The definition of a point mutation is when a single nucleotide base is changed, inserted, or deleted from a sequence of DNA or RNA. These types of mutations will have several kinds of effects on the final protein product, and these consequences are moderately predictable depending on the specifics of the mutation. They can range from absolutely benign to catastrophic when it comes to the production, function, and composition of that protein.

What Causes a Point Mutation?

Point mutations usually occur during DNA replication. This is when one double-stranded DNA molecule creates two single strands of DNA, which are a template for the creation of the complementary strand. However, when a point mutation takes place, the entire DNA sequence can be altered. If only one purine o pyrimidine changes, it will change the amino acid that these nucleotides were coding.

Sometimes spontaneous mutations happen during the DNA replication that will end up in a point mutation. The odds of this taking place can go up depending on the exposure to mutagens. For instance, exposure to high radiation levels or chemicals.

These mutagens are many times linked to cancer and other diseases, because the effects they can have on DNA molecules and strands, can lead to errors in replication, where changes can range from substitution, insertion, or deletion mutations.

What Happens When a Point Mutation Occurs?

When point mutations take place in non-coding sequences, in most cases they won’t have consequences. But, if the mutated base pair is located in the promoter sequence of a gene, then there’s a higher possibility of the expression of the gene changing. Or, if it takes place in the splicing site of an intron, then this may cause interference with the correct splicing of the transcribed pre-mRNA.

If only one amino acid is altered, then the entire peptide can also change, leading to the entire protein change as well. This is a key issue, because if that particular protein has a function in the reproductive process of the cell, then this can lead to severe changes in the cell of the organism.

This doesn’t necessarily mean that the changes will be harmful; they can lead to adaptations in the environment where the organism lives. These mutations can create advantages that can be passed from generation to generation, ensuring the survival of that species by improving and benefiting the population.

On the other hand, it can also lead to the organism becoming weaker and lowering its chances of survival; so you can say that a point mutation’s effects can go either way in the way it will affect the life of an organism. Some of these point mutations won’t lead to permanent changes in the organism that can be passed on through generations, but they can result in diseases or malformations.

Which Diseases are Caused by Point Mutations?

There are many diseases that can be traced to point mutations in specific proteins in already identified genes. Some of them are quite common and some are extremely rare.

Diseases such as cancer, neurofibromatosis, sickle-cell anemia, Tay-Sachs disease, color blindness, are all caused by point mutations.