Dna To Rna Essay, Research Paper

DNA to RNADeoxyribonucleic acid and ribonucleic acid are two chemical substancesinvolvedin transmitting genetic information from parent to offspring. It wasknown early into the20th century that chromosomes, the genetic material of cells, containedDNA. In 1944,Oswald T. Avery, Colin M. MacLeod, and Maclyn McCarty concluded that DNAwas thebasic genetic component of chromosomes. Later, RNA would be proven toregulateprotein synthesis. (Miller, 139)DNA is the genetic material found in most viruses and in allcellular organisms.Some viruses do not have DNA, but contain RNA instead. Depending on theorganism,most DNA is found within a single chromosome like bacteria, or in severalchromosomeslike most other living things. (Heath, 110) DNA can also be foundoutside ofchromosomes. It can be found in cell organelles such as plasmids inbacteria, also inchloroplasts in plants, and mitochondria in plants and animals. All DNA molecules contain a set of linked units callednucleotides. Eachnucleotide is composed of three things. The first is a sugar calleddeoxyribose. Attachedto one end of the sugar is a phosphate group, and at the other is one ofseveralnitrogenous bases. DNA contains four nitrogenous bases. The first two,adenine andguanine, are double-ringed purine compounds. The others, cytosine andthymine, aresingle-ringed pyrimidine compounds. (Miller, 141) Four types of DNAnucleotides canbe formed, depending on which nitrogenous base is involved. The phosphate group of each nucleotide bonds with a carbon fromthedeoxyribose. This forms what is called a polynucleotide chain. James D. Watson andFrancis Crick proved that most DNA consists of two polynucleotide chainsthat aretwisted together into a coil, forming a double helix. Watson and Crickalso discoveredthat in a double helix, the pairing between bases of the two chains ishighly specific.Adenine is always linked to thymine by two hydrogen bonds, and guanine isalways linkedto cytosine by three hydrogen bonds. This is known as base pairing. (Miller, 143)The DNA of an organism provides two main functions. The firstfunction is toprovide for protein synthesis, allowing growth and development of theorganism. Thesecond function is to give all of it s descendants it s ownprotein-synthesizing informationby replicating itself and providing each offspring with a copy. Theinformation within thebases of DNA is called the genetic code. This specifies the sequence ofamino acids in aprotein. (Grolier Encyclopedia, 1992) DNA does not act directly in theprocess ofprotein synthesis because it does not leave the nucleus, so a specialribonucleic acid is usedas a messenger (mRNA). The mRNA carries the genetic information from theDNA in thenucleus out to the ribosomes in the cytoplasm during transcription. (Miller, 76)This leads to the topic of replication. When DNA replicates, thetwo strands ofthe double helix separate from one another. While the strands separate,

each nitrogenousbase on each strand attracts it s own complement, which as mentionedearlier, attacheswith hydrogen bonds. As the bases are bonded an enzyme called DNApolymerasecombines the phosphate of one nucleotide to the deoxyribose of theopposite nucleotide. This forms a new polynucleotide chain. The new DNA strand stays attachedto the oldone through the hydrogen bonds, and together they form a new DNA doublehelixmolecule. (Heath, 119) (Miller, 144-145)As mentioned before, DNA molecules are involved in a processcalled proteinsynthesis. Without RNA, this process could not be completed. RNA is thegeneticmaterial of some viruses. RNA molecules are like DNA. They have a longchain ofmacromolecules made up of nucleotides. Each RNA nucleotide is also madeup of threebasic parts. There is a sugar called ribose, and at one end of the sugaris the phosphategroup, and at the other end is one of several nitrogenous bases. Thereare four mainnitrogenous bases found in RNA. There are the double-ringed purinecompounds adenineand guanine, and there is the single-ringed pyrimidine compounds of uraciland cytosine.(Miller, 146)RNA replication is much like that of DNA s. In RNA synthesis, themoleculebeing copied is one of the two strands of a DNA molecule. So, themolecule beingcreated is different from the molecule being copied. This is known astranscription.Transcription can be described as a process where information istransferred from DNA toRNA. All of this must happen so that messenger RNA can be created, theactual DNAcannot leave the nucleus. (Grolier Encyclopedia, 1992)For transcription to take place, the RNA polymerase enzyme isneeded firstseparate the two strands of the double helix, and then create an mRNAstrand, themessenger. The newly formed mRNA will be a duplicate of one of theoriginal twostrands. This is assured through base pairing. (Miller, 147)When information is given from DNA to RNA, it comes coded. Theorigin of thecode is directly related to the way the four nitrogenous bases arearranged in the DNA. Itis important that DNA and RNA control protein synthesis. Proteins controlboth the cell smovement and it s structure. Proteins also direct production of lipids,carbohydrates, andnucleotides. DNA and RNA do not actually produce these proteins, but tellthe cell whatto make. (Heath, 111-113)For a cell to build a protein according to the DNA s request, amRNA must firstreach a ribosome. After this has occurred, translation can begin to takeplace. Chains ofamino acids are constructed according to the information which has beencarried by themRNA. The ribosomes are able to translate the mRNA s information into aspecificprotein. (Heath, 116) This process is also dependent on another type ofRNA calledtransfer RNA (tRNA). Cytoplasm contains all amino acids needed forproteinconstruction. The tRNA must bring the correct amino acids to the mRNA sothey can bealigned in the right order by the ribosomes. (Heath, 116) For proteinsynthesis to begin,the two parts of a ribosome must secure itself to a mRNA molecule. (Miller, 151)