Polypeptide Synthesis of a DNA Sequence

[Audio] Polypeptide Synthesis of a DNA Sequence ABOUT DNA DAY Understanding Transcription and Translation. Made by: Mohamed and Nabil..

[Audio] What is Transcription? Transcription is the process by which a cell copies information from DNA to make messenger RNA (mRNA). ABOUT DNA DAY.

[Audio] Where Transcription Occurs Transcription happens in the nucleus, a small compartment inside the cell where DNA is stored. DNA is the instruction manual for making everything in the body, but it never leaves the nucleus. This is because DNA is very big and it cannot exit the nucleus. Instead, the cell makes a temporary copy of a specific section of DNA in the form of mRNA, which can leave the nucleus. This is important because the rest of the cell, including the ribosomes that make proteins, is outside the nucleus. mRNA acts as the messenger that carries the instructions from DNA to the ribosomes..

[Audio] Transcription Transcription is how a cell makes a copy of its DNA instructions into a message called mRNA, which can leave the nucleus. It starts with initiation, where an enzyme called RNA polymerase attaches to a specific starting point on the DNA, called the promoter. The DNA then unwinds and opens up, exposing one strand, called the template strand, which will be copied. In the next step, called elongation, RNA polymerase reads the DNA bases on the template strand and matches them with their RNA partners For example, if the DNA has "A," the RNA will have "U," and if the DNA has "G," the RNA will have "C." This builds a long strand of mRNA that grows as RNA polymerase moves along the DNA. Finally, in termination, RNA polymerase reaches a stopping point called the terminator. At this point, the mRNA is complete, it detaches from the DNA, and the DNA closes back up. Before the mRNA leaves the nucleus, it gets a "cap" on one end and a "tail" on the other to protect it and help it work. The mRNA then travels to the cytoplasm to be used for making proteins..

[Audio] Transcription of polypeptide synthesis This image shows transcription, the first step in polypeptide synthesis, where the genetic information in DNA is used to create a complementary strand of messenger RNA (mRNA). This process occurs in the nucleus, where DNA is stored and protected. Transcription ensures that the instructions for making proteins are safely copied into a form that can leave the nucleus and direct protein synthesis in the cytoplasm. At the top of the image, the DNA double helix is shown. DNA is made up of two strands, tightly wound together, and it contains all the instructions for building proteins. During transcription, a specific section of DNA (a gene) is unzipped, and the two strands separate. This exposes the template strand, which will be used to create the mRNA. The other strand, called the coding strand, is not involved in the process. In the middle of the image, the enzyme RNA polymerase begins reading the DNA template strand. It builds a complementary strand of mRNA by matching the bases in DNA to their RNA counterparts: DNA base A pairs with RNA base U (uracil replaces thymine in RNA). DNA base T pairs with RNA base A. DNA base C pairs with RNA base G. DNA base G pairs with RNA base C. This step produces an immature mRNA strand, shown as the green strand in the image. At the bottom of the image, the immature mRNA strand is nearly complete. Once transcription is finished, the mRNA will undergo some modifications to become mature mRNA, such as adding a 5' cap and a poly-A tail. The mRNA then exits the nucleus (indicated by the arrow) and enters the cytoplasm, where the second stage of polypeptide synthesis, translation, will occur..

[Audio] How DNA Unzips DNA is normally a double stranded molecule, like a twisted ladder, with the two strands tightly wound together. For transcription to begin, these two strands need to be separated so the cell can read the information on one of the strands. Here’s how it happens: 1. A special enzyme called RNA polymerase binds to a region of the DNA called the promoter. This promoter acts like a signal to tell the RNA polymerase where to start. 2. RNA polymerase unzips the DNA by breaking the weak bonds between the base pairs. The two strands of DNA separate, exposing the bases on one strand 3. The strand of DNA that is used to create mRNA is called the template strand. The other strand, which is not used, is called the coding strand..

[Audio] Features of mRNA Single stranded: mRNA is made up of just one strand, unlike DNA, which has two strands. This makes it smaller and easier to move out of the nucleus to the ribosome. Uracil instead of Thymine: In mRNA, the base uracil is used instead of thymine , which is found in DNA .For example, when DNA has an adenine , mRNA pairs it with uracil instead of Thymine Codons :mRNA is divided into groups of three bases, called codons. Each codon acts like a "code" that tells the ribosome which amino acid to add to the protein..

[Audio] How mRNA is Formed To understand how mRNA is formed, think of it like copying instructions from a book (DNA) to make a single-page guide (mRNA) that can leave the library (nucleus) and be used elsewhere (ribosome). Here’s how the process works: first step, Initiation: 1. A special enzyme called RNA polymerase unzips a section of the DNA called a gene into two strands called the template strand and the coding strand. 2. This then allows for the enzyme, RNA polymerase, to read the exposed bases on the template strand 3. The enzyme brings in nucleotides of Adenine, Guanine, Cytosine, and Uracil to the template strand so that they can form a mature mRNA.

[Audio] Second step, Elongation: (Building the mRNA) RNA polymerase moves along the template strand of the DNA, reading it one base at a time. It matches the DNA bases with their complementary RNA bases RNA polymerase continues adding RNA bases to build the mRNA strand. Step 3, Termination (Stopping the Process) RNA polymerase keeps moving until it reaches a specific DNA sequence called the terminator sequence. The terminator is like a "stop signal" that tells RNA polymerase to stop copying. Once RNA polymerase stops, it releases the newly made mRNA strand, and the DNA closes back up..

[Audio] What is translation ? Translation is the process of converting the information in mRNA into a polypeptide chain, which eventually folds into a functional protein. This process is essential for protein synthesis and occurs after transcription..

[Audio] Why is Transcription Important? Transcription is a critical step in protein synthesis because it converts the permanent instructions stored in DNA into a temporary, usable form (mRNA). The mRNA carries the genetic code out of the nucleus and ensures that the cell can make proteins, which are essential for structure, function, and regulation in the body. Without transcription, the cell could not produce proteins, and life would not be possible. ABOUT DNA DAY.

[Audio] The Role of Enzymes in Transcription Enzymes are essential for transcription, and the most important one is RNA polymerase. RNA Polymerase: This enzyme does everything during transcription. It: Binds to the promoter region. Unwinds and separates the DNA strands. Adds complementary RNA bases to build the mRNA strand. Stops transcription at the terminator sequence..

[Audio] Where Translation Occurs Translation happens in the cytoplasm of the cell. The site of translation is a structure called the ribosome. Ribosomes are found either floating freely in the cytoplasm or attached to the rough endoplasmic reticulum The ribosome reads the sequence of codons on the mRNA and assembles the amino acids in the correct order to form a polypeptide chain..

[Audio] The Role of Ribosomes Ribosomes are the machines that carry out translation. They are made of two parts: a small subunit and a large subunit. Functions of Ribosomes: 1. Bind to mRNA: The ribosome attaches to the mRNA and positions it so it can be read in groups of three bases (codons). 2. Facilitate tRNA Binding: The ribosome helps tRNA molecules bring amino acids to the correct position. 3. Build the Polypeptide Chain: The ribosome links amino acids together by forming peptide bonds between them. Think of the ribosome as a factory assembly line it organizes the raw materials (amino acids) and puts them together to create the finished product (polypeptide)..

[Audio] The Role of mRNA mRNA (Messenger RNA) carries the genetic instructions from the DNA to the ribosomes . It contains codons, which are groups of three bases that correspond to specific amino acids. How it works: The ribosome reads each codon on the mRNA, starting at the start codon. Each codon tells the ribosome which amino acid to add to the growing polypeptide chain. The sequence of codons determines the order of amino acids in the protein..

[Audio] The role of tRNA Transfer RNA (tRNA) plays a key role in translation by delivering specific amino acids to the ribosome. Each tRNA molecule contains an anticodon that pairs with the complementary codon on the mRNA, ensuring the correct sequence of amino acids is added to the growing polypeptide chain. This process ensures accurate protein synthesis based on the genetic instructions in the mRNA..

[Audio] Translation of polypeptide synthesis This image represents translation, the second step in polypeptide synthesis, which occurs in the cytoplasm at the ribosome. During translation, the ribosome reads the mRNA (blue strand) in groups of three bases called codons. Each codon matches with a specific tRNA molecule, which carries an amino acid (colored circles) to the ribosome. The anticodon on the tRNA pairs with the complementary codon on the mRNA, ensuring the correct amino acid is added to the growing chain. The ribosome forms peptide bonds between the amino acids, creating a polypeptide chain. As the ribosome moves along the mRNA, the chain grows longer until a stop codon is reached, signaling the end of translation. This process assembles the polypeptide in the correct order, based on the instructions in the mRNA, and ensures accurate protein synthesis..

[Audio] Polypetide synthesis and how its formed. Polypeptide synthesis is the process by which proteins are made in nucleus, involving two key stages: transcription and translation. During transcription, which occurs in the nucleus, the DNA sequence of a gene is copied into mRNA, which then carries the genetic instructions to the cytoplasm. In translation, the mRNA binds to a ribosome, where it is read in codons (groups of three bases). Each codon matches with a complementary anticodon on a tRNA molecule, which delivers the corresponding amino acid. The ribosome links these amino acids together through peptide bonds, forming a polypeptide chain. This chain folds into a functional protein. The collaboration of DNA, mRNA, tRNA, ribosomes, and amino acid ensures that polyptide synthesis produces the protein and make sure that its accurate and functional which is essential for cell function ..

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