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Translation in biology is defined as the process of turning nucleic acid information into amino acids. The study of genes, genetic variants, and heredity is part of the molecular foundation of inheritance. The molecular foundation of heredity consists of DNA, RNA, and genetic code. They pass down genetic genes from parents to children.
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Keyterms: Nucleic acid, Amino acids, Genes, Genetic variants, Heredity, Inheritance, DNA, RNA, Genetic code, Cell, Translation, mRNA, tRNA, Proteins, Ribosomes
Read more: Difference between purines and pyrimidines
What is translation?
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The fundamental unit of a living thing is a cell. Similarly, it is commonly accepted that the molecular basis that serves as the fundamental unit of all living creatures is Deoxyribo-Nucleic Acid - DNA. DNA carries almost all of the information needed for an organism to carry out all of the biological, metabolic, and biophysical activities that occur throughout its life cycle.
Translation is defined in Molecular Biology as the process of turning nucleic acid information into amino acids. It also has something to do with the process of making proteins from mRNA templates.
During the translation process, the sequence of nucleotides on the RNA is translated into the amino acid sequence of proteins. Ribosomes carry out the entire translation procedure, where both ribosomes and tRNA dock on a matured mRNA transcript and choose various enzymes in an energy-intensive process that consumes both ATP and GTP.
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Components of Translation
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The translation process is typically carried out within the ribosomes which is a cell organelle. These ribosomes include ribosomal RNA, structural RNAs, and around 80 essential proteins. Ribosomes are referred to as the cell's manufacturing unit due to their role in protein synthesis, i.e. carrying out the translation process.
Ribosomes aid in the synthesis of the amino acid polypeptide bond. They serve as a platform for distinct tRNA molecules transporting specific amino acids and energy molecules like ATP and GTP to congregate in an enclosed region, and since they are close to each other, energetically favourable conditions emerge and amino acid polypeptide chains are formed.
The ribosome also serves as a catalyst for the creation of the peptide bond. Various enzymes in the ribosomes interact with the interacting tRNA and amino acid molecules, playing an important part in the transfer of information from RNA to proteins and in the effective use of energy molecules to carry out the processes. Ribosomal RNA, commonly known as ribozymes, acts as a catalyst in unicellular organisms such as bacteria.
Translation's primary components are as follows:
- mRNA of both Eukaryotes and Prokaryotes
- tRNA aids in the transmission of instructions and information between proteins and nucleic acids in both the Eukaryotes and the Prokaryotes.
- Ribosomes: Because it includes ribosomal RNA and proteins, it is known as the cell's production unit.
- Enzymes are necessary for the creation of a peptide bond between amino acids as well as the attachment of amino acids to the correct tRNA molecules.
- Proteins are soluble factors that are necessary for effective translation initiation, elongation, and termination.
Also Read: NCERT Solutions for Class 12 Biology Molecular Basis of Inheritance
Process of Translation
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Translation occurs in three stages or phases, each of which is linked with a distinct protein. The primary sources of energy in this process are GTP and ATP. The three phases of the translation mechanism are as follows:
- Initiation
- Elongation
- Termination
Initiation
Initiation occurs when the ribosome attaches to the mRNA. This binding occurs at the start codon, which is a three-base stretch consisting of Adenine, Uracil, and Guanine (AUG). Only the initiator tRNA, which contains the methionine amino acid, recognises this beginning code. As a result, in most situations, the sequence of a protein begins with methionine.
Elongation
It is characterised by the sequential addition of amino acids and the creation of a polypeptide chain in a sequence specified by the DNA and reflected by the RNA.
At this stage, complexes composed of amino acids linked to tRNA successively bind to the next three pairs of nucleobases, known as codons, on the mRNA, and the ribosome travels from codon to codon on the mRNA, creating the polypeptide.
Termination
At this point, a release factor binds to stop the codon, causing translation to cease and the polypeptide to be released from the ribosome.
Genetic code
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A nucleic acid is duplicated to produce another nucleic acid during replication and transcription. Both of these processes are mutually beneficial. Translation, conversely, modifies genetic information from a polymer of nucleotides to an amino acid polymer. This is not founded on the concept of complementarity. So, how exactly does this procedure take place?
You've probably seen barcodes on grocery store products. These barcodes serve as identifiers for the object. Scanning the barcode allows the shop to keep track of the item. A genetic code exists in the same manner. It is a collection of instructions on the mRNA that instructs the cell on which amino acid to add to the polymer.
The task of decoding this genetic code was exceedingly difficult and included several experts from various fields as follows:
George Gamow: Scientist who postulated that since four bases (adenine, guanine, cytosine, and uracil) are required to code for 20 amino acids, the genetic code must be a combination of three bases (a triplet). A permutation combination of 43 (4 x 4 x 4) results in 64 codons, which is greater than the number of amino acids.
Har Gobind Khorana: A scientist who invented the chemical technique for synthesising RNA molecules with a specific base combination. These compounds were crucial in cracking the genetic code.
Marshall Nirenberg: A biochemist and geneticist who created a cell-free protein synthesis method that aided in the deciphering of the genetic code.
Severo Ochoa: A scientist who found an enzyme that allowed him to manufacture RNA with specific sequences without using a DNA template.
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| Important Topics Related to the Chapter | ||
|---|---|---|
| DNA Genetic Material | Prokaryotic and Eukaryotic Transcription | Why is DNA negatively charged? |
| Structure of RNA | DNA replication | Model Organism |
| DNA packaging | Bioinformatics | DNA Polymerases |
mRNA untranslated region
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The full length of mature mRNA does not contain codons that are translated into a protein's amino acid sequence. The 5′ end of the RNA has a ‘cap,' two short lengths of untranslated regulatory regions abutting the coding sequence (the 5′ UTR and 3′ UTR), and a polyadenylated tail that can dictate protein sequence without being directly translated.
These untranslated areas are important in mRNA export from the nucleus, enzymatic degradation protection, and translational activity control. They have binding sites for proteins that can promote or decrease translation, as well as docking sites for ribosomes and other translation machinery.
Things to remember
- Translation is the process by which a cell transforms genetic information contained in an mRNA molecule into a protein.
- Messenger RNA (mRNA) is a kind of RNA that transmits genetic instructions on how to build proteins from the cell's DNA to its protein-making machinery.
- mRNA may be a copy of one or smattering genes from a cell's chromosome.
- The translation process is typically carried out within the ribosomes, a cell organelle. These ribosomes include ribosomal RNA, structural RNAs, and around 80 essential proteins.
- Ribosomal RNA, commonly known as ribozymes, acts as a catalyst in unicellular organisms such as bacteria.
Previous Year Questions
- A terminator codon which is called amber is… [COMEDK UGET 2011]
- Clover leaf model of tRNA was suggested by… [JKCET 2010]
- Histone octamer contains… [JKCET 2011]
- Heterogeneous nuclear RNA is converted to… [AMUEEE 2014]
- Who gave semi-conservative mode of DNA replication… [JKCET 2014]
- Adjacent nucleotides are joined by a… [AMUEEE 2015]
- The successive nucleotides of RNA are….[JIPMER 2001]
- When the centromere of a chromosome is located…
- The back bone of RNA consists of…
- When the centromere of a chromosome is…
- Purines found both in DNA and RNA...[NEET 2019]
- Ratio of complementary genes is… [NEET 2001]
- Which form of RNA has a structure resembling clover leaf… [NEET 2004]
- Which RNA is short lived… [COMEDK UGET 2006]
- Who discovered transduction in bacteria?… [COMEDK UGET 2011]
- VNTR stands for… [COMEDK UGET 2006]
- Human genome project was officially started in… [COMEDK UGET 2011]
- Franklin Conrat demonstrated that RNA is the genetic material of… [COMEDK UGET 2007]
- DNA replication is semi-conservative because... [COMEDK UGET 2008]
- DNA packaging in eukaryotes is done by formation of… [CUCET 2011]
Sample Questions
Ques. What is the simple definition of translation in biology? (2 marks)
Ans. Translation in biology is simply the conversion of a sequence of messenger RNA molecules to a sequence of amino acids or proteins. Simply put, translation is the process of converting RNA into protein. The transfer of data from RNA to protein. Normally, this procedure is irreversible, although there are exceptions.
Ques. What are the Three Translation Stages? (2 marks)
Ans. Translation is separated into three major stages. The following are the three steps of process translation:
- Initiation: The stage at which the entire process begins with the ribosome attaching to mRNA.
- Elongation is the movement of the ribosome from codon to codon on mRNA in order to produce the polypeptide.
- Termination: The process is completed and the polypeptide is released from the ribosome.
Ques. Which of the mentioned enzymes is involved in translation? (2 marks)
(A) Aminoacyl tRNA synthetase
(B) 23S rRNA
(C) Peptidyl Transferase
(D) All of the above
Ans. D is the right answer. Aminoacyl tRNA synthetase is responsible for binding the proper amino acid to a tRNA. The bigger component of the bacterial ribosome includes 23S rRNA, which serves as an enzyme, including the peptidyl transferring activity required for polypeptide chain elongation.
Ques. During translation, Are both strands of DNA used as templates for the construction of two new strands of protein? (2 marks)
Ans. No. In the replication process, DNA strands serve as a template for the creation of new DNA strands. DNA is transcribed into RNA during the transcription process. Translation happens after transcription and is the process through which ribosomes produce proteins. mRNA codons are translated into the amino acids that make up the polypeptide chains of proteins during the translation process. As a result, the translation process does not make use of DNA strands as a template. It catalyses amino acid assembly using a strand of mRNA, ribosomes, and tRNA.
Ques. Which is the initial stage of translation in biology? (2 marks)
Ans. The first stage is initiation during the translation process. During this stage, the smaller component of the ribosome may connect with mRNA molecules to start the translation process. The mRNA now comes into touch with a tRNA (transfer RNA), which adds an amino acid called methionine to the mRNA's starting sequence. The amino acid coding sequence begins with a genetic code that encodes for the amino acid methionine. Following this, the bigger subunit of the ribosome enters the picture and attaches to the mRNA to finish the initiation process. This is followed by additional translation stages such as elongation and termination.
Ques. List two essential roles of ribosomes during translation. (2 marks)
Ans. Two essential roles of ribosomes during translation are:
(i) They provide surface for binding of mRNA in the groove of the smaller subunit of ribosome.
(ii) As a larger subunit of the ribosome has peptidyl transferase on its ‘P’ site, therefore, it helps in joining amino acids by forming peptide bonds.
Ques. Explain (in one or two lines) the function of the following: (2 marks)
(a) Promoter
(b) tRNA
(c) Exons
Ans. a. Promoter: It is one of the three components of a transcription unit that takes part in transcription. It is located at the start 5′ end and provides a site for attachment of transcription factors (TATA Box) and RNA polymerase.
- tRNA: It takes part in the transfer of activated amino acids from the cellular pool to the ribosome for their taking part in protein formation.
- Exons: In eukaryotes, DNA is a mosaic of exons and introns. Exons are coding sequences of DNA which are transcribed and translated.
Ques. Briefly describe the following: (2 marks)
(a) Transcription
(b) Polymorphism
(c) Translation
(d) Bioinformatics
Ans.
- Transcription: It is DNA directed synthesis of RNA in which the RNA is transcribed on a 3* → 5’ template strand of DNA in 5’ → 3’ direction.
- Polymorphism: Variation at the genetic level arising due to mutation is called polymorphism. Such variations are unique at a particular site of DNA, forming satellite DNA. The polymorphism in DNA sequences is the basis of genetic mapping and DNA fingerprinting.
- Translation: Protein synthesis from mRNA, tRNA, rRNA.
- Bioinformatics: Computational method of handling and analyzing biological databases.
Ques. If a double-stranded DNA has 20 percent of cytosine, calculate the percent of adenine in the DNA. (2 marks)
Ans. In a DNA molecule, the number of cytosine molecules is equal to guanine molecules & the number of adenine molecules is equal to thymine molecules. As a result, if a double-stranded DNA has 20% of cytosine, it has 20% of guanine. The remaining 60% includes both adenine & thymine which are in equal amounts. So, the percentage of adenine is 30%.
Ques. In the medium where E. coli was growing, lactose was added, which induced the lac operon. Then why does lac operon shut down sometime after the addition of lactose in the medium? (2 marks)
Ans. Lac operon is switched on, on adding lactose in medium, as lactose acts as inducer and makes repressor inactive by binding with it. When the lac operon system is switched on, β-galactosidase is formed, which converts lactose into glucose and galactose. As soon as all the lactose is consumed, the repressor again becomes active and causes the system to switch off (shut down).
Ques. Why is the Human genome project called a megaproject? (2 marks)
Ans. The human genome project is called a megaproject because
(i) It required bioinformatics databases and other high-speed computational devices for analysis, storage and retrieval of information.
(ii) It generated a lot of information in the form of sequence annotation.
(iii) It was carried out in a number of labs and coordinated on an extensive scale.
Ques. What is DNA fingerprinting? Mention its application. (2 marks)
Ans. DNA fingerprinting or DNA typing is a technique of determining nucleotide sequences of certain areas (VNTRs) of DNA which are unique to each individual. Each person has a unique DNA fingerprint. Unlike a conventional fingerprint that occurs only on the fingertips and can be altered by surgery, a DNA fingerprint is the same for every cell, tissue and organ of a person. It cannot be changed by any known treatment. Applications of DNA fingerprinting are as follows:
- Paternity disputes can be solved by DNA fingerprinting.
- DNA fingerprinting technique is being used to identify genes connected with hereditary diseases.
- It is useful in the detection of crime and legal pursuits.
- It can identify racial groups, their origin, historical migrations and invasions.
Ques. Depending upon the chemical nature of the template (DNA or RNA) and the nature of nucleic acids synthesized from it (DNA or RNA), list the types of nucleic acid polymerases. (2 marks)
Ans. (i) DNA dependent DNA polymerase – synthesis.
(ii) DNA dependent RNA polymerase – synthesis.
(iii) RNA dependent DNA polymerase – Retroviral nucleic acid.
(iv) RNA dependent RNA polymerase – cDNA synthesis.
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