Mutation with Ploidy

MUTATION:
Mutation is sudden change in the hereditary of an organism due to change in number of chromosome, structure of chromosome or change in molecular level of DNA.
Mutation was coined by Hugo De Vries, a Dutch Botanist. He worked on Evening Primrose and observed 834 mutation out of 54343 plants.
Mutation which occurs naturally is called spontaneous mutation where the mutation which occurs artificially by chemicals or physical agents are called as induced mutation. The agents that induce mutation like mustard gas, x-rays, alpha, Betta or gamma rays are called mutagens.The product of mutation is called mutant.

TYPES OF MUTATION:
1) MICRO MUTATION/GENE MUTATION/POINT MUTATION:
Gene mutation is defined as change in the structure of individual gene.It induces just one or two bases in DNA molecule.Thus its is also called as Point Mutation.Gene mutation occurs due to following change in DNA and RNA:

a) Frameshift Mutation:
The mutation which is caused by either addition or deletion of nitrogenous bases of DNA or m RNA is called as Frameshift Mutation.One deletion is neutralized by one addition or vice versa.
i)Addition Mutation:
The point mutation caused by the addition of one base pair of a gene is called addition mutation.
Eg:Addition of G on base sequence:
GAT GAT GAT
addition of G
GAT GGA TGA
ii)Deletion Mutation:
The point mutation caused by deletion of one base pair of gene is called deletion mutation.
Eg,Deletion of G on base sequence
GAT GAT GAT
? deletion of G
GAT ATG ATG

b) Substitution Mutation:
One base pair replaced by a different one is called substitution mutation.It is of two types:
i) Transition:
The mutation which occurs by the substitution of one purine by another purine or one pyrimidine by another is called Transition.
Purine(A,G)
Pyrimidine9C,T0
A--G
C--T
ii)Transversion:
The mutation which occurs by the substitution of one purine by another pyrimidine or vice versa is called Transversion.
Eg;
A -T
C-G

2) CHROMOSOMAL MUTATION/MACRO MUTATION/LINE MUTATION
The mutation which is caused by the change in structure or number of chromosome is called chromosomal mutation.It is of two types:
a)Chromosomal abbreviation:
The mutation which is caused by the change in the structure of chromosome is called chromosomal abbreviation.These are of following types:
i)Deficiency:
Loss of terminal segment from a chromosome is called Deficiency.Eg
ABCDEF-ABCD
Ii) Deletion:
Loss of intercalary segment of chromosome is called Deletion.
Eg.
ABCDEF-ABEF
iii)Duplication:
Sometime the part of chromosome gets repeated in the same chromosome called duplication.Eg
ABCDEFGH-ABCDEFEFGH
Iv)Inversion:
Segment of chromosome being inverted and reunited is called inversion.
Eg:
ABCDEF?ADCBEF
v)Translation:
Exange of segment between non homologous chromosome is called translation..
Eg.
ABCDEFGH/MNOPQRST?ABCDEFST/MNOPQRGH

b)Genomatic mutation or Ploid:
Mutation caused by the change in the number of chromosome is called Ploidy or Genomatic mutations.It is of following type:
A)ANEUPLOIDY:
The addition or loss of one or more chromosome from the complete set is called Aneuploidy.Thus the total number of chromosome is not an exact multiple of the haploid number(n).
Eg(2n+1) Trisomy or (2n-1)monosomy

TYPES OF ANEUPLOIDY:
1)Hypoploidy:
Loss of chromosome for complete set.It is of following types:
i)Monosomics:
Loss of one chromosome from complete set is called monnosomics.It is represented as 2n-1.
ii)Nullisomic:
Loss of single pair of chromosoms from a pair of complete set is called nullisomics.Its is represented by 2n-2.

2)Hyperploidy:
Addition of chromosome in complete set.It is of following type:
i)Trisomic:
Addition of one chromosome is called trisomic.It is represented as 2n+1.
ii)Tetrasomic:
Additon of a pair of chromosome is called tetresomic.It is represented as 2n+2.

B)EUPLOIDY:
It include addition or loss of complete one set or more than one set of chromosome in diploid organism.The total number of chromosome is exact multiple of halploid number.They are of following type:
a)Monoploidy:
It involves loss of one set of chromosome from a diploid set resulting offspring having only one set of chromosome.
Eg:Male wasp,bee
b)Polyploidy:
Addition of one or more sets of chromosome is called polyploidy.Organism with more than two sets of chromosomes is called polyploidy.
Types of Polyploidy:
i)Autopolyploidy:
Autopolyploidy are those polyploids which are derived from the multiplication of the same basic set of chromosome.Autopolyploidy is formed due to replication of chromosomes during interphase and separation of chromatids during anaphase but fails to cytoplasmic cleave during cytokinesis.Autoploids are more fertile,vigour and large sized.
If a diploid species has two sets of chromosomes (AA) an autoploid willl have four similaf genome(AAAA)
Eg:Plum,Strawberry,grapes
ii)Alloploidy:
The polyploidy formed due to doubling of chromosomes number in a F1 hybrid which is derived from two distinct species is called alloploidy.
SpeciesX * SpeciesY
AA BB

AB diploid F1 hybrid

AABB

Cause of polyploidy:
It occurs in nature due to failure of chromosome to separate at the time of anaphase either due to non disjunction or due to non formation of spindle.
Advantages of Polyploidy:
1)Polyploidy is often associated with advantageous features such as increased size,hardness and resistance.This is called hybrid vigour.
2)Polyploidy is one of the source of Variation and help in evolution of new Varieties.
3)Seedless variety of watermelon,tomatoes,grapes etx have been produced by triploids.
4)Desease resistant and high yielding species of crop plants such as hybrid wheat,hybrid paddy are produced by allopolyploidy.
5)Polyploid plants have more morphological genetical and physiological advancement over a normal diploid plant.
6)Polyploid plant often faces the ecological hazards more boldly.

Reason for Triticum aestivum to become Hexaploid:
A Hexaploid species of wheat was artificially synthesized in 1946.A species of wheat Triticum monococcum(2n=14) was bred with wild grass Aegilops speltoids(2n=14) to produce a different species of wheat called emmer wheat(Triticum durum 2n=28),a tetraploid condition. Emmer wheat is again crossed with another species of wild grass Aegilops squarrosa(2n=14) to produce the wheat Triticum aestivum (2n=42) a hexaploid(6n) condition.
Triticum monococcum X Aegilops speltoids
2n=14 2n=14
Triticum durum
4n= 28

Triticum durum X Aegilops squarrosa
4n=28 2n=14


Triticum aestivum
6n=42
Hexaploid condition

ARTIFICIAL INDUCTION OF POLYPLOIDY:
Conchicine is the mostly and widely used chemical for artificial induction of polyploidy.It inhibits the formation of spindle fibre during mitosis.It is greatly used in horticulture because plants treated with it are more resistant.

CAUSES OF MUTATION:
Mutation may occur naturally and is called spontaneous mutation.But if the mutation is induced artificially with the help of chemical agents then it is called induced mutation.The main cause of mutation is chemical agents like mustard gas,X-rays,UV radiations etc called mutagens.These chemical agents are responsible for causing mutation.

MUTATION FREQUENCY:
The rate at which mutation occurs is called mutation frequency.It is very low in most organism.Genes with rapid mutation rate is called mutable or unstable gene.

ROLE OF MUTATION IN EVOLUTION:
1)Mutation provides a bulk of hereditary variations on which natural selection operates.
2)Mutation helps the organism to adjust in the new environment condition.
3)Various new plants of desired character have been created by mutation.
4)Useful characters can be introduced in the organism.
5)High production of disease resisting varieties of crops.
6)Mutation are useful for understanding the basic principles of inheritance.

RESULTS OF MUTATION:
Mutation produces different types of effects like lethal,advantageous ,neutral visible or invisible.Mutation may produce sudden and large changes or may produce small and insignificant changes.the mutation that produce any significant visible changes are detected and the mutations that fail to produce any phenotypic variation are lost undetected .Certain mutation induce physiological changes.they may influence the inability or fertility of organism.
A mutation generally results in the loss of function of genes such as:
1)Mutation changes the sequence of nitrogenous bases in the gene that cause the change in codons and the alters the sequence of amino acids.Therefore,the mutated polypeptide chain may have modified or reduced or no functional activity.
2)Mutation may lead to the formation of a termination of an incomplete polypeptide chain.This lead to the loss of normal functioning of genes.