Mutation 2

Type of point mutation:
Broadly, there are many types of genetic mutations happens in a genome, however, the point mutations mainly are of three types- either addition/deletion or base substitution.
(a) Addition or deletion: An addition mutation occurs when a single base is inserted into a gene while a deletion mutation occurs when a single base is deleted from a gene.
The addition or deletion mutation generally results in reading frame alteration thus are mostly frame shift mutations.
(b) Base substitution mutation: When a single base is replaced by unlike base, the type of mutation is called base substitution mutation. It can be divided broadly into two categories.
(c) Transition vs transversion: The transition mutation occurs when pyrimidine bases are substituted with the pyrimidine bases or purine bases are substituted with the purine bases.
The transversion mutation occurs when purine bases substitute for pyrimidine bases or vice verse.
• Purine to purine/ pyrimidine to pyrimidine = transition point mutation
• Purine to pyrimidine/ pyrimidine to purine = transversion mutation

[2] Chromosome mutations: These are the changes in the structure or the numbers of chromosomes are called chromosomal mutation. Examples of the alterations in the structure of some parts of the chromosome are duplication, deletion, translocation and inversion. Chromosomal mutation can happen during mitosis and meiosis when chromosomes are condensed and pulled apart. It also occurs during crossing over.
Chromosomal mutation
Any change in the number or length/arrangement of the chromosomes is called chromosomal mutation.
Change in number can be divided in to two-
[A] Change in the length/arrangement of the chromosomes
(i) Deletion of deficiency:- The loss of chromosomal segment. It can be terminal or intercalary.
(ii) Duplication:- The repetition of one more segments is called duplication.
(iii) Inversion:- the number of genes in a chromosome not altered but the sequence of the genes is changed by the rotation of the gene block within a chromosome by 180˚.
(iv) Translocation: transfer of a block of gene from one linkage group to another is called translocation.
[B] Change in chromosome number:
(i) Euploidy: Haploidy(N) – having one set of chromosome number. Diploidy (2N) - Having two set of chromosome number. Polyploidy (Nx): having more than two sets of chromosome number.
(ii) Aneuploidy: Change involving the number of chromosome in a set.
Monosomic- 2N-1, Double monosomy= 2N-1-1, Nullisomic: 2N-2
Hyperploidy:- (Polysomy), Trisomy:2N+1, Tetrasomy: 2N+2.
Thus we can say that mutations are the raw materials for speciation and evolution.

Видео Mutation 2 канала Dr. B. M. Singh