Genetic Code Codons Amino Acids: Types, Properties, Key Points
The genetic code is the set of rules by which information encoded in genetic material (DNA or RNA sequences) is translated into proteins. Check this article to know more about the Genetic Code Codons Amino Acids.
Jasdeep Bhatia12 Jun, 2024
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The topic “Genetic Code Codons Amino Acids” will be covered in this article. Inheritance is based on genetic information that is passed from parent to child. Transcription and translation come next, and the process starts with DNA replication. The genetic data contained in the DNA is copied into another form of RNA during transcription. The complementary base pairs of the two nucleic acids control the entire process. However, the genetic code, not complimentary, governs the latter translation process. Translating nucleic acid information into amino acids is known as translation. This article will discuss the property of genetic code, types of amino acids, codons, and exceptions to the code.Introduction
The genetic code contains all the information needed to produce a protein from RNA. The order of amino acid base pairs determines how proteins are created. As a result, altering this order can impact how amino acids are created. For scientists, deciphering the genetic code was a significant problem. George Gamow, a physicist, proposed a technique to overcome this difficulty. He used permutation and combination theories to crack this genetic code. He proposed that the genetic code be composed of three nucleotides that can be translated into 20 amino acids and four bases. A triplet codon of four nitrogenous bases and three nucleotides codes for one amino acid. This means that there are a total of 64 amino acids that could exist. But 20 amino acids are present in nature.Genetic Code Example
The nitrogenous bases Adenine (A), Guanine (G), Cytosine (C), and Thymine are stored as a straight, evenly spaced, and non-overlapping sequence on any one of DNA's two strands (T). The code words are represented by these abbreviation letters. Codons, a three-letter word, make up the genetic code words. The order of these letters corresponds to the length of the DNA strand. Each codon consists of a different arrangement of these letters. They will be seen as a single amino acid after they are incorporated into a polypeptide chain. They can create up to 64 codons using only the special combinations of four words. Codon nucleotides are read by cells, which also decode mRNAs. Three-stop codons combined denote the end of a protein, three-start codons denote the beginning of a protein and encode the amino acid methionine, and most codons define an amino acid. During translation, cells read messenger RNA's (mRNA) codons from the start codon to the finish codon.Properties of Genetic Code
Triplet Code
A codon or a code word is a set of nucleotides that designate an amino acid. Strong evidence supports the idea that a triplet, or a sequence of three nucleotides, codes for an amino acid in a protein. Three-base codons are created using the four nucleotide bases (A, G, C, and U). Sense codons are among the 64 codons (that specify amino acids). There are 64 codons for 20 amino acids since each codon denotes the existence of more than one coding for a particular amino acid.Polarity
Each triplet is read from 5' to 3', with the first base being 5', the middle base being 3, and the last base being 3. This suggests that the polarity of the codons is fixed and that if the codon were read backward, the base sequence would change and define two different proteins.Degenerate Code
Every amino acid, except tryptophan (UGG) and methionine (AUG), is encoded by a different codon; this characteristic is referred to as the degeneracy of the genetic code. For instance, in yeast mitochondria, UGA codes for tryptophan.Start and Stop Codons
The initiating or starting codon is often the AUG codon. Either prokaryotes (methionine) or eukaryotes (start the polypeptide chain) (N- formylmethionine). UAG, UAA, and UGA, on the other hand, are referred to as termination codons or stop codons. These never encode for any amino acids and are not read by any tRNA molecules.Unambiguous and Universal
Because the genetic code is unambiguous, each codon will only ever code for one single amino acid. Additionally, it has been determined that all species share the same genetic code, making them universal.Nonoverlapping code
A nucleotide that is a part of one triplet never becomes a part of the following triplet when the code is read sequentially in groups of three. For example, 5’-UCU-3’ codes for Serine 5’-AUG-3’ codes for methionineAmino Acid Codon Table
The transmission of genetic information from a parent to the offspring makes it possible for traits to be inherited. DNA replication, transcription, and translation are the first steps in transferring genetic information. The genetic data stored in DNA is copied into RNA during the transcription process. The ribosome completes the translation process by pairing amino acids as directed by messenger RNA (mRNA), using tRNA (transfer RNA) molecules to deliver amino acids, and reading the mRNA’s three nucleotides simultaneously. The 64-entry amino acid codon table is similar in all organisms; thus, the genetic code is the same for the smallest and largest organisms. The genetic code table lists relationships between codons and amino acids that summarise an organism's genetic code.Types of Amino Acids
The many types of amino acids created based on the codons that the cell translates are shown in the codon table. Below is a list of all 20 amino acids' names and abbreviations. Alanine =Ala Arginine =Arg Asparagine=Asn Aspartic acid =Asn Cysteine =Cys Glutamic acid =Glu Glutamine =Gln Glycine =Gly Histidine =His Isoleucine =Ile Leucine =Leu Lysine =Lys Methionine =Met Phenylalanine =Phe Proline =Pro Serine =Ser Threonine =Thr Tryptophan =Trp Tyrosine =Tyr Valine =ValCodons
Specific amino acids are designated by RNA codons. The amino acid that will be generated depends on the arrangement of the bases in the codon sequence. There are three different codon locations that any one of the four RNA nucleotides could occupy. There are 64 potential codon combinations as a result. Three codons (UAA, UAG, and UGA) act as stop signals to indicate the completion of protein synthesis out of the sixty-one codons that specify amino acids. The start signal for translation is the codon AUG, which codes for the amino acid methionine. Numerous codons can specify the same amino acid. For instance, the codons UCU, UCC, UCA, UCG, AGU, and AGC specify the amino acid serine. The RNA codon table above lists the codon combinations and assigned amino acids. According to the table, the codon UAC designates the amino acid tyrosine if uracil (U) is in the first codon position, adenine (A) is in the second, and cytosine (C) is in the third.Protein Production
DNA transcription and translation are the processes that result in the production of proteins. Before being immediately translated into proteins, DNA information must first be transcribed into RNA. The process in which genetic information is transferred from DNA to RNA during protein synthesis is known as DNA transcription. The enzyme RNA polymerase can only transcribe a single strand of DNA into a single-stranded RNA polymer known as messenger RNA because certain proteins known as transcription factors unwind the DNA strand (mRNA). Guanine pairs with cytosine, and adenine pairs with uracil when RNA polymerase transcribes the DNA. The mRNA molecule must pass through the nuclear membrane to reach the cytoplasm since transcription takes place in the nucleus of a cell. Once in the cytoplasm, transfer RNA, ribosomes, and mRNA work together to convert the message transcribed into amino acid chains. Each RNA codon is read during translation, and transfer RNA then adds the corresponding amino acid to the expanding polypeptide chain.How Mutations Affect Codons
A gene mutation modifies the DNA nucleotide sequence. This mutation may impact a single nucleotide pair or larger chromosomal segments. The majority of the time, changing nucleotide sequences causes proteins to malfunction. This is because altered codons result from altered nucleotide sequences. If the codons are altered, the proteins that are made won't contain the amino acids that were originally coded for in the gene sequence. Point mutations and base-pair insertions or deletions are the two main categories of gene mutations. A single nucleotide is changed via point mutations. When nucleotide bases are added to or subtracted from the original gene sequence, base-pair insertions or deletions result. The most frequent outcomes of these two types of events are gene mutations. First, mutations can be brought on by environmental variables like chemicals, radiation, and UV light from the sun.Exceptions to the Code
Most genes in microbes and plants share START and STOP signals and similar codon assignments to identical amino acids, proving that the genetic code is universal. There are several exceptions, though; most involve associating one or two of the STOP codons with an amino acid. In addition, even though GUG is intended for valine, both the codons AUG and GUG may code for methionine as a beginning codon. This violates the non-ambiguousness property. Thus, only a few codes frequently deviate from the global or unambiguous code.Key Points
- The information in an organism's genetic code is stored as coded information on DNA or genes.
- Transcription is the process of moving data from DNA to mRNA.
- The translation is converting information from mRNA into an amino acid.
- Three nucleotides with four nitrogenous bases apiece make up a codon.
- Triplet codons are used to code for amino acids.
- More than one codon is used to code for some amino acids. We refer to this as degeneracy.
- Three of the 64 possible codons mark the completion of a protein but do not code for amino acids, making a total of 64 possible codons.
- The AUG codon, which specifies the amino acid methionine and marks the start of a protein, is the first codon in every mRNA.
- The codons are read starting with the start codon after reaching a stop codon. The genetic code is simple, redundant, and universal.
- The three amino acids arginine, leucine, and serine have the most codons.
Genetic Code Codons Amino Acids <span style=
Q1. How do codons determine amino acids?
Ans: The order of amino acids in a protein, from the N-terminus (methionine) to the C-terminus, is determined by mRNA codons, which are read from 5' to 3'. Each set of three mRNA nucleotides determines an amino acid read during translation (or provides a stop signal indicating that translation is finished).
Q2. Which amino acid contains the most codons?
Ans: The three amino acids arginine, leucine, and serine have the most codons. Six distinct codons will code for each of these amino acids. These three amino acids are the only ones with this many codons.
Q3. Where are codons found?
Ans: An mRNA or DNA both contain codons. They are three-nucleotide sequences that specify an amino acid by name. The tRNA (transfer RNA) molecules, which aid in bringing the amino acids to the mRNA during translation, include anticodons.
Q4. What codon is the most crucial?
Ans: Therefore, it would seem that for specifying the amino acids in proteins, P2 in codons is most significant, P1 is of moderate value, and P3 is least relevant (7). correlation between the G+C (GC) content of the three codon sites and the GC content of the entire genomic DNA of different animals.
Q5. What function do codons serve?
Ans: A DNA or RNA molecule that codes for a particular amino acid through a group of three successive nucleotides. Start, stop, or termination codons are the names given to these.
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