Genetic Code and Mutation - An Overview

Mutations are changes in the DNA sequence that can change the genetic code, leading to variations in traits or genetic disorders. The genetic code is the set of rules by which DNA or RNA sequences are translated into proteins. Mutations can occur naturally or due to environmental factors and may affect protein synthesis. In this article, mutation and genetic code, genetic code, types of mutations, and importance of the mutation and genetic code are discussed. Mutation and Genetic Code is a topic of the chapter Molecular Basis of Inheritance in Biology.

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This Story also Contains

1. What is Mutation and Genetic Code?
2. Genetic Code
3. Types of Mutations
4. Importance of the Mutation and Genetic Code

What is Mutation and Genetic Code?

The genetic code is considered the set of rules by which the information in the DNA sequence is translated into amino acids that form proteins, important in the structure and function of cells. The process, otherwise called protein synthesis, is the basis of all biological processes, and therefore it serves as the foundation of molecular biology.

The genetic code is important in biology because it lines out the mechanisms at the molecular level in life. It is thereby the keystone, not just in explaining how information is passed from one generation to another but underlying the research itself in genetics, biotechnology, and medicine.

Mutation refers to a change in the sequence of DNA molecules, which can either be spontaneous or induced by several environmental factors. Such changes have impacts that range from benign to deleterious and play a critical role in both evolution and diseases.

Genetic Code

The genetic code is the sequence of nucleotides—adenine, cytosine, guanine, and thymine—in DNA or RNA that specifies the amino acid sequence in a protein. The decoding of the genetic code was one of the high points of molecular biology. It was the discovery of a universal shared language of all living creatures.

The components that make up a genetic code are the codons, which are referred to as triplets of nucleotides that specify particular amino acids, and several types of RNA molecules (mRNA, tRNA, and rRNA) that make the process of transcription-translation possible. It is an almost universal code across species, indicating its very ancient origin and its highly fundamental nature in life.

Also Read-

• MCQ on Mutation and Genetic Code
• Molecular Basis of Inheritance
• RNA Processing
• RNA Splicing

Types of Mutations

The change in the DNA sequence affects the amino acid composition of proteins with eventual changes in their structure and function.

Point Mutations

Point mutation is when a single nucleotide base changes in the DNA. These changes might mostly arise during DNA replication or repair processes and may or may not have serious effects on protein synthesis.

Silent Mutations

These are mutations that do not alter the amino acid sequence of the protein. One of the reasons is the redundancy or degeneracy in the genetic code: more than one codon may code for an amino acid. Hence, such a mutation might happen in the non-coding region of the gene or the coding region but without bringing a change in the amino acid encoded.

Missense Mutations

This entails the replacement of one amino acid by another in the synthesis of a protein. This can result in either structural or functional changes in the protein, depending on the particular amino acids and their biochemical properties. Such functional effects of missense mutations could be mild or severe and depend on the place of the mutation within the protein structure and how central this protein is to cellular processes.

Nonsense Mutation

A nonsense mutation introduces a stop codon into the mature mRNA sequence. Such nonsense mutations result in protein truncation, which cuts short the length of the protein, rendering it nonfunctional because premature translation stops. Nonsense mutations typically result in a loss-of-function mutation: the earlier such a mutation occurs within the sequence, the more drastically different the size of the peptide produced is from that of the wild type encoded for by the normal mRNA.

Frameshift Mutation

The frameshift mutation is a mutation that consists of nucleotide insertion or deletion, changing the reading frame of the sequence during expression. The reading frame changes; that is, the codons are regrouped and, hence, a different sequence of amino acid is formed downstream of the mutation.

Insertions

Insertion is a type of mutation when one or more nucleotide base pairs are added to the DNA sequence. This action disrupts the normal reading frame of codon triplets, leading to the incorrect measurement of all downstream codons. This means the protein synthesised either has an entirely different sequence compared to the original, leading to the formation of a non-functional protein in case the insertion disrupts the essential functional domains.

Deletions

Deletions remove one or more nucleotide base pairs from the DNA sequence. As with insertions, this change disrupts the reading frame of the codons downstream from that site. Such an alteration in sequence then can greatly alter the amino acid sequence of the resulting protein, usually causing the protein to be nonfunctional or severely impaired in function.

Importance of the Mutation and Genetic Code

• Medical Applications: Genetic disorders; treatment and diagnosis; medical practice based on an individual's genetic profile.

• Agriculture Application: Improvement of plant variety through genetic engineering to increase yield; resistance to pests and improvements in nutrition.

• Evolutionary Biology: The role of mutation in generating genetic variation; Adapting to changing environments and driving the process of evolution.

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