There are exclamatory questions, too, such as, Isnt this fun! or Well, what do you know! And there are rhetorical questions of surprise, such as What?! that end with both a question mark and an exclamation point.   Avoid Overuse in Your Writing Exclamative types of sentences rarely appear in  academic writing, except when theyre part of  quoted  material, which would likely be rare in that field. Please be aware that overuse of exclamations and exclamation points in  essays, nonfiction articles, or in fiction is a sign of amateurish writing. Use them only when absolutely necessary, such as  in direct  quotes and dialogue. Even then, revise out what you can in order to leave only the most necessary. Dont allow exclamation points (and exclamatory sentences) to become a crutch to carry the emotion of a scene. In fiction, the words the characters speak and the tension in the scene driven by the narration should be what expresses the emotion. The author voice  in an essay or nonfiction article should carry the message; exclamations should be restricted to direct quotes attributed to sources. A good rule of thumb to follow for any piece of writing is to allow only one exclamation point for every 2,000 words (or more, if possible). Revising them out of your drafts will make your overall piece stronger by the time its finalized.