Topics to be covered :-

1. Mutation
2.Genetic mutation
3. Chromosomal mutation
4. Genomatic mutation
5. Non disjunction
6. Aneuploidy
7. Euploidy

MUTATION

• Mutation, an alteration in the genetic material (the genome) of a cell of a living organism.
• Mutation is sudden, discontinuous variation in genotype and phenotype of an organism due to change in chromosomes and genes.
• In addition to Recombination mutation is another phenomenon that leads to variation in to vari DNA.
• Factors which are responsible for Mutation :-
  i) Smoking, Radiations, chemicals
  ii) DNA replication error
• The organisms which undergoes mutation is called mutant. The agent of mutation is called mutagen.

Different types of Mutation

Genetic mutations :- changes in gene structure.
Chromosomes mutations:- changes in chromosomes number or structure.

Gene mutation

• It is alteration of DNA due to change in nucleotide sequence. Gene mutation may occur due to change in a single base pair of DNA known as point mutation.
  Example:- Sickle cell anemia
• Change in more than one nucleotide base pair is called gross mutation.

Gene mutation occur by following methods :-
a) Substitution :- incorrect bases matched with each other

b) Insertion :- Addition of one or more bases in nucleotide chain it tcan lead to change in whole sequence of actebbraidings .

c) Deletion :- Removal of base pair from the sequence.

Chromosome mutation

Alteration in the sequence and number of genes on chromosomes can cause such mutations.

• Duplication
  A part of chromosomes is duplicated such that there are more genes on it.
• Deletion
  A part of chromosomes is deleted.
• Inversion
  A part of the chromosomes is broken and added inversely.
• Translocation
  A part of a non homologous chromosomes is attached to the chromosomes and vice versa.

GENOMATIC MUTATION

It is change in chromosome number that bring about visible effects on a the phenotype.
It is of two types:-
Aneuploidy:-
In aneuploidy any change in number of chromosome is an organism would be different than the multiple of basic set of chromosomes .

• It commonly arise due to non-disjunction absence of of separation of tv separation of two homologous chromosomes during of two homologous
  chromosomes during cell division) of the two chromosome of homologous pair.
• So that one gamete comes to have an extra chromosome (n+1) while the other becomes deficient in one chromosome (n-1)
• Fusion of these gametes (n-1 or n+1) with normal gametes (n) give rise to different types of aneuploids.
• Nondisjunction is the failure of homologous chromosomes or sister chromatids to separate properly during cell division.

Example of aneuploidy:-
Trisomy – Down’s syndrome, klinefelter’s syndrome.
Monosomy-turner syndrome.

(b)Euploidy-

• In Euploidy any change in the numbers of chromosomes is the multiple of the numbers of chromosomes is basic set.
•  These may be haploidy or polyploidy. There is only one allele of each gene present t in each cell.

(ii) Polyploidy

• One set of chromosome.
• There is only one allele of each gene present t in each cell.

(iii) Polyploidy

• More than two set of chromosomes
• Failure of cytokinesis after telophase stage of cell division results in an increase is a whole set of chromosomes in an organism and this phenomenon is called as polyploidy.
• It is often seen in plants.
• In case of animals, polyploidy usually results in sterility.
• Therefore polyploidy is rare in animal.