Protein Synthesis Transcription Translation

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DNA is the genetic material of all organism. When DNA is transmitted from parents to children, it can determine some of the children's characteristics (such as their eye color or hair color). But how does the sequence of a DNA molecule actually affect a human or other organism's features? For example, how did the sequence of nucleotides (As, Ts, Cs, and Gs) in the DNA, determine the color of their eyes or hair. • DNA is divided into functional unit called genes. Each gene provides instructions for a functional product, called protein. • Eye color gene, provides instructions for a protein that helps make colored pigments in eye. • The journey from gene to protein is complex and tightly controlled within each cell. It consists of two major steps: transcription and translation. Together, transcription and translation are known as gene expression. • During the process of transcription, the information stored in a gene's DNA is passed to a similar molecule called RNA (ribonucleic acid) in the cell nucleus. Both RNA and DNA are made up of a chain of building blocks called nucleotides, but they have slightly different chemical properties. The type of RNA that contains the information for making a protein is called messenger RNA (mRNA) because it carries the information, or message, from the DNA out of the nucleus into the cytoplasm. • RNA • RNA is chemically similar to DNA, except that it contains ribose as its sugar and substitutes the nitrogenous base uracil for thymine. An RNA molecule almost always consists of a single strand. • Stages of transcription • Transcription of a gene takes place in three stages: initiation, elongation, and termination. • 1. Initiation. At the beginning of the gene, a sequences of DNA called promoter where RNA polymerase binds. Once bound, RNA polymerase separates the DNA strands, providing the single-stranded template needed for transcription. the enzyme can “read” the bases in one of the DNA strands and make a strand of mRNA with a complementary sequence of bases. • 2. Elongation is the addition of nucleotides to the mRNA strand, making a chain that grows from 5' to 3'. • 3. Termination. Sequences of DNA, called terminators signals, that the RNA transcript is complete. Once they are transcribed, RNA polymerase detached from DNA and messenger RNA released. • Processing mRNA • the new mRNA is not yet ready for translation. At this stage, it is called pre-mRNA, and it must go through more processing. The processing may include splicing, editing, and polyadenylation. • • In messenger RNA, coding regions are known as exon and non-coding region are known as introns. Non coding regions introns should be removed, this process is known as splicing. This process is occurring by RNA-protein complex known as spliceosome, which removes the introns segments and joins the adjacent exons. • • A 5' cap is added to the beginning of the RNA transcript, and a 3' poly-A tail is added to the end. • • Now, mature messenger RNA can leave the nucleus through nuclear pore and enter the cytoplasm to begin translation. • Translation • Three nitrogenous bases are grouped into codons. The genetic code include 64 codons. Most codons for specific amino acid. There are some special codons: one that codes for start and other code for stop. • Stages of Translation • • Translation begins, when small ribosomal subunit binds at start codon in messenger RNA. • • In transfer RNA complimentary base pairs are known as anticodon which determines the specific type of amino acid. Anticodons in transfer RNA binds with codons in messenger RNA. • • When transfer RNA molecule binds with the start codon, then large ribosomal subunit binds to form translational complex • • In the large ribosomal subunit there are three distinct regions called E, P, and A sites. • • Initiating transfer RNA binds at P site. New transfer RNA binds at A site. A peptide bonds occur between amino acids. • • The complex slide down one codon to the right where the uncharged transfer RNA molecule exit from E site and A site is opened to accept the next transfer RNA molecule. • • Elongation will continue until a stop codon is reached, • • Stop codon signals the release factor binds to the A site and the polypeptide is released from the transfer RNA. • • The entire complex dissociates and can reassemble to begin the another process again. • • The polypeptides need to be modified before is ready to function. Modification is take place in different organelles for different proteins. • ‪@scienceanimation9618‬ #geneexpression #proteinsynthesis #3danimation • [email protected]

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