What Is The Role Of Dna In Protein Synthesis – DNA is a double-stranded molecule consisting of the four nucleobases adenine, cytosine, guanine and thymine; the sum of a cell’s DNA makes up its genome. A gene is a region of an organism’s DNA that is transcribed into a single-stranded RNA molecule in which thymine is converted to uracil and the other bases remain the same.
The RNA transcript is then translated into the amino acid sequence of a protein. Because there are four different nucleobases but twenty amino acids, RNA is translated into codons or triplets of nucleobases according to a mapping called the genetic code (see figure below).
- 1 What Is The Role Of Dna In Protein Synthesis
- 2 Enigmatic Facts About Dna Translation
What Is The Role Of Dna In Protein Synthesis
The genetic code which dictates the conversion of RNA codons into amino acids. Codons are read from the inside of the figure outwards. Image courtesy of J_Alves, Open Clip Art.
How Acidic Amino Acid Residues Facilitate Dna Target Site Selection
DNA can therefore be thought of as a blueprint for storing information that flows from DNA to RNA to protein. This flow of information is called the central dogma of molecular biology, illustrated in the figure below.
Note: Like any dogma, there are times when the central dogma of molecular biology is violated. If you are interested in an example, consider Chapter 4 of Bioinformatics Algorithms.
The central dogma of molecular biology states that genetic information flows from DNA in the nucleus, into the RNA that is transcribed from the DNA, and then to proteins that are translated from the RNA and that then serve some purpose in the cell.
All of your cells have essentially the same DNA, yet your liver cells, heart cells, and brain cells serve different functions. This is because the rates at which your genes are regulated, or converted into RNA and then protein, vary for different cell types and in response to different stimuli.
Dna Binding Mechanism And Evolution Of Replication Protein A
Gene regulation typically occurs at either the DNA or protein level. At the DNA level, regulation is modulated by transcription factors, master regulator proteins that typically bind to the DNA immediately upstream of a gene and serve to either activate or repress the gene’s transcription rate, thereby turning the rate up or down, respectively.
Because of the central dogma, transcription factors are involved in a feedback loop. DNA is transcribed into RNA, which is translated into the protein sequence by a transcription factor, which then binds to the upstream region of a gene and changes its rate of transcription.
Transcription factors are crucial to the cell’s response to its environment because extracellular stimuli can activate a transcription factor via a system of signaling molecules that transmit a signal through relay molecules to the transcription factor (see figure below). Only when the transcription factor is activated will it regulate its target gene(s).
A cell that receives a signal that triggers a response where that signal is “transduced” into the cell, resulting in the transcription of a gene. We will discuss signal transduction in more detail in a future module.
Dna Replication Protein Synthesis Transcription Vector Image
In Module 2, we will discuss the details of how the cell detects an extracellular signal and conveys it as a response within the cell. For now, we will focus on the relationship between transcription factors and the genes they regulate.
A transcription factor has a weak binding affinity for DNA in general, but it has a very strong binding affinity for a single specific short sequence of nucleotides
Called a sequence motif. Think of a transcription factor as latching onto DNA and then sliding up and down the DNA molecule until it finds its target motif where it squeezes. If this motif occurs immediately before a gene, then the transcription factor will regulate that gene.
Note: The astute reader will note that we have already used the term “motif” in two different contexts, first to mean both a recurrent network substructure and now to mean a sequence of nucleotides to which a transcription factor binds. This sequence is called a “motif” because the transcription factor can regulate multiple genes such that the binding sequence will occur immediately before most or all of these genes.
Enigmatic Facts About Dna Translation
A natural question is therefore to find the set of genes to which a transcription factor binds. A common experiment that answers this question is called ChIP-seq
, which is short for chromatin immunoprecipitation sequencing. This approach, illustrated in the figure below, combines an organism’s DNA with multiple copies of a protein of interest that binds to DNA (which in this case would be a transcription factor). After allowing the proteins to bind naturally to the DNA, the DNA is cleaved into much smaller fragments of a few hundred base pairs. As a result, we obtain a collection of DNA fragments, some of which are attached to a copy of our protein of interest.
The question is how to isolate the fragments of DNA bound to a transcription factor of interest, and the clever trick is to use an antibody. Normally, antibodies are produced by the immune system to target foreign pathogens. The antibody used by ChIP-seq is designed to bind to our protein of interest, and the antibody is attached to a bead. Once the antibody binds to the protein target, a complex is formed consisting of the DNA fragment, the protein bound to the DNA, the antibody bound to the protein and the bead bound to the antibody. Because the bead weighs down these complexes, they can be filtered out as precipitates from the solution, and we are left with only the DNA fragments bound to our protein.
In a final step, the protein is uncoupled from the DNA, leaving a collection of DNA fragments that were previously bound to a single protein. Each fragment is read using DNA sequencing to determine the order of nucleotides, which are then queried against the genome to determine the gene(s) that the fragment precedes. When the protein is a transcription factor, we can therefore assume that it is the genes that the transcription factor regulates!
Dna, Genes & Chromosomes Overview
If you would like a different explanation, you may also want to check out the following excellent video on identifying genes that are regulated by a transcription factor. This video was produced by students in the 2020 PreCollege Program in Computational Biology at Carnegie Mellon. The presenters won an award from their peers for their work, and for good reason!
STOP: How do you think scientists could determine whether a transcription factor activates or represses a given gene?
As a result of techniques such as ChIP-seq, researchers have learned a great deal about which transcription factors regulate which genes. The key is to organize the relationships between transcription factors and the genes they regulate in a way that helps us identify patterns in those relationships. EVERYTHING ON Earth is made of atoms, most of which are tightly packed together in the form of minerals. Life can be used for minerals – ask a coral reef – but its essence lies in atoms arranged as separate molecules and the way they interact.
Biological molecules are characterized in different ways. One is that they can be very large. The simple inorganic molecules that make up the air and oceans typically contain only a few atoms, and often only two or three. Many biological molecules contain thousands. A few contain billions. These molecules are not just large, they are also precisely structured. Moreover, these structures can be recreated with atom-by-atom accuracy.
Nucleic Acid Sequence
These distinctly lifelike properties stem from the fact that biological molecules have purposes bestowed upon them by evolution. For example, life needs molecules that can catalyze chemical reactions and molecules that can store and transfer the genetic information needed to make those catalysts. These requirements are met by two kinds of large molecules: proteins, which do most of the catalysis, as well as much else, and nucleic acids, which mostly store and transmit information.
Nucleic acids and proteins are both linear polymers; long, unbranched strings of components that look alike, like paper chains at a children’s party or beads on a necklace. In both cases, the range of component “monomers”—the paper chain links or beads—is limited. Nucleic acids are made of only five different monomers, known as nucleotides; proteins are typically made of 20 different varieties of amino acids. In both cases, the assembly of the chains is done one link at a time using a specific type of chemical reaction. Nucleotides are linked together by what are called ester bonds; proteins using what are called peptide bonds.
This linear, modular approach means that the same machinery can make many different molecules. All that is required is a system that can catalyze the addition of a new monomer to the elongating chain, a way to tell the system what kind of monomer to add next, and some dogged persistence. A typical human protein is about 400 amino acids long; some are much longer. DNA molecules, one of life’s two types of nucleic acid, are much longer still. The shortest DNA molecules found in humans are about 17,000 nucleotides long; the longest consist of over 100m.
The order in which these nucleotides appear determines what information is stored in the DNA. The order of the different amino acids determines the shape of the protein that is created from them by
Topologically‐interlocked Minicircles As Probes Of Dna Topology And Dna‐ Protein Interactions
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