Module 1 - Unit 2

One or more nucleotide pairs is inserted into or deleted from the a length of DNA. Insertion and deletion cause dramatic changes in the triplet sequence. These mutations affect the way in which the triplets of bases is "read" during DNA replication. This causes a frameshift. 

Frameshift = The addition or deletion of nucleotides causes a shift in the reading frame of the codons in mRNA --> alterations to the amino acid sequence at translation of DNA replication. Every triplet of bases after the change in the sequence is altered. 

Insertion: 

• Adding a new amino acid, which changes the sequence. 
• Example: Huntington's Chorea = insertion of a triplet nucleotide repeat changes the protein. Damages to the nerve cells in the brain, inherited and progressive disease, which causes loss of motor control and dementia. 

Deletion:

• Removing an amino acid, which changes the sequence. 
• Example: Cystic Fibrosis = deletion of a triplet pair causes the loss of an amino acid. Stickier mucus, which leads to lung congestion and reduced gaseous exchange.