Question

What are the four types of Mutations?

Answer 1

Sudden heritable change in genetic material of an organism is called mutation. Mutation is a discontinuous source of variation. Mutation word was given by Hugo De Vries. De Vries studied Mutations in the plant Oenothera lamarckiana (evening primrose), it is a hybrid plant. According to De Vries the Mutations are of two types of variations in evolutions:
1. Continuous variations: These are minor variations developed by crossing over/meiosis/sexual reproduction, these variations are developed in every generation of an organism.
2. Discontinuous variations: This includes both minor and major types of variations, these are developed by Mutations and suddenly appear in any generation.

Complete answer:
Mutations are divided into 2 broad categories:
1.Chromosomal mutation
2.Gene Mutation
A. Chromosomal Mutation:
Changes in number or structure of chromosomes.
It is of 2 types:
1.Heteroploidy/Genomic mutation:change in chromosome number.
It is further divided into 2 types:
a. Euploidy: In this the change in number of sets/loss or addition of sets of chromosomes.
b. Aneuploidy:change in number of chromosomes in a set.
2. Chromosomal aberration: change in structure of chromosome.
It is further divided into 4 types:
a. Deletion: Loss of a part or segment of chromosome which leads to loss of some gene is called deletion.
b. Inversion: The Breakage of chromosomal segment but they reunite on the same chromosome but in reverse orders. It leads to change in distance between genes on chromosome or sequence of genes on chromosome so crossing over is affected.
c. Duplication: Occurrence of a chromosomal segment twice on a chromosome.
d. Translocation: Also known as illegitimate crossing over(illegal crossing over), in this a part of the chromosome is broken and may be joined with a non homologous chromosome. This is also known as illegitimate crossing over(illegal crossing over)
B. Gene mutation or point mutation:
It is of 2 types:
1. Substitution
2. Frameshift mutation
1. Substitution: Replacement of one nitrogenous base by another nitrogenous base is called substitution. It causes change in one codon in the genetic code which leads to change in one amino acid in the structure of protein.
Eg. Sickle cell anemia.
2. Frameshift mutation: Some chemicals eg. Accredited , proflavin causes loss or addition of one or two nitrogenous bases in the structure of DNA so complete reading of genetic code is changed. It leads to change in all amino acids in the structure of protein so a new protein is formed which is completely different from previous protein.
So frameshift Mutations are more harmful as compared to substitution.

Note:
Most mutations are harmful but in some cases they can be lethal which leads to death of organisms and sometimes they are beneficial which are used to obtain good varieties of plants and animals. It is called Mutation Breeding. Most of the time mutations are recessive and being recessive, they are never eliminated from a population. It is called Hardy-Weinberg law, this law is applicable to large populations and random mating