Summary Of Assignment: 05 DNA Replication

The small ribosomal subunit, amongst other things, is initiates the engagement of the mRNA and is responsible decoding the genetic information during translation [4].

Transcription is the formation of an RNA strand from a DNA template within the nucleus of a cell. There are four nucleotides of DNA. These are adenine, cytosine, guanine and thymine. These nucleotides are transcribed to form messenger ribonucleic acid (mRNA) consisting of nucleotides made of adenine, cytosine, guanine and uracil. This transcription from DNA to mRNA happens by an RNA polymerase II. This newly created mRNA is read in the 5' to 3' direction in sets of 3. These sets are called codons. Each mRNA also has a cap and end. On the 5 prime side is a methylated guanine triphosphate and on the 3 prime is a poly A tail. Messenger RNA then moves to the cells cytoplasm and through the cells ribosomes for translation. Messenger RNA is matched to molecules of transfer RNA (tRNA) in the ribosomes to create amino acids. These amino acids subsequently form an amino acid chain. (Osuri, 2003) A visual representation of this can been viewed in figure 3.

After the DNA has been turned into mRNA a process called translation occurs and it turns the mRNA into tRNA.

The genetic code has 64 codons, which codes for 20 amino acids. Redundancies of the genetic code allow different variation of codons to code for the same amino acids. The benefit of this is that even if there is a mistake in the base pairing, the amino acid might be unaffected. This allows amino acids to be represented in more than one combination.

The virus fuses with the cell’s plasma membrane. The capsid proteins are removed, releasing the viral proteins and RNA. Reverse transcriptase catalyzes the synthesis of a DNA strand complementary to the viral RNA. Reverse transcriptase catalyzes the synthesis of a second DNA strand complementary to the first. The double-stranded DNA is incorporated as a provirus into the cell’s DNA. Proviral genes are transcribed into RNA molecules, which serve as genomes for the next viral generation and as mRNAs for translation into viral proteins. The viral proteins include capsid proteins and reverse transcriptase (made in the cytosol) and envelope glycoproteins (made in the ER). Vesicles transport the glycoproteins from the ER to the cell’s plasma membrane. Capsids are assembled around viral genomes and reverse transcriptase molecules. New viruses bud off from the host cell.

The primary structure of a protein is a specific linear sequence of amino acids, it determines the final 3D structure. These amino acids form a covalent bond via peptide bonds between the nitrogen on the α-amino group on one amino acid and the oxygen from the α-carboxyl group of another. This joining of two or more amino acids to for a polypeptide chain is known as a condensation reaction in which a molecule of water is removed, Figure 1. The ends of a polypeptide have specific names, the end with a free amino group is referred to as the N-terminal, whereas

During this lab the Drosophila cells had to go through certain processes so we could insert the double stranded RNA. The first process is replication. Replication is a semiconservative process in which two strands of DNA are created from one double strand of DNA. The total production is four single strands of DNA, each strand made from one old and one newly made single strand. Replication first starts with a cluster of proteins called a protein complex. When a protein complex binds to a section of DNA with adenine and thymine repeats, called regions of replication, it creates a ‘bubble’ between the DNA. With a small opening in the DNA an enzyme called helicase comes in and makes the bubble larger. In order to keep the DNA from joining back together a protein binds to the open DNA. Primase, another enzyme, lays down little strands of RNA for an enzyme called DNA polymerase III to bind to so it can add new complementary nucleotides to create a new segment of single stranded DNA. DNA Polymerase III can only work

The siRNA directs RISC to the target mRNA. RISC uses the siRNA guide strand to bind to a certain target site of mRNA. The siRNA and the mRNA have complementary sequence which is determined by base pairing. The target mRNA is then cut and split when bound to Argonaut and is then degraded. The siRNA completely eliminates the mRNA as it is degraded. The mRNA is needed to for the translation process so without the mRNA the protein would not be produced.

Protein synthesis is the manufacturing of functional polypeptides in the cytoplasm. Protein synthesis occurs through the process of translation. Translation is the formation of a chain of amino acids by using the instructions a messenger RNA strand provides. This process takes place at the ribosome. The codons of an mRNA strand carry the instructions in triplets of bases of the coding strand of the gene. Each codon encodes a specific amino acid to be installed into the growing polypeptide chain. During translation, the sequence of codons will dictate the sequence of amino acids in the protein. The amino acids are delivered to the ribosome by transfer RNA, a fairly small and mobile type of RNA. Each transfer RNA molecule attaches and transports a specific amino acid.

Then the pre-initiation complex is form at the TATA box. Then uses cellular DNA-dependent RNA polymerase mediated transcription at the viral promoter site. During transcription mRNAs are capped and poly-adenylation by host enzymes. Then mRNAs are transported to the cytoplasm for translation into early proteins and migrate back to the nucleus, which mediates viral DNA replication4.

Translation involves the mRNA binding to ribosomes in the cytoplasm of the muscle cell. Here, transfer RNA, or tRNA, molecules also bind to the ribosome. The order

To prevent incorrect amino acid joining to a tRNA, an editing domain is required. The 3.90.740.10 (connecting-peptide domain) is a post-transfer editing and proofreading domain, which hydrolyses the misacylated tRNA, and is found in ValRS, IleRS and LeuRS. For example, isoleucine is larger than valine by just one methyl group, therefore these aaRS’s need to distinguish between the smaller amino acids to ensure the correct amino acid is transferred to the tRNA. The 3.90.740.10 domain is inserted into the catalytic core and if valine enters the editing domain, it will be hydrolysed and broken down, as is too small to accommodate the binding of isoleucine (Arnez. J, 2009). 1.10.730.10 (Orthogonal bundle) is another example of an editing domain, and helps with the binding of the correct bases to the anticodon (Sugiura et al.

In translation, a mRNA, the messenger, is decoded and the information that comes from it. It is used to form chains of amino acid. The instructions of information that is used to build the amino acid chains are called codons. Codons are 3 nucleotides and there are a start and stop codons which signal the progress of the chains. The codons are read in order by tRNA, the transfer, each tRNA has an anticodon. The last thing that happens is the chains of amino acids are released into the cell when they reach a stop codon and they go do their own job in the cell.

Ribosome assembly begins with transcription of pre‐rRNA. During transcription, ribosomal and non‐ribosomal proteins attach to the rRNA.10

Transcription is where DNA is transcribed into RNA which then can be pass to the ribosome’s to act as a template for protein synthesis. Before transcription can begin DNA must unwind and the two halves of the molecule much come apart so exposing the base sequence. This process begins when a region of a two DNA strands is unzipped by enzyme called RNA polymerase attaches to the DNA molecule at the imitation site.