How do you remember trinucleotide repeats?
- Trinucleotide repeat: GAA (Out of the four, only one to start with letter G).
- Chromosomal mapping of affected gene: Chromosome 9 (Mnemonic: FRIEDRICH has 9 letters).
- Clinical features: Mnemonic – FRIEDREICH’S Ataxia. Foot – Pes cavus. Reflexes (Knee and Ankle jerks) – Absent. Intention tremors.
What are trinucleotide repeat disorders?
Trinucleotide repeat disorders consist of a group of human diseases, which are a result of an abnormal expansion of repetitive sequences and primarily affect the nervous system. These occur during various stages of human development.
How are trinucleotide repeat diseases caused give an example?
For example, Huntington’s disease occurs when there are more than 35 CAG repeats on the gene coding for the protein HTT. A parent with 35 repeats would be considered normal and would not exhibit any symptoms of the disease.
What is the trinucleotide repeat sequence?
The mutation, referred to as “trinucleotide repeat (TNR) expansion,” occurs when the number of triplets present in a mutated gene is greater than the number found in a normal gene [1–3]. Additionally, the number of triplets in the disease gene continues to increase as the disease gene is inherited (Fig. 1a).
What are the two major features of trinucleotide repeat mutations?
Clinical and Genetic Features
Collectively, the common clinical features of trinucleotide diseases include neurodegeneration, ataxia, mental retardation, and muscle weakness or wasting [1]. The average age of onset differs for each disorder and ranges from infancy to adulthood.
How many trinucleotide repeat disorders are there?
When the cause of a disease can be traced to having too many copies of a certain nucleotide triplet in the DNA, the disease is said to be a trinucleotide repeat disorder. Today, there are 14 documented trinucleotide repeat disorders that affect human beings**. Huntington’s Disease is part of this group.
What type of mutation is trinucleotide repeat?
A trinucleotide repeat expansion, also known as a triplet repeat expansion, is the DNA mutation responsible for causing any type of disorder categorized as a trinucleotide repeat disorder. These are labelled in dynamical genetics as dynamic mutations.
How do trinucleotide repeats expand during DNA replication?
As shown in the animation, trinucleotide repeats can expand due to slippage during DNA replication. The number of repeats can therefore increase with each cell division. Expanded repeats are also inherited and can grow longer over multiple …