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Mutations

What is mutation?

Mutation is a sudden geritable changein a characteristicof an organism

This sudden change has to be heritable

The term mutation was coined by Hugo De vries in 1900

The word mutation is derived from the latin word ‘Mutare’ means to change

You may also refer other related articles

What is Selection in crop improvement? | Agristudent.com

How mutations take place?

Mutation may be the result of

1. a change in a gene

2. a change in chromosome that involves several genes

3  a change in plasmagene

How are mutations classified?

A. Based on genetic basis of heritable changes

1. Gene mutations

These are produced by change in the base sequence of genes

The change may be due to base substitutions, deletion or addition

2. Chromosomal mutation

These arise due to change in chromosome number that may leads to polyploidy or aneuploidy or change in chromosome structure that result in deletions duplication, inversion and translocation

3. Cytoplasmic or plasmagene mutation

These are due to change in the base sequence of plasma genes

The plasma genes are present in mitochondria or chloroplast

Here the mutant character occurrs in buds or somatic tissues which are used for propagation in clonal crops

B. Based on origin

1. Spontaneous mutations

Mutations occur in natural populations at a low rate (10 to the power 6) but different genes may show different mutation rates

2. Induced mutation

Mutations may be artificially induced by treatment with certain physical or chemical agents

Available evidence indicates that induced mutation rarely produce new alleles they produce alleles which are already known to occur spontaneously

Induced mutations are comparable to spontaneous mutations in their effects and in the variability they produce

Induced mutation occur at a relatively higher frequency so that it is practical to work with them

C. Based on magnitude of phenotypic effects

1. Oligogenic Mutation

Large phenotypic effect and recognizable on individual plant basis and can be seen easily in M2 generations

Eg. Ancon breed in sheep, pod maize to cob maize

2. Micro mutations

Polygenic mutations – Small phenotypic effect which can not be recognized on individual plant basis but can be recognize only in a group of plants

Selection should be done in M3 or later ge nerations

What are the Characteristic feature of mutations

1. Mutations are generally recessive but dominant mutations also occur

2. Mutations are generally harmful to the organism. Most of the mutations have deleterious effects but small proportion (0.1%) of them are beneficial

3. Mutations are random i.e. they may occur in any gene. However some genes show high mutation rates than the others

4. Mutations are recurrent

5. Induced mutations commonly show pleiotropy often due to mutation in closely linked genes

Further readings and references

Jones S. Woolfson A, Partridge L (6 December 2007). “Genetic Mutation”. In Our Time. BBC Radio 4. Retrieved 18 October 2015

Liou, stephanie (5 February 2011) “All About Mutations”. HOPES. Huntington’s Disease Outreach Project for Education at Stanford