Frameshift mutations cause abnormal proteins due to errors in mRNA sequencing, leading to misread codons and incorrect amino acid linking. This can result in various human diseases, including Tay Sachs disease. Frameshift mutations occur from nucleotide insertions or deletions and can cause common diseases like cancer.
A frameshift mutation is a genetic defect that causes abnormal, often nonfunctional proteins to be produced. An error in the sequencing of genetic information causes the cell’s protein synthesis machinery to link amino acids in the wrong order. Frameshift mutations are associated with a number of different human diseases, including Tay Sachs disease.
To understand why a frameshift mutation can cause disease, it helps to understand the basics of how proteins are made. The code for all proteins is in deoxyribonucleic acid (DNA) stored in the nuclei of cells, and this DNA is made up of linked molecules known as nucleotides. To make a protein, the first step is for a molecule known as messenger ribonucleic acid (mRNA) to make a copy of the DNA. The mRNA then travels outside the nucleus and is converted from a nucleotide sequence into a chain of amino acids with the help of structures known as ribosomes, in a process known as translation. Proteins are formed from these chains of amino acids.
During translation, a three-nucleotide sequence of mRNA called a codon specifies which amino acid is to be linked next. It is important to maintain the integrity of the codons so that the ribosome can link the correct amino acids together and form the correct protein. When a frameshift mutation occurs, there is an error in the mRNA sequence that causes the codons to be misread.
For example, a possible mRNA sequence could be UUUAAAGGG, where each letter represents a nucleotide. The normal codons would then be UUU, AAA and GGG. If an error occurs in the mRNA, it can result in the sequence GUUUAAAGGG. The ribosome would read codons such as GUU, UAA and AGG because the frame of reference has been shifted by an extra nucleotide. As a result, either the wrong amino acids would be linked together and the wrong protein would be made, or a codon could be read as a stop signal, thus truncating the protein prematurely.
There are several ways a frameshift mutation can occur. It could occur from the insertion of a nucleotide, or it could also result from the deletion of a nucleotide. If three nucleotides are deleted, this would not be considered a frameshift mutation because the codons that come after the mutation are read normally and have not been shifted out of their normal frames.
Many different human diseases can result from a frameshift mutation. Tay Sachs disease, an inherited condition that typically results in death at a very young age, can be caused by a frameshift mutation. Gene mutations can also be associated with the development of more common diseases, such as different types of cancer.
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