Mutation
Genes of living beings sometimes undergo changes because of different reasons. This change of genes is known as mutation. Mutation can refer to any change in the amount, organization, structure, or content of genetic material. Some gene mutations affect only their carriers, while some are transferred into the descendants of the carriers. The mutation that passes on from the affected one to his or her offspring is known as inherited mutation and is responsible for diversity among species. There are different causes of mutations such as Non-alkylating agents, Hydroxylamine, Nitrous acid, Intercalating agents, Irradiation.
- Non-Alkylating agents:
Formal dehydrate reacts with amine groups of DNA and cross-links DNA, RNA, and portions
- Hydroxylamine:
Hydroxylamine reacts with cytosine to form derivatives that pair with adenine instead of guanine.
- Nitrous Acid:
It oxidatively deaminates cytosines, adenine, and guanine to form uracils, hypoxanthine and xanthenes respectively. These changes result in AT-GC transition.
- Intercalating Agents:
Many intercalating compounds disrupt replication. Some intercalating agents, such as acridines, tend to cause framshift mutation.
- Irradiation
Irradiation happens because of following reasons
- i) UV radiation: includes climerization of adjacent Pyrimidines to particularly adjacent thymine.
- ii) Ionizing Radiation (x-rays and gama rays): it can cause extensive damage to DNA including opening purine rings, which leads to depurination and breaking phosphodiesters bounds.
Types of Mutation
Mutation can be classified following types
a) Missense mutation:
It is possible if base substitution occurs in the coding region of a gene. It results in an amino acid change in protein product of that gene. Example, sickle cell anemia
b) Non-Sense mutation:
It leads to the conversion of an amino acid codon to a stop codon. Translation of the RNA from a gene with non-sense mutation is permanently terminated. Example Thalassemia
c) Frameshift Mutation:
If base pair in gene, for some reasons, is deleted, it causes frameshift mutation.
e) Insertion:
It changes the number of DNA bases in a gene by adding a piece of DNA. The protein made by this mutation may not function properly.
f) Deletion:
It occurs when a piece of DNA is removed and changes the number of DNA base.
g) Duplication:
It occurs when a piece of DNA is copied due to some abnormal reasons. This duplication disrupts the function of resulting protein.
h) Repeat expansion:
It occurs when the number of the times of short DNA sequence repetition is increased due to some reasons. The resultant protein of this mutation does not perform its function properly.
