The changes in the single base or nucleotide in the nucleotide sequence and thus changing its complementary base also it is called as point mutations, while when there are insertions or deletions of more than one base pair in the nucleotide sequence it is known as frameshift mutations.
Mutations can be defined as any kind of change in the nucleotide sequence or genetic code, which altering the gene structure as well as the amino acids and the proteins too. These mutations occur in the DNA sequence and affect the sequence during transcription and translation. Therefore mutations disturb the number or order of the base pair in DNA.
The chemical or substances which can induce the mutations are known as mutagens. Though not every mutation results in a negative impact, they can be unnoticed as they might be coding for the same amino acid even after mutation, while some mutations can be effective too as they cause disease like Tay Sachs, Sickle Cell Anemia, etc.
We all are used to of the changes in everyday life, hence DNA (the genetic code) is also not exempted from these gradual changes though it is said that the DNA is highly stable with regard to the nucleotide sequences and composition and each and every work of central dogma that is from replication to transcription and translation is done with high fidelity.
Hereby with keeping the focus on the topic of mutations, we will be discussing the two types of mutations, how they differ from each other and their types and effects.
Content: Point Vs Frameshift Mutations
|Basis for Comparison||Point Mutations||Frameshift Mutations|
|Meaning||When there is a replacement of one base or a single nucleotide from another in the nucleotide sequence and ultimately brings changes in the complementary base also, it results in point mutations.||When there is an insertion or deletion of the numbers of base pairs from the DNA it results in the frameshift mutations.|
|Occurs due to||Alterations in the single nucleotide.||Alterations in numerous nucleotides.|
|It brings changes in the||Structure of a gene because of the substitutions with another base pair.||It changes the number of nucleotides due to either insertions or deletions of the nucleotides.|
|Types||Transitions and Transversions.||Insertions and Deletions.
|Disease caused by changes||It causes Sickle Cell Anemia.||It causes Tay-Sachs disease.|
Definition of Point Mutations
In the simple words, we can say that the replacement of the one base or base pair in the nucleotide sequence of the gene it is called as the point mutations. Point mutations rarely cause any change in the nucleotide sequence. This is also called as the single-base substitution. It occurs because of the mistake occurred during the DNA replication and changes are seen at transcription or translation level.
Further, at the time of transcription when RNA is synthesized from the DNA and then into protein (translation), point mutations generally hinder the final product and thus functional imbalance arise. There are two sub-types of the point mutations, Transitions, and Transversion.
Transition: In this type of mutations, the purines (adenine and guanine) is replaced by another purines or pyrimidines (uracil, thymine, and cytosine) is replaced by another pyrimidine.
Transversion: In this type of mutation, the alteration is between purine to pyrimidine or vice versa, which means the purine is replaced by the pyrimidine or pyrimidine is replaced by purine.
Effects of Point Mutations
The changes in any of the single nucleotide may cause the following effect:
1. Silent Mutation – This mutation does not show any effects in the production of the amino acid as the changed nucleotide, may also code for the same amino acid. Like for example UCA codes for Serine and after mutation in the third base UCU, still the amino acid will be Serine only. These mutations are due to the degeneracy of genetic code and do not show any detectable effects.
2. Missense Mutation – This mutation may bring the change in amino acid, as UCA codes for Serine, but a change in the first base like ACA will code for Threonine. In such cases when the properties of the changed amino acid (charge, polarity, etc.) remains same then these mutations are called conservative, while if the properties of the changed amino acid differs from the earlier one it is called as non-conservative.
There is no change in function of the protein in case of conservative, while in non-conservative the resulting protein might be partially acceptable or unacceptable with regard to protein function and can lead to disease like Sickle-cell anemia.
3. Nonsense Mutation – This type is mutation is known for altering the normal functional amino acid into a stop codon, which results in termination of the protein chain. Like for example, UCA (Serine) changes to UAA (termination codon). This gives the stop signal to the synthesis of the protein chain and effects the function of protein too.
Definition of Frameshift Mutations
A frameshift mutation occurs when there any insertion or deletion of more than one base pairs in the DNA and thus affects the nucleotide sequence and thus changes the amino acids too.
Insertion Mutation: This type of mutation occurs when there is an insertion or addition of extra base pair to the nucleotide sequence.
Deletion Mutation: This type is opposite to the insertion one, where the base pair gets deleted from the sequence which results in changes in the protein products.
Effects of Frameshift Mutations
The deletions or insertions of a base pair in the sequence causes the altered reading frame of the mRNA. This happens because the reading machinery does not recognize the changes in the sequences that whether any base is absent or is added and so there is absent of punctuations in the reading codons and the process of translation continues. This process ultimately changes the process of protein production and can prematurely terminate the chain also.
Key Differences Between Point and Frameshift Mutations
Given below are the critical differences between the two types of mutations occurring in the base pairs of the DNA structure of a gene:
- Point mutations happen when there is a replacement of one base pair from another, while Frameshift mutations occur when there is an insertion or deletion of the base pairs from the DNA structure.
- Point mutations occur due to alterations in the single nucleotide, whereas frameshift occurs due to alterations in numerous nucleotides.
- Point mutation brings changes in the structure of a gene because of the substitutions with another base pair, on the contrary, frameshift mutations change the number of nucleotides due to either insertions or deletions of the nucleotides.
- Transitions and Transversions are the types of point mutations while Insertions and Deletions are the types of frameshift mutations.
- Point mutations cause Sickle Cell Anemia as it brings changes in the structure of the gene, whereas frameshift mutations cause Tay-Sachs disease as it results in the changes in the number of base pairs in the DNA structure of a gene.
In the above article, we studied about the mutation occurring in the DNA sequence, where some changes may be highly effective, while some may be negligible. However, even we are unaware of the changes that occur in our body in order to fight against any disease and adapt according to the surroundings, though our genetic material is highly conserved and our genetic machinery work precisely to save it in every aspect.