Transcription is a process in which RNA is synthesised from a DNA template. Transcription occurs inside the nucleus of eukaryotic cells and is catalysed by the enzyme RNA polymerase. The enzyme catalyses the initiation and elongation of RNA chains and requires a DNA template, all four ribonucleoside triphosphates (ATP, GTP, CTP and UTP) and a divalent metal ion such as Mg2+ or Mn2+ (Burrell, H, 2014).
Transcription is split into three stages; initiation, elongation and termination. During initiation of transcription RNA polymerase binds to the promoter and just 17 base pairs of DNA are unwound at any given time. Figure 1 shows RNA polymerase attached to the DNA strand and 17 base pairs that have been separated (Burrell, H, 2014).
During the
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Stop codons designate chain termination and are read by specific proteins known as release factors. When the release factor binds to the ribosome the newly synthesised protein is released from the ribosome.
In prokaryotic cells transcription is performed by a single type of RNA polymerase, compared to three different types in eukaryotic cells (Clancy, S, 2008). During the initiation of transcription in bacterial cells the promoter must initially be bound by a polymerase. In this binding, the promoter sequence is in competition with other promoters and non-specific sites on the DNA. Second, the polymerase must move through the initiation phase of transcription into elongation as rapidly as possible to ‘clear’ the promoter and make it available for reuse (Brown, W and Brown, P, 2002).
As shown in Figure 2 RNA polymerase contains two α polypeptides, one β polypeptide, and one β′ polypeptide. The addition of the σ subunit (sigma factor) allows initiation at promoter regions (Griffiths, A.J.F et al. 2000). Sigma factors are used during initiation of transcription in prokaryotic cells and enable RNA polymerase to bind to promoter regions. Several distinct sigma factors have been identified and each of these oversees transcription of a unique set of genes (Clancy, S,
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The next amino acyl-tRNA binds to the exposed codon in the A site of the ribosome. A peptide bond is formed between the two adjacent amino acids and linked amino acids are attached to the tRNA in the A site, forming a peptidyl-tRNA. Translocation then occurs as the ribosome moves one codon to the right and the peptidyl-tRNA moves from the A site to the P site. Uncharged tRNA moves from the P site to the E site. When translocation is complete uncharged tRNA is released from the E site and the ribosome is ready for another elongation cycle (Burrell, H,
There are many different cells that do many different things. But all of these cells fall into two categories: prokaryotic and eukaryotic cells. Eukaryotic cells contain a nucleus and are larger in size than prokaryotic cells. Prokaryotic cells do not contain a nucleus, are smaller and simpler than eukaryotic cells. Two of their similarities are they both have DNA as their genetic material and are covered by a cell membrane. Two main differences between these two cells are age and structure. It is believed that prokaryotic cells were the first forms on earth. They are considered primitive and originated approximately 3.5 billion years ago. Eukaryotic cells have only been around for about a billion years. There is strong evidence that suggests eukaryotic cells may be evolved from groups of prokaryotic cells that became interdependent on each other (Phenotypic analysis. (n.d.).
coli after addition of inducer IPTG at different times. We can see from the graph that it does not cut the X axis at time 0. This is due to the fact that the lac operon was not induced by IPTG due to lack of time. The graph cuts the X axis at roughly 1 and a half minutes after adding IPTG. This indicates the time where lac operon was first induced because there was beta-galactosidase produced. From here we can deduce that production of beta-galactosidase does not take place immediately after adding IPTG but rather takes a while for all the expression staged to be passed by lac operon in order to produce beta galactosidase. From the graph we can see that for the control no beta galactosidase was produced. This is because the control contains water and the repressor was allowed to bind to the operator, causing the transcription process to initiate due to RNA polymerase II not binding to the operator. There is a positive linear relationship between the time of induction with IPTG and the amount of beta-galactosidase production in the tubes. IPTG acts as an inducer, stopping the repressor protein to bind to the operator region by binding to the repressor protein, This causes the lac operon to be
Miller, Kenneth R. and Joseph S. Levine. “Chapter 12: DNA and RNA.” Biology. Upper Saddle River: Pearson Education, Inc., 2002. Print.
In order to do this a polymer of DNA “unzips” into its two strands, a coding strand (left strand) and a template strand (right strand). Nucleotides of a molecule known as mRNA (messenger RNA) then temporarily bonds to the template strand and join together in the same way as nucleotides of DNA. Messenger RNA has a similar structure to that of DNA only it is single stranded. Like DNA, mRNA is made up of nucleotides again consisting of a phosphate, a sugar, and an organic nitrogenous base. However, unlike in DNA, the sugar in a nucleotide of mRNA is different (Ribose) and the nitrogenous base Thymine is replaced by a new base found in RNA known as Uracil (U)3b and like Thymine can only bond to its complimentary base Adenine. As a result of how it bonds to the DNA’s template strand, the mRNA strand formed is almost identical to the coding strand of DNA apart from these
The study of nucleic acids has now become a fruitful and dynamic scientific enterprise. Nucleic acids are of unique importance in biological systems. Genes are made up of deoxyribonucleic acid or DNA, and each gene is a linear segment, or polymer, of a long DNA molecule. A DNA polymer, or DNA oligonucleotide, contains a linear arrangement of subunits called nucleotides. There are four types of nucleotides. Each nucleotide has three components; a phosphate group, a sugar and a base that contains nitrogen within its structure. The sugar moiety in DNA oligonucleotides is always dexoyribose, and there are four alternative bases: adenine (A), thymine (T), guanine (G), and cytosine (C). The phosphate groups and the deoxyribose sugars form the backbone of each DNA stand. The bases are joined to the deoxyribose sugar and stick out to the side. Both oligomers, DNA and RNA, consist of 5’->3’ phosphodiester-linked nucleotide units that are composed of a 2’-deoxy-D-ribose (DNA) or D-ribose (RNA) in their furanose forms and a heteroaromatic nucleobase (A, T, G, and C; A, U, G, C), and the resulting oligonucleotide chain is composed of a polar, negatively charged sugar-phosphate backbone and an array of hydrophobic nucleobases. The amphiphilic nature of these polymers dictates the assembly and maintenance of secondary and tertiary structures the oligonucleotides can form. In the DNA duplex structure, genetic information is stored as a linear nucleotide code. This code can be accessed and replicated. RNA, or ribonucleic acid, is another structurally related essential biopolymer. RNA differs from DNA in having the sugar ribose in place of the deoxyribos...
Also in a PRC reaction, DNA Polymerase is made of many complicated proteins with the function of duplicating DNA before division occurs (2).
Since DNA has the instructions for making the proteins, but it has to be highly protected, it doesn’t leave the nucleus where it is mostly found (Hall, 6). DNA’s function is to be a long-term storage and transmission of the genetic information (DNA vs RNA, 2014). Copies of certain instructions needed for proteins can be made in the form of RNA. It’s not an exact copy of what is found in DNA, but RNA can travel out of the nucleus with the instructions. RNA make...
... the codon for the amino acid methionine is added the head of each chain.
In humans and other eukaryotes, there is an extra step. RNA polymerase can attach to the promoter only with the help of proteins called basal (general) transcription factors. They are part of the cell's core transcription toolkit, needed for the transcription of any
At the beginning at the primer sequence, the DNA polymerase attaches to the original DNA strand and begins assembling a complementary strand.
Citation: Philips, T. (2008) Regulation of Transcription and gene expression in Eukaryotes. Nature Education 1(1)
Secondly the gene has to be cut from its DNA chain. Controlling this process are many restriction endonucleases (restriction enzymes). Each of these enzymes cut DNA at a different base sequence called a recognition sequence. The recognition sequence is 6 base pairs long. The restriction enzymes PstI cuts DNA horizontally and vertically to produce sticky ends.
Discoveries in DNA, cell biology, evolution, and biotechnology have been among the major achievements in biology over the past 200 years with accelerated discoveries and insight’s over the last 50 years. Consider the progress we have made in these areas of human knowledge. Present at least three of the discoveries you find to be the most important and describe their significance to society, heath, and the culture of modern life.
There are four main levels of a protein, which make up its native conformation. The first level, primary structure, is just the basic order of all the amino acids. The amino acids are held together by strong peptide bonds. The next level of protein organization is the secondary structure. This is where the primary structure is repeated folded so that it takes up less space. There are two types of folding, the first of which is beta-pleated sheets, where the primary structure would resemble continuous spikes forming a horizontal strip. The seco...
During this phase the DNA aka “deoxyribose nucleic acid” clone then forms chromatin. Chromatin is the mass of genetic material that forms into chromosomes. Interphase is divided into smaller parts: G1 Phase, S phase and G2 Phase. Throughout all the phases, the cells continuously develop by producing mitochondria, endoplasmic reticulum, and proteins. The actual division occurs during the S phase bur the G phases are mainly for the purpose of growing. Starting with the G1 phase the cell grows in preparation for certain intracellular components and DNA replication. This phase makes sure the cell is prepared for the process of DNA replication. It reviews the size and environment to ensure that is it ready to go, and cannot leave the G1 until it is complete. But what happens to a cell when it is not complete and cannot exit out of the phase? It will pause and transfer to phase G0. There’s no certain time to be in this phase but it will remain until it reaches the fitting size and is in a supportive surroundings for DNA replication. It will exit either G1 or G0 and there is no other way besides these. Then the cell will advance to the next phase which is the S phase. Synthesis, or more known as S phase is the section of the cell cycle when the DNA is wrapped into chromosomes then duplicated. This is a very important part of the cycle because it grants each of them that is created, to have the exact same genetic