genetic bini
TRANSCRIPT
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DNA
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CHROMOSOME
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MUTATION
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TYPES OF MUTATION
Spontaneous and Induced Mutations:
Mutations occurring naturally without any knowncause are called spontaneous mutations.
Mutation caused by mutagens- induced mutation
Somatic and Germinal Mutations:
A mutation occurring in a body cell other than the
reproductive cells is called a somatic mutations.Germinal mutations occur in reproductive tissues
and are passed onto the next generation throughthe gametes.
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Forward and Reverse Mutations:
When a normal gene mutates into its allelethat produces a mutant phenotype, it is calledforward mutation.
When a mutation in the mutant allele restores
the normal phenotype, it is called reversemutation or back mutation, or reversion.
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MUTATIONS:
POINT MUTATIONS:
changes in the nitrogen base pair sequence ofDNA or a gene: base substitution, deletion,
addition (insertion) and nucleotides repeatexpansion.
1. Base Substitution:
Nitrogen base pair of DNA is substituted byanother base pair, it is called base substitution.2 types:
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Transition
When a purine is replaced by other purine or apyrimidine is replaced by the other pyrimidineas follows:
A G or C T
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Transversion
When a purine is replaced by a pyrimidine and viceversa.
A C
T G
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ypes o u a on ue o aseSubstitution
Missence mutation
Silent mutation
Non-sense mutation
Missense mutation:
The new codon causes an incorrect AMINOACID to be inserted into the protein. This effect
on the function of the protein depend on whatis inserted in place of normal amino acid.
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Non-sense mutation:
The new codon causes the protein toprematurely TERMINATE, producing a product
that is shortened and often does not function.
Silent mutation:
Silent mutation does not causes any change in
amino acid. (Silent mutation codes for sameamino acid)
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2. Base Addition and Base Deletion
Deletion:
Mutations that result in MISSING DNA are called
DELETIONS.Deletions can also cause frame-shift mutation
For example
ORIGINAL DELETIONThe fat cat ate the wee rat The fat ate thewee
rat
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Insertions:
Mutations that result in the addition of extra DNA arecalled insertions.
Insertions can also cause frame shift mutations,and general result in a nonfunctional protein.
For example:
ORIGINAL INSERTION:The fat cat ate the wee rat The fat cat xlv ate the
wee
rat
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3. Repeat Expansion:
Nucleotide repeats are short DNA sequencesthat are repeated a number of times in a row.