A substitution mutation, also known as a point mutation, involves the replacement of a single nucleotide in DNA or RNA, leading to potential changes in protein synthesis without altering the number of bases. There are different types of substitution mutations, including silent, missense, and nonsense mutations, with varying effects on proteins, such as causing diseases like sickle-cell anemia and cystic fibrosis. Factors contributing to these mutations include errors during DNA replication and exposure to mutagens.

1. SUBSTITUTION
MUTATION
NUCLEAR ACID AND PROTEIN SYNTHESIS

2. DEFINITION OF INSERTION
• Substitution mutation is also known as point mutation in this type of genetic
mutation a single nucleotide is
• replaced by the another nucleotide in DNA or RNA sequence.
• This type of mutation doesn’t cause a difference in the number of bases like
insertion or deletion mutations do. Substitution mutations just switch out one or
more bases for different ones.

3. OCCURRENCE OF SUBSTITUTION MUTATION
• A substitution mutation occurs when specific bases (A, T, C or G) in a gene are
swapped for different ones. A substitution mutation replaces one base with another,
resulting in a change in only one chemical letter. This transition might be caused by a
variety of factor relating to the storage and reading of DNA.
• Nucleotides tend to come off during the depurination process.
• Because there are just four nucleotides to pick from, the proteins that handle DNA are
prone to making mistakes while replacing them.
• During DNA replication, the two strands of the DNA molecule separate, and each
strand serves as a template for the synthesis of a new complementary strand.

4. • Occasionally, errors can occur during DNA replication, leading to
the incorporation of an incorrect nucleotide. For example, the DNA
polymerase may mispair a nucleotide during the synthesis of the
new strand, resulting in a substitution mutation.
• For example; The blood disease Sickle-cell anemia is caused by a
simple substitution mutation. In the mutation, a single nucleotide is
replaced in the portion of DNA which codes for a unit of
hemoglobin. Hemoglobin is a multi-protein complex, responsible
for carrying oxygen and supporting the shape of blood cells.

5. CAUSES
• Exposure to mutagens (alkylating agents or x-rays)
• ➤DNA damage (oxidative stress or exposure to reactive species
• Deamination(a amino group is removed from nucleotide base resulting in
different base)
• ➤ Errors during replication process

6. TYPES.
There are 4 types of substitution
1. Silent mutation
2. Missense mutation
3. Nonsense mutation
4. Frame shift mutation

7. SILENT MUTATION
• Silent mutations are mutations in DNA sequence that do not have an observable
effect on the organism’s phenotype.
• They are a specific type of neutral mutation.
• They don’t have effects on gene function.
• In silent mutation the change in the DNA sequence of the gene has no effect on
the amino acid sequence.
• For example, AAA (codes for the amino acid lysine, Lys) being mutated to AAG
(which also codes for Lys).

8. MISSENSE MUTATION
• A missense mutation is a DNA change that results in different amino acids being
encoded at a particular position in the resulting protein.
• Some missense mutations alter the function of the resulting protein.
• In this case the altered codon still code for the amino acids that make sense but
this sense may not b right.
• Missense mutations can render the resulting protein nonfunctional, and such
mutations are responsible for human disease.
• For example; Epidermolysis bullosa a group of rare diseases that cause the skin
to be fragile and to blister easily

9. FRAME SHIFT MUTATION
• Frame shift mutations also known as base pair insertion or deletions. A frameshift mutation in a
gene refers to the insertion or deletion of nucleotide bases in numbers that are not multiples of
three.
• The mRNA reads as a series of nucleotides triple during translation therefore insertion or
deletions of nucleotides may alter the frame of genetic message therefore these mutations
called frame shift mutations.
• This is important because a cell reads a gene’s code in groups of three bases when making a
protein.
• For example; Two frameshift mutations (one is the insertion of two nucleotides and the other
deletion of one nucleotide) in the CFTR genes result in cystic fibrosis. The CFTR gene regulates
the proper flow of ions, i.e., chloride and sodium across the sell membrane.

10. EFFECTS IF SUBSTITUTION
• A change in amino acid codon coding to a specific stop codon produces an
unfinished protein that is typically non-functional. This can result in silent mutations,
in which a codon shift encodes the same amino acid but no modifications are made
to the protein formed.
• Variation is a codon that encodes a different amino
• acid, resulting in a slight change in the protein generated; sickle-cell anemia is an
example of this. A substitution mutation can displace many more than one nucleotide.
In this case, it may make the
• protein completely dysfunctional, or give it an entirely new function..

11. •Thanks