Biology 3.05 DNA Replication PDF

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Biology 3.05 DNA Replication – Assignment _____________________________________________________________________________________ Instructions – For this assignment, you will write an essay describing the production of protein molecules through transcription and translation.

_____________________________________________________________________________________ During History, the structure of the DNA was originally discovered in 1953. Within’ a nucleotide, there are three parts which make it up, which would be the nitrogenous base, the sugar molecule, and the phosphate molecule. The nucleotide would be the group that repeats constantly in order to create large molecules of the DNA. Composed of the nitrogenous bases, Adenine, Guanine, Thymine, and Cytosine, the strands of DNA are complementary, meaning that if you were to only know the bases of one side of the ladder, you would always be able to tell the other side of the ladder’s bases, because all of the bases each have a pair. For example, Adenine pairs with Thymine, whilst Guanine pairs with Cytosine, and these bases cannot be switched around, therefore, you’d know the bases of the other ladder. During the process where the DNA makes copies of itself, it is called “DNA Replication”, which takes place in the nucleus of the cell. For this to work, the DNA double helix is “unzipped”, whilst an enzyme known as the DNA helicase starts to attach to the DNA molecule, which would be the double helix. Following this, the enzyme moves along the molecule, which then it unzips the two strands of DNA, by breaking the bond which holds the Adenine and Thymine together, being the hydrogen bond. The complementary nucleotides which are floating around within’ the nucleus signals that Adenine, Guanine, Thymine, and Cytosine are still floating within’ the nucleus, and so these bases make the hydrogen bonds with the bases inside of the DNA strands. After this, the enzyme known as the “DNA polymerase” creates the formation for the sugar phosphate units which are along the side of the “ladder” (the bases) and then they connect one base pair to the next, which results into two new DNA molecules, due to the replication, where each molecule has a strand of the new DNA, as well as the old DNA. Small organelles which are found in the cytoplasm which manufactures proteins would be the ribosome. The RNA however, is a nucleic acid, which is somewhat like the DNA, but rather instead of having two strands, it has single stranded. Even with this difference, they both use the same nitrogenous bases, except for the DNA having Thymine and the RNA having Uracil. For the RNA, instead of the Adenine binding to the Thymine, it rather binds with the Uracil. During the process of transcription (which is the first step in the process of getting instructions off the DNA and out into the cytoplasm), the DNA (like before during the cell replication) unzips, where one of the strands are then transcribed by the enzyme, which is then in turn used to make a messenger RNA (mRNA) molecule, which uses the base Uracil instead of Thymine to bind Adenine. After this, the coding which the messenger RNA molecule carries has a sequence of three nucleotides, which is called a “codon” which is considered “a three-letter word that selects for amino acid”. The messenger RNA will then bring the instructions from the nucleus to the cytoplasm. After this, once the messenger RNA (mRNA molecule) has managed to transcribe the message, it then breaks apart from the DNA strand, and then allows the DNA to rezip back up to its normal shape, which is the helix shape. Once the messenger RNA manages to leave the nucleus, it happens to float within’ the cytoplasm, where there are also different types of RNA molecules located, which are called transfer RNA molecules (tRNA), where this molecule has three nucleotide codes on one end, whilst there is a different, specific kind of amino acid for the latter end. Following this step for the translation, within’ the cytoplasm, the messenger RNA which attracts the ribosome w/ molecules that also have the same or matching three letter code (like codon for example) manage to form a temporary bond with the messenger RNA, which then allow the amino acids on the transfer RNA molecules to also bond, which constructs a protein chain. After this, the growing chain Is finished, only once a stop codon is reached, which then the chain which is completed breaks away. Hence, the chain of amino acids which had been broken off would be the completed protein which was made....