Mutation and its types
Mutation is a process that produces a gene or chromosome that differs from
the wild type. The mutation may result due to changes either on the gene or the
chromosome itself.
Thus, broadly mutation maybe:
1. Gene mutation where the allele of a gene changes.
2. Chromosome mutation where segments of
chromosomes, whole chromosomes, or
entire sets of chromosomes change.
Types of Mutations
There are various schemes for classification of different kind of mutations. Depending on:
A. The Type of Cell Involved
1. Somatic mutations
• Mutations that are in the somatic tissues of the body.
• Mutations are not transmitted to progeny.
• The extent of the phenotypic effect depends upon whether the mutation is dominant or
recessive (dominant mutations generally have a greater effect).
• The extent of the phenotypic effect depends upon whether it occurs early or late in
development (early arising mutations have a greater effect).
Germinal mutations
, • Mutations that are in the germ tissues of the body.
• Mutations may be transmitted to progeny
• Dominant mutations are seen in first generation after the mutation occurs
• If a female gamete containing an X-linked mutation is fertilized, the males will show
the mutant phenotype
• Recessive mutations will only be seen upon the chance mating with an individual
carrying the recessive allele too; thus, the recessive mutation may remain hidden for
many generations
B. Mode of Origin
(1) Spontaneous mutations
The spontaneous mutations occur suddenly in the nature and their origin is unknown. They
are also called “background mutation” and have been reported in many organisms such as,
Oenothera, maize, bread molds, microorganisms (bacteria and viruses), Drosophila, mice,
man, etc.
(2) Induced mutations
Besides naturally occurring spontaneous mutations, the mutations can be induced artificially
in the living organisms by exposing them to abnormal environment such as radiation, certain
physical conditions (i.e., temperature) and chemicals.
C. Direction of Mutation
According to their mode of direction following types of mutations have been recognised:
1. Forward mutations
In an organism when mutations create a change from wild type to abnormal phenotype, than
that type of mutations are known as forward mutations. Most mutations are forward type.
2. Reverse or back mutations
The forward mutations are often corrected by error correcting mechanism, so that an
Mutation is a process that produces a gene or chromosome that differs from
the wild type. The mutation may result due to changes either on the gene or the
chromosome itself.
Thus, broadly mutation maybe:
1. Gene mutation where the allele of a gene changes.
2. Chromosome mutation where segments of
chromosomes, whole chromosomes, or
entire sets of chromosomes change.
Types of Mutations
There are various schemes for classification of different kind of mutations. Depending on:
A. The Type of Cell Involved
1. Somatic mutations
• Mutations that are in the somatic tissues of the body.
• Mutations are not transmitted to progeny.
• The extent of the phenotypic effect depends upon whether the mutation is dominant or
recessive (dominant mutations generally have a greater effect).
• The extent of the phenotypic effect depends upon whether it occurs early or late in
development (early arising mutations have a greater effect).
Germinal mutations
, • Mutations that are in the germ tissues of the body.
• Mutations may be transmitted to progeny
• Dominant mutations are seen in first generation after the mutation occurs
• If a female gamete containing an X-linked mutation is fertilized, the males will show
the mutant phenotype
• Recessive mutations will only be seen upon the chance mating with an individual
carrying the recessive allele too; thus, the recessive mutation may remain hidden for
many generations
B. Mode of Origin
(1) Spontaneous mutations
The spontaneous mutations occur suddenly in the nature and their origin is unknown. They
are also called “background mutation” and have been reported in many organisms such as,
Oenothera, maize, bread molds, microorganisms (bacteria and viruses), Drosophila, mice,
man, etc.
(2) Induced mutations
Besides naturally occurring spontaneous mutations, the mutations can be induced artificially
in the living organisms by exposing them to abnormal environment such as radiation, certain
physical conditions (i.e., temperature) and chemicals.
C. Direction of Mutation
According to their mode of direction following types of mutations have been recognised:
1. Forward mutations
In an organism when mutations create a change from wild type to abnormal phenotype, than
that type of mutations are known as forward mutations. Most mutations are forward type.
2. Reverse or back mutations
The forward mutations are often corrected by error correcting mechanism, so that an
