3. Mutation
• Spontaneous and Induce Mutation
• Point Mutation (Silence, Missense, Nonsense)
• Frameshift Mutation
4. Transposon
• Jumping gene
• Segments of DNA that can move around to different
positions in the genome of a single cell.
5. Errors of enzyme function
• DNA polymerase enzymes
• Recombination enzymes
• DNA repair enzymes
6. Spontaneous and Induce Mutation
Spontaneous
• A result of natural changes in DNA structure
• All types of point mutation can occur spontaneously
Induce
• Result from changes caused by environmental chemicals or
radiation
7. Genome mutation
• changes in the number of chromosomes
Chromosome mutation
• change the order of the genes within the chromosome.
(deficiency, deletion, inversion, duplication, translocation)
Gene or point mutation
• changes in the base sequence in a gene
8. Mutagen
- Any environmental agent that significantly increases the
rate of mutation above the spontaneous rate
• Types of mutations
1. substitutions
2. deletions
3. insertion
9. Substitution
• Substitution mutations are a type of mutation in which a single
nucleotide is substituted with a different nucleotide.
• Substitution mutation is sometimes referred to as point mutation.
• However, point mutation is defined particularly as a type of
mutation involving a change of only one nucleotide.
10. A base pair in the wild type allele may be replaced by
by another base in the mutant allele.
There are two situations!
Transition
• Occur when a purine is substituted with another purine or a
pyrimidine is substituted with another pyrimidine ( A to G or G
to A, T to C or C to T)
Transversion
• When a purine is substituted for a pyrimidine or a pyrimidine
replaces a purine (T to C or A to G)
11. Substitution mutations may also be typified into:
silent mutations,
missense mutations and
nonsense mutations.
12. Silent mutation
• If a base substitution occurs in the third position of the codon
there is a good chance that a synonymous codon will be
generated.
• Thus, amino acid sequence encoded by the gene is not changed
and the mutation is said to be silent
13. Missense mutation
• When base substitution results in the generation of a codon that
specifies a different amino acid and hence leads to a different
polypeptide sequence
14. Nonsense mutation
• When a base substitution results in a stop codon ultimately
trucating translation and the most likely leading to a nonfunctional
protein
15. Deletion
• One or more base pairs are lost from DNA
• One or two bases are deleted the translational frame is altered
resulting in grabled message and non functional product
• Deletion of three or more bases leave the reading frame intact
• A deletion of one or more codons results in a protein missing
one or more amino acids. This may be deleterious or not
16. Insertion
• The insertion of additional base pairs may lead to frameshifts
depending on whether or not multiples of three base pairs are
inserted.
• Combination of insertion and deletions leading to a variety of
outcomes are also possible.
17. Point Mutation
• A point mutation is a genetic mutation where a single nucleotide base is
changed, inserted or deleted from a sequence of DNA or RNA.
• Point mutation occurs when a base pair of a gene is changed.
• Point mutation may also pertain to substitution mutation when one
nucleotide is substituted with a different nucleotide.
• Point mutations are the most common types of mutation and there are
two types;
1.transition
2.transversion
18. • Point mutation occurring in noncoding sequences often does not
result in an altered amino acid sequence during translation.
• However, if a mutation in the promoter sequence of a gene occurs,
the effect may be apparent since the expression of the gene may
cause changes in the amino acid sequence, as well as the structure
and function of the protein product.
• Sometimes, point mutation also covers mutations caused by single
nucleotide insertions or deletions (which are types of frameshift
mutation).
• Point mutations that occur in DNA sequences encoding proteins
are either silent, missense or nonsense
19.
20. Frameshift Mutation
• A mutation caused by the addition or deletion of a base pair or base
pairs in the DNA of a gene resulting in the translation of the genetic
code in an unnatural reading frame from the position of the mutation
to the end of the gene.
