Search results
Jul 31, 2022 · As with mRNA synthesis, protein synthesis can be divided into three phases: initiation, elongation, and termination. The process of translation is similar in prokaryotes and eukaryotes. Here we’ll explore how translation occurs in E. coli, a representative prokaryote, and specify any differences between prokaryotic and eukaryotic translation.
Dec 27, 2023 · The canonical structure of DNA has four bases: thymine (T), adenine (A), cytosine (C), and guanine (G). DNA sequencing is the determination of the physical order of these bases in a molecule of DNA. However, DNA bases are often modified by epigenetic processes to control gene expression.
During translation, which is the second major step in gene expression, the mRNA is "read" according to the genetic code, which relates the DNA sequence to the amino acid sequence in...
People also ask
What are the three stages of DNA translation?
What are aminoacyl tRNA synthetases?
How does chloramphenicol affect translation?
What is DNA synthesis?
Apr 8, 2024 · Translation is the process by which the genetic code contained within a messenger RNA (mRNA) molecule is decoded to produce a specific sequence of amino acids in a polypeptide chain. It occurs in the cytoplasm following DNA transcription and, like transcription, has three stages: initiation, elongation, and termination.
- Overview
- Introduction
- The genetic code
- Overview of translation
- Transfer RNAs (tRNAs)
- Ribosomes
- Steps of translation
- Getting started: Initiation
- Extending the chain: Elongation
- Finishing up: Termination
How the nucleotide sequence of an mRNA is translated into the amino acid sequence of a polypeptide (protein).
•Step 1: transcription! Here, the DNA sequence of a gene is "rewritten" in the form of RNA. In eukaryotes like you and me, the RNA is processed (and often has a few bits snipped out of it) to make the final product, called a messenger RNA or mRNA.
•Step 2: translation! In this stage, the mRNA is "decoded" to build a protein (or a chunk/subunit of a protein) that contains a specific series of amino acids.
[What exactly is an "amino acid"?]
Take a moment to look at your hands. The bone, skin, and muscle you see are made up of cells. And each of those cells contains many millions of proteins1 . As a matter of fact, proteins are key molecular "building blocks" for every organism on Earth!
How are these proteins made in a cell? For starters, the instructions for making proteins are "written" in a cell’s DNA in the form of genes. If that idea is new to you, you may want to check out the section on DNA to RNA to protein (central dogma) before getting into the nitty-gritty of building proteins.
Basically, a gene is used to build a protein in a two-step process:
•Step 1: transcription! Here, the DNA sequence of a gene is "rewritten" in the form of RNA. In eukaryotes like you and me, the RNA is processed (and often has a few bits snipped out of it) to make the final product, called a messenger RNA or mRNA.
•Step 2: translation! In this stage, the mRNA is "decoded" to build a protein (or a chunk/subunit of a protein) that contains a specific series of amino acids.
[What exactly is an "amino acid"?]
During translation, a cell “reads” the information in a messenger RNA (mRNA) and uses it to build a protein. Actually, to be a little more techical, an mRNA doesn’t always encode—provide instructions for—a whole protein. Instead, what we can confidently say is that it always encodes a polypeptide, or chain of amino acids.
[Wait, what is the difference?]
In an mRNA, the instructions for building a polypeptide are RNA nucleotides (As, Us, Cs, and Gs) read in groups of three. These groups of three are called codons.
There are 61 codons for amino acids, and each of them is "read" to specify a certain amino acid out of the 20 commonly found in proteins. One codon, AUG, specifies the amino acid methionine and also acts as a start codon to signal the start of protein construction.
How is an mRNA "read" to make a polypeptide? Two types of molecules with key roles in translation are tRNAs and ribosomes.
Transfer RNAs, or tRNAs, are molecular "bridges" that connect mRNA codons to the amino acids they encode. One end of each tRNA has a sequence of three nucleotides called an anticodon, which can bind to specific mRNA codons. The other end of the tRNA carries the amino acid specified by the codons.
There are many different types of tRNAs. Each type reads one or a few codons and brings the right amino acid matching those codons.
Ribosomes are the structures where polypeptides (proteins) are built. They are made up of protein and RNA (ribosomal RNA, or rRNA). Each ribosome has two subunits, a large one and a small one, which come together around an mRNA—kind of like the two halves of a hamburger bun coming together around the patty.
The ribosome provides a set of handy slots where tRNAs can find their matching codons on the mRNA template and deliver their amino acids. These slots are called the A, P, and E sites. Not only that, but the ribosome also acts as an enzyme, catalyzing the chemical reaction that links amino acids together to make a chain.
Your cells are making new proteins every second of the day. And each of those proteins must contain the right set of amino acids, linked together in just the right order. That may sound like a challenging task, but luckily, your cells (along with those of other animals, plants, and bacteria) are up to the job.
To see how cells make proteins, let's divide translation into three stages: initiation (starting off), elongation (adding on to the protein chain), and termination (finishing up).
In initiation, the ribosome assembles around the mRNA to be read and the first tRNA (carrying the amino acid methionine, which matches the start codon, AUG). This setup, called the initiation complex, is needed in order for translation to get started.
Elongation is the stage where the amino acid chain gets longer. In elongation, the mRNA is read one codon at a time, and the amino acid matching each codon is added to a growing protein chain.
Each time a new codon is exposed:
•A matching tRNA binds to the codon
•The existing amino acid chain (polypeptide) is linked onto the amino acid of the tRNA via a chemical reaction
•The mRNA is shifted one codon over in the ribosome, exposing a new codon for reading
During elongation, tRNAs move through the A, P, and E sites of the ribosome, as shown above. This process repeats many times as new codons are read and new amino acids are added to the chain.
Termination is the stage in which the finished polypeptide chain is released. It begins when a stop codon (UAG, UAA, or UGA) enters the ribosome, triggering a series of events that separate the chain from its tRNA and allow it to drift out of the ribosome.
After termination, the polypeptide may still need to fold into the right 3D shape, undergo processing (such as the removal of amino acids), get shipped to the right place in the cell, or combine with other polypeptides before it can do its job as a functional protein.
The first step in polypeptide synthesis is the synthesis of the specific mRNA that encodes the polypeptide. (1) The mRNA contains a sequence 237 that mediates its binding to the small ribosomal subunit. This sequence is located near the 5’ end of the mRNA. (2) the mRNA-small ribosome subunit complex now interacts with and binds to a complex ...
The two major steps in creating a protein are transcription and translation. Transcription creates an mRNA molecule, using a DNA sequence as a template. DNA and mRNA are similar, although certainly not identical, molecules. An mRNA sequence is essentially a copy of a DNA sequence with the thymines replaced by uracil.
